Replacing tantalum capacitors with ceramic capacitors


Opto Tinker
 

Hi,


On the Tektronix 7904 PSU converter board, there are two tantalum electrolytic capacitors of 0.1uF. Can I substitute them with ceramic capacitors?


Since the tantalum capacitors are a lot more expensive, the original design must put them there on purpose. What could a 0.1 uF tantalum capacitor do that a 01 uF ceramic capacitor cannot?


Thanks!


Stuart Brorson <sdb@...>
 

Some old LDO circuits were unhappy when loaded by high-quality caps.
The old circuits relied on the ESR of the cap to maintain the feedback
stability margin, and if the ESR was too low, the margin went away and
the circuit would oscillate. There is an old TI app note discussing
this behavior here:

http://www.ti.com/lit/wp/snoa842/snoa842.pdf

I don't know if the Tek board has this problem or not.

Besides the ESR issue, as long as the voltage rating of the new cap
meets or exceeds that of the Ta cap, I can't think of any reason not
to substitute. I do suggest using an NPO cap since it's the best
dielectric with the best temp stability, and no piezoelectric effect.
If you do get oscillations after substituting, consider putting a 1/2
ohm resistor in series with the cap.

Stuart

On Thu, 17 Dec 2015, optotinker@yahoo.com [TekScopes] wrote:

Hi,


On the Tektronix 7904 PSU converter board, there are two tantalum electrolytic capacitors of 0.1uF. Can I substitute them with ceramic capacitors?


Since the tantalum capacitors are a lot more expensive, the original design must put them there on purpose. What could a 0.1 uF tantalum capacitor do that a 01 uF ceramic capacitor cannot?


Thanks!







------------------------------------
Posted by: optotinker@yahoo.com
------------------------------------


------------------------------------

Yahoo Groups Links




 

| | This email has been sent from a virus-free computer protected by Avast.
www.avast.com |

Take note that ceramic capacitors change value with voltage.  So a de-rate the voltage appropriately. 


From: "Stuart Brorson sdb@cloud9.net [TekScopes]" <TekScopes@yahoogroups.com>
To: "optotinker@yahoo.com [TekScopes]" <TekScopes@yahoogroups.com>
Sent: Thursday, December 17, 2015 5:33 PM
Subject: Re: [TekScopes] Replacing tantalum capacitors with ceramic capacitors

  Some old LDO circuits were unhappy when loaded by high-quality caps.
The old circuits relied on the ESR of the cap to maintain the feedback
stability margin, and if the ESR was too low, the margin went away and
the circuit would oscillate. There is an old TI app note discussing
this behavior here:

http://www.ti.com/lit/wp/snoa842/snoa842.pdf

I don't know if the Tek board has this problem or not.

Besides the ESR issue, as long as the voltage rating of the new cap
meets or exceeds that of the Ta cap, I can't think of any reason not
to substitute. I do suggest using an NPO cap since it's the best
dielectric with the best temp stability, and no piezoelectric effect.
If you do get oscillations after substituting, consider putting a 1/2
ohm resistor in series with the cap.

Stuart

On Thu, 17 Dec 2015, optotinker@yahoo.com [TekScopes] wrote:

Hi,


On the Tektronix 7904 PSU converter board, there are two tantalum electrolytic capacitors of 0.1uF. Can I substitute them with ceramic capacitors?


Since the tantalum capacitors are a lot more expensive, the original design must put them there on purpose. What could a 0.1 uF tantalum capacitor do that a 01 uF ceramic capacitor cannot?


Thanks!








------------------------------------
Posted by: optotinker@yahoo.com
------------------------------------


------------------------------------

Yahoo Groups Links



#yiv9796327001 #yiv9796327001 -- #yiv9796327001ygrp-mkp {border:1px solid #d8d8d8;font-family:Arial;margin:10px 0;padding:0 10px;}#yiv9796327001 #yiv9796327001ygrp-mkp hr {border:1px solid #d8d8d8;}#yiv9796327001 #yiv9796327001ygrp-mkp #yiv9796327001hd {color:#628c2a;font-size:85%;font-weight:700;line-height:122%;margin:10px 0;}#yiv9796327001 #yiv9796327001ygrp-mkp #yiv9796327001ads {margin-bottom:10px;}#yiv9796327001 #yiv9796327001ygrp-mkp .yiv9796327001ad {padding:0 0;}#yiv9796327001 #yiv9796327001ygrp-mkp .yiv9796327001ad p {margin:0;}#yiv9796327001 #yiv9796327001ygrp-mkp .yiv9796327001ad a {color:#0000ff;text-decoration:none;}#yiv9796327001 #yiv9796327001ygrp-sponsor #yiv9796327001ygrp-lc {font-family:Arial;}#yiv9796327001 #yiv9796327001ygrp-sponsor #yiv9796327001ygrp-lc #yiv9796327001hd {margin:10px 0px;font-weight:700;font-size:78%;line-height:122%;}#yiv9796327001 #yiv9796327001ygrp-sponsor #yiv9796327001ygrp-lc .yiv9796327001ad {margin-bottom:10px;padding:0 0;}#yiv9796327001 #yiv9796327001actions {font-family:Verdana;font-size:11px;padding:10px 0;}#yiv9796327001 #yiv9796327001activity {background-color:#e0ecee;float:left;font-family:Verdana;font-size:10px;padding:10px;}#yiv9796327001 #yiv9796327001activity span {font-weight:700;}#yiv9796327001 #yiv9796327001activity span:first-child {text-transform:uppercase;}#yiv9796327001 #yiv9796327001activity span a {color:#5085b6;text-decoration:none;}#yiv9796327001 #yiv9796327001activity span span {color:#ff7900;}#yiv9796327001 #yiv9796327001activity span .yiv9796327001underline {text-decoration:underline;}#yiv9796327001 .yiv9796327001attach {clear:both;display:table;font-family:Arial;font-size:12px;padding:10px 0;width:400px;}#yiv9796327001 .yiv9796327001attach div a {text-decoration:none;}#yiv9796327001 .yiv9796327001attach img {border:none;padding-right:5px;}#yiv9796327001 .yiv9796327001attach label {display:block;margin-bottom:5px;}#yiv9796327001 .yiv9796327001attach label a {text-decoration:none;}#yiv9796327001 blockquote {margin:0 0 0 4px;}#yiv9796327001 .yiv9796327001bold {font-family:Arial;font-size:13px;font-weight:700;}#yiv9796327001 .yiv9796327001bold a {text-decoration:none;}#yiv9796327001 dd.yiv9796327001last p a {font-family:Verdana;font-weight:700;}#yiv9796327001 dd.yiv9796327001last p span {margin-right:10px;font-family:Verdana;font-weight:700;}#yiv9796327001 dd.yiv9796327001last p span.yiv9796327001yshortcuts {margin-right:0;}#yiv9796327001 div.yiv9796327001attach-table div div a {text-decoration:none;}#yiv9796327001 div.yiv9796327001attach-table {width:400px;}#yiv9796327001 div.yiv9796327001file-title a, #yiv9796327001 div.yiv9796327001file-title a:active, #yiv9796327001 div.yiv9796327001file-title a:hover, #yiv9796327001 div.yiv9796327001file-title a:visited {text-decoration:none;}#yiv9796327001 div.yiv9796327001photo-title a, #yiv9796327001 div.yiv9796327001photo-title a:active, #yiv9796327001 div.yiv9796327001photo-title a:hover, #yiv9796327001 div.yiv9796327001photo-title a:visited {text-decoration:none;}#yiv9796327001 div#yiv9796327001ygrp-mlmsg #yiv9796327001ygrp-msg p a span.yiv9796327001yshortcuts {font-family:Verdana;font-size:10px;font-weight:normal;}#yiv9796327001 .yiv9796327001green {color:#628c2a;}#yiv9796327001 .yiv9796327001MsoNormal {margin:0 0 0 0;}#yiv9796327001 o {font-size:0;}#yiv9796327001 #yiv9796327001photos div {float:left;width:72px;}#yiv9796327001 #yiv9796327001photos div div {border:1px solid #666666;height:62px;overflow:hidden;width:62px;}#yiv9796327001 #yiv9796327001photos div label {color:#666666;font-size:10px;overflow:hidden;text-align:center;white-space:nowrap;width:64px;}#yiv9796327001 #yiv9796327001reco-category {font-size:77%;}#yiv9796327001 #yiv9796327001reco-desc {font-size:77%;}#yiv9796327001 .yiv9796327001replbq {margin:4px;}#yiv9796327001 #yiv9796327001ygrp-actbar div a:first-child {margin-right:2px;padding-right:5px;}#yiv9796327001 #yiv9796327001ygrp-mlmsg {font-size:13px;font-family:Arial, helvetica, clean, sans-serif;}#yiv9796327001 #yiv9796327001ygrp-mlmsg table {font-size:inherit;font:100%;}#yiv9796327001 #yiv9796327001ygrp-mlmsg select, #yiv9796327001 input, #yiv9796327001 textarea {font:99% Arial, Helvetica, clean, sans-serif;}#yiv9796327001 #yiv9796327001ygrp-mlmsg pre, #yiv9796327001 code {font:115% monospace;}#yiv9796327001 #yiv9796327001ygrp-mlmsg * {line-height:1.22em;}#yiv9796327001 #yiv9796327001ygrp-mlmsg #yiv9796327001logo {padding-bottom:10px;}#yiv9796327001 #yiv9796327001ygrp-msg p a {font-family:Verdana;}#yiv9796327001 #yiv9796327001ygrp-msg p#yiv9796327001attach-count span {color:#1E66AE;font-weight:700;}#yiv9796327001 #yiv9796327001ygrp-reco #yiv9796327001reco-head {color:#ff7900;font-weight:700;}#yiv9796327001 #yiv9796327001ygrp-reco {margin-bottom:20px;padding:0px;}#yiv9796327001 #yiv9796327001ygrp-sponsor #yiv9796327001ov li a {font-size:130%;text-decoration:none;}#yiv9796327001 #yiv9796327001ygrp-sponsor #yiv9796327001ov li {font-size:77%;list-style-type:square;padding:6px 0;}#yiv9796327001 #yiv9796327001ygrp-sponsor #yiv9796327001ov ul {margin:0;padding:0 0 0 8px;}#yiv9796327001 #yiv9796327001ygrp-text {font-family:Georgia;}#yiv9796327001 #yiv9796327001ygrp-text p {margin:0 0 1em 0;}#yiv9796327001 #yiv9796327001ygrp-text tt {font-size:120%;}#yiv9796327001 #yiv9796327001ygrp-vital ul li:last-child {border-right:none !important;}#yiv9796327001


Stuart Brorson <sdb@...>
 

Not all ceramic caps are created equal. The voltage change depends
upon ceramic type. That's why I recommend NPO for this application --
they change hardly at all (<1%). Here's an example app note:

http://www.cde.com/resources/catalogs/ceramperf.pdf

Googling around will reveal more info.

I try to never use anything other than NPO (or film) caps in a signal
path. X7R and below are for decoupling, or non-critical
applications.

Stuart


On Fri, 18 Dec 2015, machine guy machineguy59@yahoo.com [TekScopes] wrote:


| | This email has been sent from a virus-free computer protected by Avast.
www.avast.com |

Take note that ceramic capacitors change value with voltage. So a de-rate the voltage appropriately.


From: "Stuart Brorson sdb@cloud9.net [TekScopes]" <TekScopes@yahoogroups.com>
To: "optotinker@yahoo.com [TekScopes]" <TekScopes@yahoogroups.com>
Sent: Thursday, December 17, 2015 5:33 PM
Subject: Re: [TekScopes] Replacing tantalum capacitors with ceramic capacitors

Some old LDO circuits were unhappy when loaded by high-quality caps.
The old circuits relied on the ESR of the cap to maintain the feedback
stability margin, and if the ESR was too low, the margin went away and
the circuit would oscillate. There is an old TI app note discussing
this behavior here:

http://www.ti.com/lit/wp/snoa842/snoa842.pdf

I don't know if the Tek board has this problem or not.

Besides the ESR issue, as long as the voltage rating of the new cap
meets or exceeds that of the Ta cap, I can't think of any reason not
to substitute. I do suggest using an NPO cap since it's the best
dielectric with the best temp stability, and no piezoelectric effect.
If you do get oscillations after substituting, consider putting a 1/2
ohm resistor in series with the cap.

Stuart

On Thu, 17 Dec 2015, optotinker@yahoo.com [TekScopes] wrote:

Hi,


On the Tektronix 7904 PSU converter board, there are two tantalum electrolytic capacitors of 0.1uF. Can I substitute them with ceramic capacitors?


Since the tantalum capacitors are a lot more expensive, the original design must put them there on purpose. What could a 0.1 uF tantalum capacitor do that a 01 uF ceramic capacitor cannot?


Thanks!








------------------------------------
Posted by: optotinker@yahoo.com
------------------------------------


------------------------------------

Yahoo Groups Links



#yiv9796327001 #yiv9796327001 -- #yiv9796327001ygrp-mkp {border:1px solid #d8d8d8;font-family:Arial;margin:10px 0;padding:0 10px;}#yiv9796327001 #yiv9796327001ygrp-mkp hr {border:1px solid #d8d8d8;}#yiv9796327001 #yiv9796327001ygrp-mkp #yiv9796327001hd {color:#628c2a;font-size:85%;font-weight:700;line-height:122%;margin:10px 0;}#yiv9796327001 #yiv9796327001ygrp-mkp #yiv9796327001ads {margin-bottom:10px;}#yiv9796327001 #yiv9796327001ygrp-mkp .yiv9796327001ad {padding:0 0;}#yiv9796327001 #yiv9796327001ygrp-mkp .yiv9796327001ad p {margin:0;}#yiv9796327001 #yiv9796327001ygrp-mkp .yiv9796327001ad a {color:#0000ff;text-decoration:none;}#yiv9796327001 #yiv9796327001ygrp-sponsor #yiv9796327001ygrp-lc {font-family:Arial;}#yiv9796327001 #yiv9796327001ygrp-sponsor #yiv9796327001ygrp-lc #yiv9796327001hd {margin:10px 0px;font-weight:700;font-size:78%;line-height:122%;}#yiv9796327001 #yiv9796327001ygrp-sponsor #yiv9796327001ygrp-lc .yiv9796327001ad {margin-bottom:10px;padding:0 0;}#yiv9
796327001 #yiv9796327001actions {font-family:Verdana;font-size:11px;padding:10px 0;}#yiv9796327001 #yiv9796327001activity {background-color:#e0ecee;float:left;font-family:Verdana;font-size:10px;padding:10px;}#yiv9796327001 #yiv9796327001activity span {font-weight:700;}#yiv9796327001 #yiv9796327001activity span:first-child {text-transform:uppercase;}#yiv9796327001 #yiv9796327001activity span a {color:#5085b6;text-decoration:none;}#yiv9796327001 #yiv9796327001activity span span {color:#ff7900;}#yiv9796327001 #yiv9796327001activity span .yiv9796327001underline {text-decoration:underline;}#yiv9796327001 .yiv9796327001attach {clear:both;display:table;font-family:Arial;font-size:12px;padding:10px 0;width:400px;}#yiv9796327001 .yiv9796327001attach div a {text-decoration:none;}#yiv9796327001 .yiv9796327001attach img {border:none;padding-right:5px;}#yiv9796327001 .yiv9796327001attach label {display:block;margin-bottom:5px;}#yiv9796327001 .yiv9796327001attach label a {text-decoration:
none;}#yiv9796327001 blockquote {margin:0 0 0 4px;}#yiv9796327001 .yiv9796327001bold {font-family:Arial;font-size:13px;font-weight:700;}#yiv9796327001 .yiv9796327001bold a {text-decoration:none;}#yiv9796327001 dd.yiv9796327001last p a {font-family:Verdana;font-weight:700;}#yiv9796327001 dd.yiv9796327001last p span {margin-right:10px;font-family:Verdana;font-weight:700;}#yiv9796327001 dd.yiv9796327001last p span.yiv9796327001yshortcuts {margin-right:0;}#yiv9796327001 div.yiv9796327001attach-table div div a {text-decoration:none;}#yiv9796327001 div.yiv9796327001attach-table {width:400px;}#yiv9796327001 div.yiv9796327001file-title a, #yiv9796327001 div.yiv9796327001file-title a:active, #yiv9796327001 div.yiv9796327001file-title a:hover, #yiv9796327001 div.yiv9796327001file-title a:visited {text-decoration:none;}#yiv9796327001 div.yiv9796327001photo-title a, #yiv9796327001 div.yiv9796327001photo-title a:active, #yiv9796327001 div.yiv9796327001photo-title a:hover, #yiv9796327001
div.yiv9796327001photo-title a:visited {text-decoration:none;}#yiv9796327001 div#yiv9796327001ygrp-mlmsg #yiv9796327001ygrp-msg p a span.yiv9796327001yshortcuts {font-family:Verdana;font-size:10px;font-weight:normal;}#yiv9796327001 .yiv9796327001green {color:#628c2a;}#yiv9796327001 .yiv9796327001MsoNormal {margin:0 0 0 0;}#yiv9796327001 o {font-size:0;}#yiv9796327001 #yiv9796327001photos div {float:left;width:72px;}#yiv9796327001 #yiv9796327001photos div div {border:1px solid #666666;height:62px;overflow:hidden;width:62px;}#yiv9796327001 #yiv9796327001photos div label {color:#666666;font-size:10px;overflow:hidden;text-align:center;white-space:nowrap;width:64px;}#yiv9796327001 #yiv9796327001reco-category {font-size:77%;}#yiv9796327001 #yiv9796327001reco-desc {font-size:77%;}#yiv9796327001 .yiv9796327001replbq {margin:4px;}#yiv9796327001 #yiv9796327001ygrp-actbar div a:first-child {margin-right:2px;padding-right:5px;}#yiv9796327001 #yiv9796327001ygrp-mlmsg {font-size:13px;font
-family:Arial, helvetica, clean, sans-serif;}#yiv9796327001 #yiv9796327001ygrp-mlmsg table {font-size:inherit;font:100%;}#yiv9796327001 #yiv9796327001ygrp-mlmsg select, #yiv9796327001 input, #yiv9796327001 textarea {font:99% Arial, Helvetica, clean, sans-serif;}#yiv9796327001 #yiv9796327001ygrp-mlmsg pre, #yiv9796327001 code {font:115% monospace;}#yiv9796327001 #yiv9796327001ygrp-mlmsg * {line-height:1.22em;}#yiv9796327001 #yiv9796327001ygrp-mlmsg #yiv9796327001logo {padding-bottom:10px;}#yiv9796327001 #yiv9796327001ygrp-msg p a {font-family:Verdana;}#yiv9796327001 #yiv9796327001ygrp-msg p#yiv9796327001attach-count span {color:#1E66AE;font-weight:700;}#yiv9796327001 #yiv9796327001ygrp-reco #yiv9796327001reco-head {color:#ff7900;font-weight:700;}#yiv9796327001 #yiv9796327001ygrp-reco {margin-bottom:20px;padding:0px;}#yiv9796327001 #yiv9796327001ygrp-sponsor #yiv9796327001ov li a {font-size:130%;text-decoration:none;}#yiv9796327001 #yiv9796327001ygrp-sponsor #yiv9796327001ov l
i {font-size:77%;list-style-type:square;padding:6px 0;}#yiv9796327001 #yiv9796327001ygrp-sponsor #yiv9796327001ov ul {margin:0;padding:0 0 0 8px;}#yiv9796327001 #yiv9796327001ygrp-text {font-family:Georgia;}#yiv9796327001 #yiv9796327001ygrp-text p {margin:0 0 1em 0;}#yiv9796327001 #yiv9796327001ygrp-text tt {font-size:120%;}#yiv9796327001 #yiv9796327001ygrp-vital ul li:last-child {border-right:none !important;}#yiv9796327001







------------------------------------
Posted by: machine guy <machineguy59@yahoo.com>
------------------------------------


------------------------------------

Yahoo Groups Links




 

| | This email has been sent from a virus-free computer protected by Avast.
www.avast.com |

Thanks, I did not know that COG ceramics were stable with voltage.  Also thanks for the link which shows the change one can expect from X7R and below.  You have just proven I don't know everything after all, lol.


From: "Stuart Brorson sdb@cloud9.net [TekScopes]" <TekScopes@yahoogroups.com>
To: "machine guy machineguy59@yahoo.com [TekScopes]" <TekScopes@yahoogroups.com>
Sent: Friday, December 18, 2015 7:17 AM
Subject: Re: [TekScopes] Replacing tantalum capacitors with ceramic capacitors

  Not all ceramic caps are created equal. The voltage change depends
upon ceramic type. That's why I recommend NPO for this application --
they change hardly at all (<1%). Here's an example app note:

http://www.cde.com/resources/catalogs/ceramperf.pdf

Googling around will reveal more info.

I try to never use anything other than NPO (or film) caps in a signal
path. X7R and below are for decoupling, or non-critical
applications.

Stuart

On Fri, 18 Dec 2015, machine guy machineguy59@yahoo.com [TekScopes] wrote:


| | This email has been sent from a virus-free computer protected by Avast.
www.avast.com |

Take note that ceramic capacitors change value with voltage. So a de-rate the voltage appropriately.


From: "Stuart Brorson sdb@cloud9.net [TekScopes]" <TekScopes@yahoogroups.com>
To: "optotinker@yahoo.com [TekScopes]" <TekScopes@yahoogroups.com>
Sent: Thursday, December 17, 2015 5:33 PM
Subject: Re: [TekScopes] Replacing tantalum capacitors with ceramic capacitors

Some old LDO circuits were unhappy when loaded by high-quality caps.
The old circuits relied on the ESR of the cap to maintain the feedback
stability margin, and if the ESR was too low, the margin went away and
the circuit would oscillate. There is an old TI app note discussing
this behavior here:

http://www.ti.com/lit/wp/snoa842/snoa842.pdf

I don't know if the Tek board has this problem or not.

Besides the ESR issue, as long as the voltage rating of the new cap
meets or exceeds that of the Ta cap, I can't think of any reason not
to substitute. I do suggest using an NPO cap since it's the best
dielectric with the best temp stability, and no piezoelectric effect.
If you do get oscillations after substituting, consider putting a 1/2
ohm resistor in series with the cap.

Stuart

On Thu, 17 Dec 2015, optotinker@yahoo.com [TekScopes] wrote:

Hi,


On the Tektronix 7904 PSU converter board, there are two tantalum electrolytic capacitors of 0.1uF. Can I substitute them with ceramic capacitors?


Since the tantalum capacitors are a lot more expensive, the original design must put them there on purpose. What could a 0.1 uF tantalum capacitor do that a 01 uF ceramic capacitor cannot?


Thanks!




[Non-text portions of this message have been removed]



------------------------------------
Posted by: optotinker@yahoo.com
------------------------------------


------------------------------------

Yahoo Groups Links



#yiv9796327001 #yiv9796327001 -- #yiv9796327001ygrp-mkp {border:1px solid #d8d8d8;font-family:Arial;margin:10px 0;padding:0 10px;}#yiv9796327001 #yiv9796327001ygrp-mkp hr {border:1px solid #d8d8d8;}#yiv9796327001 #yiv9796327001ygrp-mkp #yiv9796327001hd {color:#628c2a;font-size:85%;font-weight:700;line-height:122%;margin:10px 0;}#yiv9796327001 #yiv9796327001ygrp-mkp #yiv9796327001ads {margin-bottom:10px;}#yiv9796327001 #yiv9796327001ygrp-mkp .yiv9796327001ad {padding:0 0;}#yiv9796327001 #yiv9796327001ygrp-mkp .yiv9796327001ad p {margin:0;}#yiv9796327001 #yiv9796327001ygrp-mkp .yiv9796327001ad a {color:#0000ff;text-decoration:none;}#yiv9796327001 #yiv9796327001ygrp-sponsor #yiv9796327001ygrp-lc {font-family:Arial;}#yiv9796327001 #yiv9796327001ygrp-sponsor #yiv9796327001ygrp-lc #yiv9796327001hd {margin:10px 0px;font-weight:700;font-size:78%;line-height:122%;}#yiv9796327001 #yiv9796327001ygrp-sponsor #yiv9796327001ygrp-lc .yiv9796327001ad {margin-bottom:10px;padding:0 0;}#yiv9
796327001 #yiv9796327001actions {font-family:Verdana;font-size:11px;padding:10px 0;}#yiv9796327001 #yiv9796327001activity {background-color:#e0ecee;float:left;font-family:Verdana;font-size:10px;padding:10px;}#yiv9796327001 #yiv9796327001activity span {font-weight:700;}#yiv9796327001 #yiv9796327001activity span:first-child {text-transform:uppercase;}#yiv9796327001 #yiv9796327001activity span a {color:#5085b6;text-decoration:none;}#yiv9796327001 #yiv9796327001activity span span {color:#ff7900;}#yiv9796327001 #yiv9796327001activity span .yiv9796327001underline {text-decoration:underline;}#yiv9796327001 .yiv9796327001attach {clear:both;display:table;font-family:Arial;font-size:12px;padding:10px 0;width:400px;}#yiv9796327001 .yiv9796327001attach div a {text-decoration:none;}#yiv9796327001 .yiv9796327001attach img {border:none;padding-right:5px;}#yiv9796327001 .yiv9796327001attach label {display:block;margin-bottom:5px;}#yiv9796327001 .yiv9796327001attach label a {text-decoration:
none;}#yiv9796327001 blockquote {margin:0 0 0 4px;}#yiv9796327001 .yiv9796327001bold {font-family:Arial;font-size:13px;font-weight:700;}#yiv9796327001 .yiv9796327001bold a {text-decoration:none;}#yiv9796327001 dd.yiv9796327001last p a {font-family:Verdana;font-weight:700;}#yiv9796327001 dd.yiv9796327001last p span {margin-right:10px;font-family:Verdana;font-weight:700;}#yiv9796327001 dd.yiv9796327001last p span.yiv9796327001yshortcuts {margin-right:0;}#yiv9796327001 div.yiv9796327001attach-table div div a {text-decoration:none;}#yiv9796327001 div.yiv9796327001attach-table {width:400px;}#yiv9796327001 div.yiv9796327001file-title a, #yiv9796327001 div.yiv9796327001file-title a:active, #yiv9796327001 div.yiv9796327001file-title a:hover, #yiv9796327001 div.yiv9796327001file-title a:visited {text-decoration:none;}#yiv9796327001 div.yiv9796327001photo-title a, #yiv9796327001 div.yiv9796327001photo-title a:active, #yiv9796327001 div.yiv9796327001photo-title a:hover, #yiv9796327001
div.yiv9796327001photo-title a:visited {text-decoration:none;}#yiv9796327001 div#yiv9796327001ygrp-mlmsg #yiv9796327001ygrp-msg p a span.yiv9796327001yshortcuts {font-family:Verdana;font-size:10px;font-weight:normal;}#yiv9796327001 .yiv9796327001green {color:#628c2a;}#yiv9796327001 .yiv9796327001MsoNormal {margin:0 0 0 0;}#yiv9796327001 o {font-size:0;}#yiv9796327001 #yiv9796327001photos div {float:left;width:72px;}#yiv9796327001 #yiv9796327001photos div div {border:1px solid #666666;height:62px;overflow:hidden;width:62px;}#yiv9796327001 #yiv9796327001photos div label {color:#666666;font-size:10px;overflow:hidden;text-align:center;white-space:nowrap;width:64px;}#yiv9796327001 #yiv9796327001reco-category {font-size:77%;}#yiv9796327001 #yiv9796327001reco-desc {font-size:77%;}#yiv9796327001 .yiv9796327001replbq {margin:4px;}#yiv9796327001 #yiv9796327001ygrp-actbar div a:first-child {margin-right:2px;padding-right:5px;}#yiv9796327001 #yiv9796327001ygrp-mlmsg {font-size:13px;font
-family:Arial, helvetica, clean, sans-serif;}#yiv9796327001 #yiv9796327001ygrp-mlmsg table {font-size:inherit;font:100%;}#yiv9796327001 #yiv9796327001ygrp-mlmsg select, #yiv9796327001 input, #yiv9796327001 textarea {font:99% Arial, Helvetica, clean, sans-serif;}#yiv9796327001 #yiv9796327001ygrp-mlmsg pre, #yiv9796327001 code {font:115% monospace;}#yiv9796327001 #yiv9796327001ygrp-mlmsg * {line-height:1.22em;}#yiv9796327001 #yiv9796327001ygrp-mlmsg #yiv9796327001logo {padding-bottom:10px;}#yiv9796327001 #yiv9796327001ygrp-msg p a {font-family:Verdana;}#yiv9796327001 #yiv9796327001ygrp-msg p#yiv9796327001attach-count span {color:#1E66AE;font-weight:700;}#yiv9796327001 #yiv9796327001ygrp-reco #yiv9796327001reco-head {color:#ff7900;font-weight:700;}#yiv9796327001 #yiv9796327001ygrp-reco {margin-bottom:20px;padding:0px;}#yiv9796327001 #yiv9796327001ygrp-sponsor #yiv9796327001ov li a {font-size:130%;text-decoration:none;}#yiv9796327001 #yiv9796327001ygrp-sponsor #yiv9796327001ov l
i {font-size:77%;list-style-type:square;padding:6px 0;}#yiv9796327001 #yiv9796327001ygrp-sponsor #yiv9796327001ov ul {margin:0;padding:0 0 0 8px;}#yiv9796327001 #yiv9796327001ygrp-text {font-family:Georgia;}#yiv9796327001 #yiv9796327001ygrp-text p {margin:0 0 1em 0;}#yiv9796327001 #yiv9796327001ygrp-text tt {font-size:120%;}#yiv9796327001 #yiv9796327001ygrp-vital ul li:last-child {border-right:none !important;}#yiv9796327001







------------------------------------
Posted by: machine guy <machineguy59@yahoo.com>
------------------------------------


------------------------------------

Yahoo Groups Links



[Non-text portions of this message have been removed]

#yiv8239107128 #yiv8239107128 -- #yiv8239107128ygrp-mkp {border:1px solid #d8d8d8;font-family:Arial;margin:10px 0;padding:0 10px;}#yiv8239107128 #yiv8239107128ygrp-mkp hr {border:1px solid #d8d8d8;}#yiv8239107128 #yiv8239107128ygrp-mkp #yiv8239107128hd {color:#628c2a;font-size:85%;font-weight:700;line-height:122%;margin:10px 0;}#yiv8239107128 #yiv8239107128ygrp-mkp #yiv8239107128ads {margin-bottom:10px;}#yiv8239107128 #yiv8239107128ygrp-mkp .yiv8239107128ad {padding:0 0;}#yiv8239107128 #yiv8239107128ygrp-mkp .yiv8239107128ad p {margin:0;}#yiv8239107128 #yiv8239107128ygrp-mkp .yiv8239107128ad a {color:#0000ff;text-decoration:none;}#yiv8239107128 #yiv8239107128ygrp-sponsor #yiv8239107128ygrp-lc {font-family:Arial;}#yiv8239107128 #yiv8239107128ygrp-sponsor #yiv8239107128ygrp-lc #yiv8239107128hd {margin:10px 0px;font-weight:700;font-size:78%;line-height:122%;}#yiv8239107128 #yiv8239107128ygrp-sponsor #yiv8239107128ygrp-lc .yiv8239107128ad {margin-bottom:10px;padding:0 0;}#yiv8239107128 #yiv8239107128actions {font-family:Verdana;font-size:11px;padding:10px 0;}#yiv8239107128 #yiv8239107128activity {background-color:#e0ecee;float:left;font-family:Verdana;font-size:10px;padding:10px;}#yiv8239107128 #yiv8239107128activity span {font-weight:700;}#yiv8239107128 #yiv8239107128activity span:first-child {text-transform:uppercase;}#yiv8239107128 #yiv8239107128activity span a {color:#5085b6;text-decoration:none;}#yiv8239107128 #yiv8239107128activity span span {color:#ff7900;}#yiv8239107128 #yiv8239107128activity span .yiv8239107128underline {text-decoration:underline;}#yiv8239107128 .yiv8239107128attach {clear:both;display:table;font-family:Arial;font-size:12px;padding:10px 0;width:400px;}#yiv8239107128 .yiv8239107128attach div a {text-decoration:none;}#yiv8239107128 .yiv8239107128attach img {border:none;padding-right:5px;}#yiv8239107128 .yiv8239107128attach label {display:block;margin-bottom:5px;}#yiv8239107128 .yiv8239107128attach label a {text-decoration:none;}#yiv8239107128 blockquote {margin:0 0 0 4px;}#yiv8239107128 .yiv8239107128bold {font-family:Arial;font-size:13px;font-weight:700;}#yiv8239107128 .yiv8239107128bold a {text-decoration:none;}#yiv8239107128 dd.yiv8239107128last p a {font-family:Verdana;font-weight:700;}#yiv8239107128 dd.yiv8239107128last p span {margin-right:10px;font-family:Verdana;font-weight:700;}#yiv8239107128 dd.yiv8239107128last p span.yiv8239107128yshortcuts {margin-right:0;}#yiv8239107128 div.yiv8239107128attach-table div div a {text-decoration:none;}#yiv8239107128 div.yiv8239107128attach-table {width:400px;}#yiv8239107128 div.yiv8239107128file-title a, #yiv8239107128 div.yiv8239107128file-title a:active, #yiv8239107128 div.yiv8239107128file-title a:hover, #yiv8239107128 div.yiv8239107128file-title a:visited {text-decoration:none;}#yiv8239107128 div.yiv8239107128photo-title a, #yiv8239107128 div.yiv8239107128photo-title a:active, #yiv8239107128 div.yiv8239107128photo-title a:hover, #yiv8239107128 div.yiv8239107128photo-title a:visited {text-decoration:none;}#yiv8239107128 div#yiv8239107128ygrp-mlmsg #yiv8239107128ygrp-msg p a span.yiv8239107128yshortcuts {font-family:Verdana;font-size:10px;font-weight:normal;}#yiv8239107128 .yiv8239107128green {color:#628c2a;}#yiv8239107128 .yiv8239107128MsoNormal {margin:0 0 0 0;}#yiv8239107128 o {font-size:0;}#yiv8239107128 #yiv8239107128photos div {float:left;width:72px;}#yiv8239107128 #yiv8239107128photos div div {border:1px solid #666666;height:62px;overflow:hidden;width:62px;}#yiv8239107128 #yiv8239107128photos div label {color:#666666;font-size:10px;overflow:hidden;text-align:center;white-space:nowrap;width:64px;}#yiv8239107128 #yiv8239107128reco-category {font-size:77%;}#yiv8239107128 #yiv8239107128reco-desc {font-size:77%;}#yiv8239107128 .yiv8239107128replbq {margin:4px;}#yiv8239107128 #yiv8239107128ygrp-actbar div a:first-child {margin-right:2px;padding-right:5px;}#yiv8239107128 #yiv8239107128ygrp-mlmsg {font-size:13px;font-family:Arial, helvetica, clean, sans-serif;}#yiv8239107128 #yiv8239107128ygrp-mlmsg table {font-size:inherit;font:100%;}#yiv8239107128 #yiv8239107128ygrp-mlmsg select, #yiv8239107128 input, #yiv8239107128 textarea {font:99% Arial, Helvetica, clean, sans-serif;}#yiv8239107128 #yiv8239107128ygrp-mlmsg pre, #yiv8239107128 code {font:115% monospace;}#yiv8239107128 #yiv8239107128ygrp-mlmsg * {line-height:1.22em;}#yiv8239107128 #yiv8239107128ygrp-mlmsg #yiv8239107128logo {padding-bottom:10px;}#yiv8239107128 #yiv8239107128ygrp-msg p a {font-family:Verdana;}#yiv8239107128 #yiv8239107128ygrp-msg p#yiv8239107128attach-count span {color:#1E66AE;font-weight:700;}#yiv8239107128 #yiv8239107128ygrp-reco #yiv8239107128reco-head {color:#ff7900;font-weight:700;}#yiv8239107128 #yiv8239107128ygrp-reco {margin-bottom:20px;padding:0px;}#yiv8239107128 #yiv8239107128ygrp-sponsor #yiv8239107128ov li a {font-size:130%;text-decoration:none;}#yiv8239107128 #yiv8239107128ygrp-sponsor #yiv8239107128ov li {font-size:77%;list-style-type:square;padding:6px 0;}#yiv8239107128 #yiv8239107128ygrp-sponsor #yiv8239107128ov ul {margin:0;padding:0 0 0 8px;}#yiv8239107128 #yiv8239107128ygrp-text {font-family:Georgia;}#yiv8239107128 #yiv8239107128ygrp-text p {margin:0 0 1em 0;}#yiv8239107128 #yiv8239107128ygrp-text tt {font-size:120%;}#yiv8239107128 #yiv8239107128ygrp-vital ul li:last-child {border-right:none !important;}#yiv8239107128


Opto Tinker
 

"I try to never use anything other than NPO (or film) caps in a signal"

So can I replace the tantalum capacitors with film capacitors? It is a lot easier for film capacitors to reach around 0.1-0.5 uF. I can't find any NPO ceramic capacitors in local stores, but a lot of film caps.


--------------------------------------------

On Fri, 12/18/15, machine guy machineguy59@yahoo.com [TekScopes] <TekScopes@yahoogroups.com> wrote:

Subject: Re: [TekScopes] Replacing tantalum capacitors with ceramic capacitors
To: "TekScopes@yahoogroups.com" <TekScopes@yahoogroups.com>
Date: Friday, December 18, 2015, 9:26 AM


 











| | This email has been sent from a virus-free computer
protected by Avast.

www.avast.com |



Thanks, I did not know that COG ceramics were stable with
voltage.  Also thanks for the link which shows the change
one can expect from X7R and below.  You have just proven I
don't know everything after all, lol.





From: "Stuart Brorson sdb@cloud9.net [TekScopes]"
<TekScopes@yahoogroups.com>

To: "machine guy machineguy59@yahoo.com
[TekScopes]" <TekScopes@yahoogroups.com>

Sent: Friday, December 18, 2015 7:17 AM

Subject: Re: [TekScopes] Replacing tantalum capacitors with
ceramic capacitors



  Not all ceramic caps are created equal. The voltage
change depends

upon ceramic type. That's why I recommend NPO for this
application --

they change hardly at all (<1%). Here's an example
app note:



http://www.cde.com/resources/catalogs/ceramperf.pdf



Googling around will reveal more info.



I try to never use anything other than NPO (or film) caps in
a signal

path. X7R and below are for decoupling, or non-critical

applications.



Stuart



On Fri, 18 Dec 2015, machine guy machineguy59@yahoo.com
[TekScopes] wrote:



>

> | | This email has been sent from a virus-free computer
protected by Avast.

> www.avast.com |

>

> Take note that ceramic capacitors change value with
voltage. So a de-rate the voltage appropriately.

>

>

> From: "Stuart Brorson sdb@cloud9.net
[TekScopes]" <TekScopes@yahoogroups.com>

> To: "optotinker@yahoo.com [TekScopes]"
<TekScopes@yahoogroups.com>

> Sent: Thursday, December 17, 2015 5:33 PM

> Subject: Re: [TekScopes] Replacing tantalum capacitors
with ceramic capacitors

>

> Some old LDO circuits were unhappy when loaded by
high-quality caps.

> The old circuits relied on the ESR of the cap to
maintain the feedback

> stability margin, and if the ESR was too low, the
margin went away and

> the circuit would oscillate. There is an old TI app
note discussing

> this behavior here:

>

> http://www.ti.com/lit/wp/snoa842/snoa842.pdf

>

> I don't know if the Tek board has this problem or
not.

>

> Besides the ESR issue, as long as the voltage rating of
the new cap

> meets or exceeds that of the Ta cap, I can't think
of any reason not

> to substitute. I do suggest using an NPO cap since
it's the best

> dielectric with the best temp stability, and no
piezoelectric effect.

> If you do get oscillations after substituting, consider
putting a 1/2

> ohm resistor in series with the cap.

>

> Stuart

>

> On Thu, 17 Dec 2015, optotinker@yahoo.com [TekScopes]
wrote:

>

>> Hi,

>>

>>

>> On the Tektronix 7904 PSU converter board, there
are two tantalum electrolytic capacitors of 0.1uF. Can I
substitute them with ceramic capacitors?

>>

>>

>> Since the tantalum capacitors are a lot more
expensive, the original design must put them there on
purpose. What could a 0.1 uF tantalum capacitor do that a 01
uF ceramic capacitor cannot?

>>

>>

>> Thanks!

>>

>>

>>

>>

>> [Non-text portions of this message have been
removed]

>>

>>

>>

>> ------------------------------------

>> Posted by: optotinker@yahoo.com

>> ------------------------------------

>>

>>

>> ------------------------------------

>>

>> Yahoo Groups Links

>>

>>

>>

>>

> #yiv9796327001 #yiv9796327001 -- #yiv9796327001ygrp-mkp
{border:1px solid #d8d8d8;font-family:Arial;margin:10px
0;padding:0 10px;}#yiv9796327001 #yiv9796327001ygrp-mkp hr
{border:1px solid #d8d8d8;}#yiv9796327001
#yiv9796327001ygrp-mkp #yiv9796327001hd
{color:#628c2a;font-size:85%;font-weight:700;line-height:122%;margin:10px
0;}#yiv9796327001 #yiv9796327001ygrp-mkp #yiv9796327001ads
{margin-bottom:10px;}#yiv9796327001 #yiv9796327001ygrp-mkp
.yiv9796327001ad {padding:0 0;}#yiv9796327001
#yiv9796327001ygrp-mkp .yiv9796327001ad p
{margin:0;}#yiv9796327001 #yiv9796327001ygrp-mkp
.yiv9796327001ad a
{color:#0000ff;text-decoration:none;}#yiv9796327001
#yiv9796327001ygrp-sponsor #yiv9796327001ygrp-lc
{font-family:Arial;}#yiv9796327001
#yiv9796327001ygrp-sponsor #yiv9796327001ygrp-lc
#yiv9796327001hd {margin:10px
0px;font-weight:700;font-size:78%;line-height:122%;}#yiv9796327001
#yiv9796327001ygrp-sponsor #yiv9796327001ygrp-lc
.yiv9796327001ad {margin-bottom:10px;padding:0 0;}#yiv9

796327001 #yiv9796327001actions
{font-family:Verdana;font-size:11px;padding:10px
0;}#yiv9796327001 #yiv9796327001activity
{background-color:#e0ecee;float:left;font-family:Verdana;font-size:10px;padding:10px;}#yiv9796327001
#yiv9796327001activity span {font-weight:700;}#yiv9796327001
#yiv9796327001activity span:first-child
{text-transform:uppercase;}#yiv9796327001
#yiv9796327001activity span a
{color:#5085b6;text-decoration:none;}#yiv9796327001
#yiv9796327001activity span span
{color:#ff7900;}#yiv9796327001 #yiv9796327001activity span
.yiv9796327001underline
{text-decoration:underline;}#yiv9796327001
.yiv9796327001attach
{clear:both;display:table;font-family:Arial;font-size:12px;padding:10px
0;width:400px;}#yiv9796327001 .yiv9796327001attach div a
{text-decoration:none;}#yiv9796327001 .yiv9796327001attach
img {border:none;padding-right:5px;}#yiv9796327001
.yiv9796327001attach label
{display:block;margin-bottom:5px;}#yiv9796327001
.yiv9796327001attach label a {text-decoration:

none;}#yiv9796327001 blockquote {margin:0 0 0
4px;}#yiv9796327001 .yiv9796327001bold
{font-family:Arial;font-size:13px;font-weight:700;}#yiv9796327001
.yiv9796327001bold a {text-decoration:none;}#yiv9796327001
dd.yiv9796327001last p a
{font-family:Verdana;font-weight:700;}#yiv9796327001
dd.yiv9796327001last p span
{margin-right:10px;font-family:Verdana;font-weight:700;}#yiv9796327001
dd.yiv9796327001last p span.yiv9796327001yshortcuts
{margin-right:0;}#yiv9796327001
div.yiv9796327001attach-table div div a
{text-decoration:none;}#yiv9796327001
div.yiv9796327001attach-table {width:400px;}#yiv9796327001
div.yiv9796327001file-title a, #yiv9796327001
div.yiv9796327001file-title a:active, #yiv9796327001
div.yiv9796327001file-title a:hover, #yiv9796327001
div.yiv9796327001file-title a:visited
{text-decoration:none;}#yiv9796327001
div.yiv9796327001photo-title a, #yiv9796327001
div.yiv9796327001photo-title a:active, #yiv9796327001
div.yiv9796327001photo-title a:hover, #yiv9796327001

div.yiv9796327001photo-title a:visited
{text-decoration:none;}#yiv9796327001
div#yiv9796327001ygrp-mlmsg #yiv9796327001ygrp-msg p a
span.yiv9796327001yshortcuts
{font-family:Verdana;font-size:10px;font-weight:normal;}#yiv9796327001
.yiv9796327001green {color:#628c2a;}#yiv9796327001
.yiv9796327001MsoNormal {margin:0 0 0 0;}#yiv9796327001 o
{font-size:0;}#yiv9796327001 #yiv9796327001photos div
{float:left;width:72px;}#yiv9796327001 #yiv9796327001photos
div div {border:1px solid
#666666;height:62px;overflow:hidden;width:62px;}#yiv9796327001
#yiv9796327001photos div label
{color:#666666;font-size:10px;overflow:hidden;text-align:center;white-space:nowrap;width:64px;}#yiv9796327001
#yiv9796327001reco-category {font-size:77%;}#yiv9796327001
#yiv9796327001reco-desc {font-size:77%;}#yiv9796327001
.yiv9796327001replbq {margin:4px;}#yiv9796327001
#yiv9796327001ygrp-actbar div a:first-child
{margin-right:2px;padding-right:5px;}#yiv9796327001
#yiv9796327001ygrp-mlmsg {font-size:13px;font

-family:Arial, helvetica, clean, sans-serif;}#yiv9796327001
#yiv9796327001ygrp-mlmsg table
{font-size:inherit;font:100%;}#yiv9796327001
#yiv9796327001ygrp-mlmsg select, #yiv9796327001 input,
#yiv9796327001 textarea {font:99% Arial, Helvetica, clean,
sans-serif;}#yiv9796327001 #yiv9796327001ygrp-mlmsg pre,
#yiv9796327001 code {font:115% monospace;}#yiv9796327001
#yiv9796327001ygrp-mlmsg *
{line-height:1.22em;}#yiv9796327001 #yiv9796327001ygrp-mlmsg
#yiv9796327001logo {padding-bottom:10px;}#yiv9796327001
#yiv9796327001ygrp-msg p a
{font-family:Verdana;}#yiv9796327001 #yiv9796327001ygrp-msg
p#yiv9796327001attach-count span
{color:#1E66AE;font-weight:700;}#yiv9796327001
#yiv9796327001ygrp-reco #yiv9796327001reco-head
{color:#ff7900;font-weight:700;}#yiv9796327001
#yiv9796327001ygrp-reco
{margin-bottom:20px;padding:0px;}#yiv9796327001
#yiv9796327001ygrp-sponsor #yiv9796327001ov li a
{font-size:130%;text-decoration:none;}#yiv9796327001
#yiv9796327001ygrp-sponsor #yiv9796327001ov l

i {font-size:77%;list-style-type:square;padding:6px
0;}#yiv9796327001 #yiv9796327001ygrp-sponsor
#yiv9796327001ov ul {margin:0;padding:0 0 0
8px;}#yiv9796327001 #yiv9796327001ygrp-text
{font-family:Georgia;}#yiv9796327001 #yiv9796327001ygrp-text
p {margin:0 0 1em 0;}#yiv9796327001 #yiv9796327001ygrp-text
tt {font-size:120%;}#yiv9796327001 #yiv9796327001ygrp-vital
ul li:last-child {border-right:none
!important;}#yiv9796327001

>

>

>

> [Non-text portions of this message have been
removed]

>

>

>

> ------------------------------------

> Posted by: machine guy
<machineguy59@yahoo.com>

> ------------------------------------

>

>

> ------------------------------------

>

> Yahoo Groups Links

>

>

>

>







#yiv8239107128 #yiv8239107128 -- #yiv8239107128ygrp-mkp
{border:1px solid #d8d8d8;font-family:Arial;margin:10px
0;padding:0 10px;}#yiv8239107128 #yiv8239107128ygrp-mkp hr
{border:1px solid #d8d8d8;}#yiv8239107128
#yiv8239107128ygrp-mkp #yiv8239107128hd
{color:#628c2a;font-size:85%;font-weight:700;line-height:122%;margin:10px
0;}#yiv8239107128 #yiv8239107128ygrp-mkp #yiv8239107128ads
{margin-bottom:10px;}#yiv8239107128 #yiv8239107128ygrp-mkp
.yiv8239107128ad {padding:0 0;}#yiv8239107128
#yiv8239107128ygrp-mkp .yiv8239107128ad p
{margin:0;}#yiv8239107128 #yiv8239107128ygrp-mkp
.yiv8239107128ad a
{color:#0000ff;text-decoration:none;}#yiv8239107128
#yiv8239107128ygrp-sponsor #yiv8239107128ygrp-lc
{font-family:Arial;}#yiv8239107128
#yiv8239107128ygrp-sponsor #yiv8239107128ygrp-lc
#yiv8239107128hd {margin:10px
0px;font-weight:700;font-size:78%;line-height:122%;}#yiv8239107128
#yiv8239107128ygrp-sponsor #yiv8239107128ygrp-lc
.yiv8239107128ad {margin-bottom:10px;padding:0
0;}#yiv8239107128 #yiv8239107128actions
{font-family:Verdana;font-size:11px;padding:10px
0;}#yiv8239107128 #yiv8239107128activity
{background-color:#e0ecee;float:left;font-family:Verdana;font-size:10px;padding:10px;}#yiv8239107128
#yiv8239107128activity span {font-weight:700;}#yiv8239107128
#yiv8239107128activity span:first-child
{text-transform:uppercase;}#yiv8239107128
#yiv8239107128activity span a
{color:#5085b6;text-decoration:none;}#yiv8239107128
#yiv8239107128activity span span
{color:#ff7900;}#yiv8239107128 #yiv8239107128activity span
.yiv8239107128underline
{text-decoration:underline;}#yiv8239107128
.yiv8239107128attach
{clear:both;display:table;font-family:Arial;font-size:12px;padding:10px
0;width:400px;}#yiv8239107128 .yiv8239107128attach div a
{text-decoration:none;}#yiv8239107128 .yiv8239107128attach
img {border:none;padding-right:5px;}#yiv8239107128
.yiv8239107128attach label
{display:block;margin-bottom:5px;}#yiv8239107128
.yiv8239107128attach label a
{text-decoration:none;}#yiv8239107128 blockquote {margin:0 0
0 4px;}#yiv8239107128 .yiv8239107128bold
{font-family:Arial;font-size:13px;font-weight:700;}#yiv8239107128
.yiv8239107128bold a {text-decoration:none;}#yiv8239107128
dd.yiv8239107128last p a
{font-family:Verdana;font-weight:700;}#yiv8239107128
dd.yiv8239107128last p span
{margin-right:10px;font-family:Verdana;font-weight:700;}#yiv8239107128
dd.yiv8239107128last p span.yiv8239107128yshortcuts
{margin-right:0;}#yiv8239107128
div.yiv8239107128attach-table div div a
{text-decoration:none;}#yiv8239107128
div.yiv8239107128attach-table {width:400px;}#yiv8239107128
div.yiv8239107128file-title a, #yiv8239107128
div.yiv8239107128file-title a:active, #yiv8239107128
div.yiv8239107128file-title a:hover, #yiv8239107128
div.yiv8239107128file-title a:visited
{text-decoration:none;}#yiv8239107128
div.yiv8239107128photo-title a, #yiv8239107128
div.yiv8239107128photo-title a:active, #yiv8239107128
div.yiv8239107128photo-title a:hover, #yiv8239107128
div.yiv8239107128photo-title a:visited
{text-decoration:none;}#yiv8239107128
div#yiv8239107128ygrp-mlmsg #yiv8239107128ygrp-msg p a
span.yiv8239107128yshortcuts
{font-family:Verdana;font-size:10px;font-weight:normal;}#yiv8239107128
.yiv8239107128green {color:#628c2a;}#yiv8239107128
.yiv8239107128MsoNormal {margin:0 0 0 0;}#yiv8239107128 o
{font-size:0;}#yiv8239107128 #yiv8239107128photos div
{float:left;width:72px;}#yiv8239107128 #yiv8239107128photos
div div {border:1px solid
#666666;height:62px;overflow:hidden;width:62px;}#yiv8239107128
#yiv8239107128photos div label
{color:#666666;font-size:10px;overflow:hidden;text-align:center;white-space:nowrap;width:64px;}#yiv8239107128
#yiv8239107128reco-category {font-size:77%;}#yiv8239107128
#yiv8239107128reco-desc {font-size:77%;}#yiv8239107128
.yiv8239107128replbq {margin:4px;}#yiv8239107128
#yiv8239107128ygrp-actbar div a:first-child
{margin-right:2px;padding-right:5px;}#yiv8239107128
#yiv8239107128ygrp-mlmsg {font-size:13px;font-family:Arial,
helvetica, clean, sans-serif;}#yiv8239107128
#yiv8239107128ygrp-mlmsg table
{font-size:inherit;font:100%;}#yiv8239107128
#yiv8239107128ygrp-mlmsg select, #yiv8239107128 input,
#yiv8239107128 textarea {font:99% Arial, Helvetica, clean,
sans-serif;}#yiv8239107128 #yiv8239107128ygrp-mlmsg pre,
#yiv8239107128 code {font:115% monospace;}#yiv8239107128
#yiv8239107128ygrp-mlmsg *
{line-height:1.22em;}#yiv8239107128 #yiv8239107128ygrp-mlmsg
#yiv8239107128logo {padding-bottom:10px;}#yiv8239107128
#yiv8239107128ygrp-msg p a
{font-family:Verdana;}#yiv8239107128 #yiv8239107128ygrp-msg
p#yiv8239107128attach-count span
{color:#1E66AE;font-weight:700;}#yiv8239107128
#yiv8239107128ygrp-reco #yiv8239107128reco-head
{color:#ff7900;font-weight:700;}#yiv8239107128
#yiv8239107128ygrp-reco
{margin-bottom:20px;padding:0px;}#yiv8239107128
#yiv8239107128ygrp-sponsor #yiv8239107128ov li a
{font-size:130%;text-decoration:none;}#yiv8239107128
#yiv8239107128ygrp-sponsor #yiv8239107128ov li
{font-size:77%;list-style-type:square;padding:6px
0;}#yiv8239107128 #yiv8239107128ygrp-sponsor
#yiv8239107128ov ul {margin:0;padding:0 0 0
8px;}#yiv8239107128 #yiv8239107128ygrp-text
{font-family:Georgia;}#yiv8239107128 #yiv8239107128ygrp-text
p {margin:0 0 1em 0;}#yiv8239107128 #yiv8239107128ygrp-text
tt {font-size:120%;}#yiv8239107128 #yiv8239107128ygrp-vital
ul li:last-child {border-right:none
!important;}#yiv8239107128

















#yiv4771644283 #yiv4771644283 --
#yiv4771644283ygrp-mkp {
border:1px solid #d8d8d8;font-family:Arial;margin:10px
0;padding:0 10px;}

#yiv4771644283 #yiv4771644283ygrp-mkp hr {
border:1px solid #d8d8d8;}

#yiv4771644283 #yiv4771644283ygrp-mkp #yiv4771644283hd {
color:#628c2a;font-size:85%;font-weight:700;line-height:122%;margin:10px
0;}

#yiv4771644283 #yiv4771644283ygrp-mkp #yiv4771644283ads {
margin-bottom:10px;}

#yiv4771644283 #yiv4771644283ygrp-mkp .yiv4771644283ad {
padding:0 0;}

#yiv4771644283 #yiv4771644283ygrp-mkp .yiv4771644283ad p {
margin:0;}

#yiv4771644283 #yiv4771644283ygrp-mkp .yiv4771644283ad a {
color:#0000ff;text-decoration:none;}
#yiv4771644283 #yiv4771644283ygrp-sponsor
#yiv4771644283ygrp-lc {
font-family:Arial;}

#yiv4771644283 #yiv4771644283ygrp-sponsor
#yiv4771644283ygrp-lc #yiv4771644283hd {
margin:10px
0px;font-weight:700;font-size:78%;line-height:122%;}

#yiv4771644283 #yiv4771644283ygrp-sponsor
#yiv4771644283ygrp-lc .yiv4771644283ad {
margin-bottom:10px;padding:0 0;}

#yiv4771644283 #yiv4771644283actions {
font-family:Verdana;font-size:11px;padding:10px 0;}

#yiv4771644283 #yiv4771644283activity {
background-color:#e0ecee;float:left;font-family:Verdana;font-size:10px;padding:10px;}

#yiv4771644283 #yiv4771644283activity span {
font-weight:700;}

#yiv4771644283 #yiv4771644283activity span:first-child {
text-transform:uppercase;}

#yiv4771644283 #yiv4771644283activity span a {
color:#5085b6;text-decoration:none;}

#yiv4771644283 #yiv4771644283activity span span {
color:#ff7900;}

#yiv4771644283 #yiv4771644283activity span
.yiv4771644283underline {
text-decoration:underline;}

#yiv4771644283 .yiv4771644283attach {
clear:both;display:table;font-family:Arial;font-size:12px;padding:10px
0;width:400px;}

#yiv4771644283 .yiv4771644283attach div a {
text-decoration:none;}

#yiv4771644283 .yiv4771644283attach img {
border:none;padding-right:5px;}

#yiv4771644283 .yiv4771644283attach label {
display:block;margin-bottom:5px;}

#yiv4771644283 .yiv4771644283attach label a {
text-decoration:none;}

#yiv4771644283 blockquote {
margin:0 0 0 4px;}

#yiv4771644283 .yiv4771644283bold {
font-family:Arial;font-size:13px;font-weight:700;}

#yiv4771644283 .yiv4771644283bold a {
text-decoration:none;}

#yiv4771644283 dd.yiv4771644283last p a {
font-family:Verdana;font-weight:700;}

#yiv4771644283 dd.yiv4771644283last p span {
margin-right:10px;font-family:Verdana;font-weight:700;}

#yiv4771644283 dd.yiv4771644283last p
span.yiv4771644283yshortcuts {
margin-right:0;}

#yiv4771644283 div.yiv4771644283attach-table div div a {
text-decoration:none;}

#yiv4771644283 div.yiv4771644283attach-table {
width:400px;}

#yiv4771644283 div.yiv4771644283file-title a, #yiv4771644283
div.yiv4771644283file-title a:active, #yiv4771644283
div.yiv4771644283file-title a:hover, #yiv4771644283
div.yiv4771644283file-title a:visited {
text-decoration:none;}

#yiv4771644283 div.yiv4771644283photo-title a,
#yiv4771644283 div.yiv4771644283photo-title a:active,
#yiv4771644283 div.yiv4771644283photo-title a:hover,
#yiv4771644283 div.yiv4771644283photo-title a:visited {
text-decoration:none;}

#yiv4771644283 div#yiv4771644283ygrp-mlmsg
#yiv4771644283ygrp-msg p a span.yiv4771644283yshortcuts {
font-family:Verdana;font-size:10px;font-weight:normal;}

#yiv4771644283 .yiv4771644283green {
color:#628c2a;}

#yiv4771644283 .yiv4771644283MsoNormal {
margin:0 0 0 0;}

#yiv4771644283 o {
font-size:0;}

#yiv4771644283 #yiv4771644283photos div {
float:left;width:72px;}

#yiv4771644283 #yiv4771644283photos div div {
border:1px solid
#666666;height:62px;overflow:hidden;width:62px;}

#yiv4771644283 #yiv4771644283photos div label {
color:#666666;font-size:10px;overflow:hidden;text-align:center;white-space:nowrap;width:64px;}

#yiv4771644283 #yiv4771644283reco-category {
font-size:77%;}

#yiv4771644283 #yiv4771644283reco-desc {
font-size:77%;}

#yiv4771644283 .yiv4771644283replbq {
margin:4px;}

#yiv4771644283 #yiv4771644283ygrp-actbar div a:first-child {
margin-right:2px;padding-right:5px;}

#yiv4771644283 #yiv4771644283ygrp-mlmsg {
font-size:13px;font-family:Arial, helvetica, clean,
sans-serif;}

#yiv4771644283 #yiv4771644283ygrp-mlmsg table {
font-size:inherit;font:100%;}

#yiv4771644283 #yiv4771644283ygrp-mlmsg select,
#yiv4771644283 input, #yiv4771644283 textarea {
font:99% Arial, Helvetica, clean, sans-serif;}

#yiv4771644283 #yiv4771644283ygrp-mlmsg pre, #yiv4771644283
code {
font:115% monospace;}

#yiv4771644283 #yiv4771644283ygrp-mlmsg * {
line-height:1.22em;}

#yiv4771644283 #yiv4771644283ygrp-mlmsg #yiv4771644283logo {
padding-bottom:10px;}


#yiv4771644283 #yiv4771644283ygrp-msg p a {
font-family:Verdana;}

#yiv4771644283 #yiv4771644283ygrp-msg
p#yiv4771644283attach-count span {
color:#1E66AE;font-weight:700;}

#yiv4771644283 #yiv4771644283ygrp-reco
#yiv4771644283reco-head {
color:#ff7900;font-weight:700;}

#yiv4771644283 #yiv4771644283ygrp-reco {
margin-bottom:20px;padding:0px;}

#yiv4771644283 #yiv4771644283ygrp-sponsor #yiv4771644283ov
li a {
font-size:130%;text-decoration:none;}

#yiv4771644283 #yiv4771644283ygrp-sponsor #yiv4771644283ov
li {
font-size:77%;list-style-type:square;padding:6px 0;}

#yiv4771644283 #yiv4771644283ygrp-sponsor #yiv4771644283ov
ul {
margin:0;padding:0 0 0 8px;}

#yiv4771644283 #yiv4771644283ygrp-text {
font-family:Georgia;}

#yiv4771644283 #yiv4771644283ygrp-text p {
margin:0 0 1em 0;}

#yiv4771644283 #yiv4771644283ygrp-text tt {
font-size:120%;}

#yiv4771644283 #yiv4771644283ygrp-vital ul li:last-child {
border-right:none !important;
}
#yiv4771644283


 

Which parts are those? C1277 and C1278 which filter the +7.5 and -2
volt supplies to U1275?

The parts list shows that the 0.1uF 50 volt tantalums were later
changed to 2.2uF 20 volt tantalum, 1.0uF 50 volt tantalum, and then
1.0uF 50 volt aluminum.

I do not see any reason that ceramic or film capacitors could not be
used although I would watch out for the temperature coefficient of a
high dielectric constant ceramic capacitor. The voltage coefficient
of capacitance would have an insignificant effect with even a high
dielectric constant 50 volt ceramic capacitor because the voltages are
low.

ESR is controlled by other circuit elements. R1277 is in series with
the shunt regulator at pin 6. Pin 2 goes to the substrate of the IC
and just has to be more negative than any other pin; the voltage there
is set by diodes CR1288 to CR1290. R1287 controls the ESR as seen
from T1235.

Maybe despite those resistors the low ESR of ceramic capacitors caused
a problem and they did not want to add another resistor to pin 2.
Another thing which might possibly have happened, and I am just
throwing this out there, is that the ceramic capacitors which are
piezoelectric became audible. Possibly it was just a cost issue; all
of the similar capacitors in the parts list are class 3 capacitors and
back then, a class 2 (X7R, whatever) 0.1uF 10% capacitor with a lower
voltage and temperature coefficient would have been more expensive
than a tantalum.

Given that Tektronix later changed those capacitors anyway, I would
use a 1uF 50V solid tantalum.

On 17 Dec 2015 15:16:44 -0800, you wrote:

Hi,

On the Tektronix 7904 PSU converter board, there are two tantalum electrolytic capacitors of 0.1uF. Can I substitute them with ceramic capacitors?

Since the tantalum capacitors are a lot more expensive, the original design must put them there on purpose. What could a 0.1 uF tantalum capacitor do that a 01 uF ceramic capacitor cannot?

Thanks!


 

While not the case now and as far as the original selection Tektronix
made, NP0/C0G capacitors of that value back then would have been very
expensive. I would consider anything of X7R and better to be
suitable. The really bad ones are Z5U and similar but of course they
are the least expensive.

On Fri, 18 Dec 2015 08:17:05 -0500 (EST), you wrote:

Not all ceramic caps are created equal. The voltage change depends
upon ceramic type. That's why I recommend NPO for this application --
they change hardly at all (<1%). Here's an example app note:

http://www.cde.com/resources/catalogs/ceramperf.pdf

Googling around will reveal more info.

I try to never use anything other than NPO (or film) caps in a signal
path. X7R and below are for decoupling, or non-critical
applications.

Stuart


 

Large value NP0/C0G ceramic capacitors are still more expensive than
many alternatives.

There is no obvious reason that a film capacitor could not be used
except perhaps because of size. The ESR is controlled by other
circuit elements.

I would go with 1uF 50V solid tantalums which is what Tektronix used
at one point.

On Fri, 18 Dec 2015 18:33:10 +0000 (UTC), you wrote:

"I try to never use anything other than NPO (or film) caps in a signal"

So can I replace the tantalum capacitors with film capacitors? It is a lot easier for film capacitors to reach around 0.1-0.5 uF. I can't find any NPO ceramic capacitors in local stores, but a lot of film caps.


Herbert
 

Hi,

did you ever see 0.1 uF made of NP0/C0G therefore the idea of the
dependeny of capacity on voltage is right !!!

Herbert




Am 18.12.2015 17:26, schrieb machine guy machineguy59@yahoo.com [TekScopes]:

| | This email has been sent from a virus-free computer protected by Avast.
www.avast.com |

Thanks, I did not know that COG ceramics were stable with voltage. Also thanks for the link which shows the change one can expect from X7R and below. You have just proven I don't know everything after all, lol.


From: "Stuart Brorson sdb@cloud9.net [TekScopes]" <TekScopes@yahoogroups.com>
To: "machine guy machineguy59@yahoo.com [TekScopes]" <TekScopes@yahoogroups.com>
Sent: Friday, December 18, 2015 7:17 AM
Subject: Re: [TekScopes] Replacing tantalum capacitors with ceramic capacitors

Not all ceramic caps are created equal. The voltage change depends
upon ceramic type. That's why I recommend NPO for this application --
they change hardly at all (<1%). Here's an example app note:

http://www.cde.com/resources/catalogs/ceramperf.pdf

Googling around will reveal more info.

I try to never use anything other than NPO (or film) caps in a signal
path. X7R and below are for decoupling, or non-critical
applications.

Stuart

On Fri, 18 Dec 2015, machine guy machineguy59@yahoo.com [TekScopes] wrote:


| | This email has been sent from a virus-free computer protected by Avast.
www.avast.com |

Take note that ceramic capacitors change value with voltage. So a de-rate the voltage appropriately.


From: "Stuart Brorson sdb@cloud9.net [TekScopes]" <TekScopes@yahoogroups.com>
To: "optotinker@yahoo.com [TekScopes]" <TekScopes@yahoogroups.com>
Sent: Thursday, December 17, 2015 5:33 PM
Subject: Re: [TekScopes] Replacing tantalum capacitors with ceramic capacitors

Some old LDO circuits were unhappy when loaded by high-quality caps.
The old circuits relied on the ESR of the cap to maintain the feedback
stability margin, and if the ESR was too low, the margin went away and
the circuit would oscillate. There is an old TI app note discussing
this behavior here:

http://www.ti.com/lit/wp/snoa842/snoa842.pdf

I don't know if the Tek board has this problem or not.

Besides the ESR issue, as long as the voltage rating of the new cap
meets or exceeds that of the Ta cap, I can't think of any reason not
to substitute. I do suggest using an NPO cap since it's the best
dielectric with the best temp stability, and no piezoelectric effect.
If you do get oscillations after substituting, consider putting a 1/2
ohm resistor in series with the cap.

Stuart

On Thu, 17 Dec 2015, optotinker@yahoo.com [TekScopes] wrote:

Hi,


On the Tektronix 7904 PSU converter board, there are two tantalum electrolytic capacitors of 0.1uF. Can I substitute them with ceramic capacitors?


Since the tantalum capacitors are a lot more expensive, the original design must put them there on purpose. What could a 0.1 uF tantalum capacitor do that a 01 uF ceramic capacitor cannot?


Thanks!








------------------------------------
Posted by: optotinker@yahoo.com
------------------------------------


------------------------------------

Yahoo Groups Links



#yiv9796327001 #yiv9796327001 -- #yiv9796327001ygrp-mkp {border:1px solid #d8d8d8;font-family:Arial;margin:10px 0;padding:0 10px;}#yiv9796327001 #yiv9796327001ygrp-mkp hr {border:1px solid #d8d8d8;}#yiv9796327001 #yiv9796327001ygrp-mkp #yiv9796327001hd {color:#628c2a;font-size:85%;font-weight:700;line-height:122%;margin:10px 0;}#yiv9796327001 #yiv9796327001ygrp-mkp #yiv9796327001ads {margin-bottom:10px;}#yiv9796327001 #yiv9796327001ygrp-mkp .yiv9796327001ad {padding:0 0;}#yiv9796327001 #yiv9796327001ygrp-mkp .yiv9796327001ad p {margin:0;}#yiv9796327001 #yiv9796327001ygrp-mkp .yiv9796327001ad a {color:#0000ff;text-decoration:none;}#yiv9796327001 #yiv9796327001ygrp-sponsor #yiv9796327001ygrp-lc {font-family:Arial;}#yiv9796327001 #yiv9796327001ygrp-sponsor #yiv9796327001ygrp-lc #yiv9796327001hd {margin:10px 0px;font-weight:700;font-size:78%;line-height:122%;}#yiv9796327001 #yiv9796327001ygrp-sponsor #yiv9796327001ygrp-lc .yiv9796327001ad {margin-bottom:10px;padding:0 0;}#yiv
9
796327001 #yiv9796327001actions {font-family:Verdana;font-size:11px;padding:10px 0;}#yiv9796327001 #yiv9796327001activity {background-color:#e0ecee;float:left;font-family:Verdana;font-size:10px;padding:10px;}#yiv9796327001 #yiv9796327001activity span {font-weight:700;}#yiv9796327001 #yiv9796327001activity span:first-child {text-transform:uppercase;}#yiv9796327001 #yiv9796327001activity span a {color:#5085b6;text-decoration:none;}#yiv9796327001 #yiv9796327001activity span span {color:#ff7900;}#yiv9796327001 #yiv9796327001activity span .yiv9796327001underline {text-decoration:underline;}#yiv9796327001 .yiv9796327001attach {clear:both;display:table;font-family:Arial;font-size:12px;padding:10px 0;width:400px;}#yiv9796327001 .yiv9796327001attach div a {text-decoration:none;}#yiv9796327001 .yiv9796327001attach img {border:none;padding-right:5px;}#yiv9796327001 .yiv9796327001attach label {display:block;margin-bottom:5px;}#yiv9796327001 .yiv9796327001attach label a {text-decorati
on:
none;}#yiv9796327001 blockquote {margin:0 0 0 4px;}#yiv9796327001 .yiv9796327001bold {font-family:Arial;font-size:13px;font-weight:700;}#yiv9796327001 .yiv9796327001bold a {text-decoration:none;}#yiv9796327001 dd.yiv9796327001last p a {font-family:Verdana;font-weight:700;}#yiv9796327001 dd.yiv9796327001last p span {margin-right:10px;font-family:Verdana;font-weight:700;}#yiv9796327001 dd.yiv9796327001last p span.yiv9796327001yshortcuts {margin-right:0;}#yiv9796327001 div.yiv9796327001attach-table div div a {text-decoration:none;}#yiv9796327001 div.yiv9796327001attach-table {width:400px;}#yiv9796327001 div.yiv9796327001file-title a, #yiv9796327001 div.yiv9796327001file-title a:active, #yiv9796327001 div.yiv9796327001file-title a:hover, #yiv9796327001 div.yiv9796327001file-title a:visited {text-decoration:none;}#yiv9796327001 div.yiv9796327001photo-title a, #yiv9796327001 div.yiv9796327001photo-title a:active, #yiv9796327001 div.yiv9796327001photo-title a:hover, #yiv97963270
01
div.yiv9796327001photo-title a:visited {text-decoration:none;}#yiv9796327001 div#yiv9796327001ygrp-mlmsg #yiv9796327001ygrp-msg p a span.yiv9796327001yshortcuts {font-family:Verdana;font-size:10px;font-weight:normal;}#yiv9796327001 .yiv9796327001green {color:#628c2a;}#yiv9796327001 .yiv9796327001MsoNormal {margin:0 0 0 0;}#yiv9796327001 o {font-size:0;}#yiv9796327001 #yiv9796327001photos div {float:left;width:72px;}#yiv9796327001 #yiv9796327001photos div div {border:1px solid #666666;height:62px;overflow:hidden;width:62px;}#yiv9796327001 #yiv9796327001photos div label {color:#666666;font-size:10px;overflow:hidden;text-align:center;white-space:nowrap;width:64px;}#yiv9796327001 #yiv9796327001reco-category {font-size:77%;}#yiv9796327001 #yiv9796327001reco-desc {font-size:77%;}#yiv9796327001 .yiv9796327001replbq {margin:4px;}#yiv9796327001 #yiv9796327001ygrp-actbar div a:first-child {margin-right:2px;padding-right:5px;}#yiv9796327001 #yiv9796327001ygrp-mlmsg {font-size:13px;f
ont
-family:Arial, helvetica, clean, sans-serif;}#yiv9796327001 #yiv9796327001ygrp-mlmsg table {font-size:inherit;font:100%;}#yiv9796327001 #yiv9796327001ygrp-mlmsg select, #yiv9796327001 input, #yiv9796327001 textarea {font:99% Arial, Helvetica, clean, sans-serif;}#yiv9796327001 #yiv9796327001ygrp-mlmsg pre, #yiv9796327001 code {font:115% monospace;}#yiv9796327001 #yiv9796327001ygrp-mlmsg * {line-height:1.22em;}#yiv9796327001 #yiv9796327001ygrp-mlmsg #yiv9796327001logo {padding-bottom:10px;}#yiv9796327001 #yiv9796327001ygrp-msg p a {font-family:Verdana;}#yiv9796327001 #yiv9796327001ygrp-msg p#yiv9796327001attach-count span {color:#1E66AE;font-weight:700;}#yiv9796327001 #yiv9796327001ygrp-reco #yiv9796327001reco-head {color:#ff7900;font-weight:700;}#yiv9796327001 #yiv9796327001ygrp-reco {margin-bottom:20px;padding:0px;}#yiv9796327001 #yiv9796327001ygrp-sponsor #yiv9796327001ov li a {font-size:130%;text-decoration:none;}#yiv9796327001 #yiv9796327001ygrp-sponsor #yiv9796327001o
v l
i {font-size:77%;list-style-type:square;padding:6px 0;}#yiv9796327001 #yiv9796327001ygrp-sponsor #yiv9796327001ov ul {margin:0;padding:0 0 0 8px;}#yiv9796327001 #yiv9796327001ygrp-text {font-family:Georgia;}#yiv9796327001 #yiv9796327001ygrp-text p {margin:0 0 1em 0;}#yiv9796327001 #yiv9796327001ygrp-text tt {font-size:120%;}#yiv9796327001 #yiv9796327001ygrp-vital ul li:last-child {border-right:none !important;}#yiv9796327001







------------------------------------
Posted by: machine guy <machineguy59@yahoo.com>
------------------------------------


------------------------------------

Yahoo Groups Links





#yiv8239107128 #yiv8239107128 -- #yiv8239107128ygrp-mkp {border:1px solid #d8d8d8;font-family:Arial;margin:10px 0;padding:0 10px;}#yiv8239107128 #yiv8239107128ygrp-mkp hr {border:1px solid #d8d8d8;}#yiv8239107128 #yiv8239107128ygrp-mkp #yiv8239107128hd {color:#628c2a;font-size:85%;font-weight:700;line-height:122%;margin:10px 0;}#yiv8239107128 #yiv8239107128ygrp-mkp #yiv8239107128ads {margin-bottom:10px;}#yiv8239107128 #yiv8239107128ygrp-mkp .yiv8239107128ad {padding:0 0;}#yiv8239107128 #yiv8239107128ygrp-mkp .yiv8239107128ad p {margin:0;}#yiv8239107128 #yiv8239107128ygrp-mkp .yiv8239107128ad a {color:#0000ff;text-decoration:none;}#yiv8239107128 #yiv8239107128ygrp-sponsor #yiv8239107128ygrp-lc {font-family:Arial;}#yiv8239107128 #yiv8239107128ygrp-sponsor #yiv8239107128ygrp-lc #yiv8239107128hd {margin:10px 0px;font-weight:700;font-size:78%;line-height:122%;}#yiv8239107128 #yiv8239107128ygrp-sponsor #yiv8239107128ygrp-lc .yiv8239107128ad {margin-bottom:10px;padding:0 0;}#yi
v8239107128 #yiv8239107128actions {font-family:Verdana;font-size:11px;padding:10px 0;}#yiv8239107128 #yiv8239107128activity {background-color:#e0ecee;float:left;font-family:Verdana;font-size:10px;padding:10px;}#yiv8239107128 #yiv8239107128activity span {font-weight:700;}#yiv8239107128 #yiv8239107128activity span:first-child {text-transform:uppercase;}#yiv8239107128 #yiv8239107128activity span a {color:#5085b6;text-decoration:none;}#yiv8239107128 #yiv8239107128activity span span {color:#ff7900;}#yiv8239107128 #yiv8239107128activity span .yiv8239107128underline {text-decoration:underline;}#yiv8239107128 .yiv8239107128attach {clear:both;display:table;font-family:Arial;font-size:12px;padding:10px 0;width:400px;}#yiv8239107128 .yiv8239107128attach div a {text-decoration:none;}#yiv8239107128 .yiv8239107128attach img {border:none;padding-right:5px;}#yiv8239107128 .yiv8239107128attach label {display:block;margin-bottom:5px;}#yiv8239107128 .yiv8239107128attach label a {text-decoration
:none;}#yiv8239107128 blockquote {margin:0 0 0 4px;}#yiv8239107128 .yiv8239107128bold {font-family:Arial;font-size:13px;font-weight:700;}#yiv8239107128 .yiv8239107128bold a {text-decoration:none;}#yiv8239107128 dd.yiv8239107128last p a {font-family:Verdana;font-weight:700;}#yiv8239107128 dd.yiv8239107128last p span {margin-right:10px;font-family:Verdana;font-weight:700;}#yiv8239107128 dd.yiv8239107128last p span.yiv8239107128yshortcuts {margin-right:0;}#yiv8239107128 div.yiv8239107128attach-table div div a {text-decoration:none;}#yiv8239107128 div.yiv8239107128attach-table {width:400px;}#yiv8239107128 div.yiv8239107128file-title a, #yiv8239107128 div.yiv8239107128file-title a:active, #yiv8239107128 div.yiv8239107128file-title a:hover, #yiv8239107128 div.yiv8239107128file-title a:visited {text-decoration:none;}#yiv8239107128 div.yiv8239107128photo-title a, #yiv8239107128 div.yiv8239107128photo-title a:active, #yiv8239107128 div.yiv8239107128photo-title a:hover, #yiv8239107128
div.yiv8239107128photo-title a:visited {text-decoration:none;}#yiv8239107128 div#yiv8239107128ygrp-mlmsg #yiv8239107128ygrp-msg p a span.yiv8239107128yshortcuts {font-family:Verdana;font-size:10px;font-weight:normal;}#yiv8239107128 .yiv8239107128green {color:#628c2a;}#yiv8239107128 .yiv8239107128MsoNormal {margin:0 0 0 0;}#yiv8239107128 o {font-size:0;}#yiv8239107128 #yiv8239107128photos div {float:left;width:72px;}#yiv8239107128 #yiv8239107128photos div div {border:1px solid #666666;height:62px;overflow:hidden;width:62px;}#yiv8239107128 #yiv8239107128photos div label {color:#666666;font-size:10px;overflow:hidden;text-align:center;white-space:nowrap;width:64px;}#yiv8239107128 #yiv8239107128reco-category {font-size:77%;}#yiv8239107128 #yiv8239107128reco-desc {font-size:77%;}#yiv8239107128 .yiv8239107128replbq {margin:4px;}#yiv8239107128 #yiv8239107128ygrp-actbar div a:first-child {margin-right:2px;padding-right:5px;}#yiv8239107128 #yiv8239107128ygrp-mlmsg {font-size:13px;font-
family:Arial, helvetica, clean, sans-serif;}#yiv8239107128 #yiv8239107128ygrp-mlmsg table {font-size:inherit;font:100%;}#yiv8239107128 #yiv8239107128ygrp-mlmsg select, #yiv8239107128 input, #yiv8239107128 textarea {font:99% Arial, Helvetica, clean, sans-serif;}#yiv8239107128 #yiv8239107128ygrp-mlmsg pre, #yiv8239107128 code {font:115% monospace;}#yiv8239107128 #yiv8239107128ygrp-mlmsg * {line-height:1.22em;}#yiv8239107128 #yiv8239107128ygrp-mlmsg #yiv8239107128logo {padding-bottom:10px;}#yiv8239107128 #yiv8239107128ygrp-msg p a {font-family:Verdana;}#yiv8239107128 #yiv8239107128ygrp-msg p#yiv8239107128attach-count span {color:#1E66AE;font-weight:700;}#yiv8239107128 #yiv8239107128ygrp-reco #yiv8239107128reco-head {color:#ff7900;font-weight:700;}#yiv8239107128 #yiv8239107128ygrp-reco {margin-bottom:20px;padding:0px;}#yiv8239107128 #yiv8239107128ygrp-sponsor #yiv8239107128ov li a {font-size:130%;text-decoration:none;}#yiv8239107128 #yiv8239107128ygrp-sponsor #yiv8239107128ov li
{font-size:77%;list-style-type:square;padding:6px 0;}#yiv8239107128 #yiv8239107128ygrp-sponsor #yiv8239107128ov ul {margin:0;padding:0 0 0 8px;}#yiv8239107128 #yiv8239107128ygrp-text {font-family:Georgia;}#yiv8239107128 #yiv8239107128ygrp-text p {margin:0 0 1em 0;}#yiv8239107128 #yiv8239107128ygrp-text tt {font-size:120%;}#yiv8239107128 #yiv8239107128ygrp-vital ul li:last-child {border-right:none !important;}#yiv8239107128






Opto Tinker
 

Yes indeed they are C1277 and C1278. I don't know the list of numbers represents a revision history. Otherwise, a 1uF tantalum should be easy to find. It does look like the designers sweated over these capacitors.

There is also a C1371 0.27 uF 50V.


--------------------------------------------

On Fri, 12/18/15, David davidwhess@gmail.com [TekScopes] <TekScopes@yahoogroups.com> wrote:

Subject: Re: [TekScopes] Replacing tantalum capacitors with ceramic capacitors
To: TekScopes@yahoogroups.com
Date: Friday, December 18, 2015, 10:44 AM


 









Which parts are those? C1277 and C1278 which
filter the +7.5 and -2

volt supplies to U1275?



The parts list shows that the 0.1uF 50 volt tantalums were
later

changed to 2.2uF 20 volt tantalum, 1.0uF 50 volt tantalum,
and then

1.0uF 50 volt aluminum.



I do not see any reason that ceramic or film capacitors
could not be

used although I would watch out for the temperature
coefficient of a

high dielectric constant ceramic capacitor. The voltage
coefficient

of capacitance would have an insignificant effect with even
a high

dielectric constant 50 volt ceramic capacitor because the
voltages are

low.



ESR is controlled by other circuit elements. R1277 is in
series with

the shunt regulator at pin 6. Pin 2 goes to the substrate
of the IC

and just has to be more negative than any other pin; the
voltage there

is set by diodes CR1288 to CR1290. R1287 controls the ESR
as seen

from T1235.



Maybe despite those resistors the low ESR of ceramic
capacitors caused

a problem and they did not want to add another resistor to
pin 2.

Another thing which might possibly have happened, and I am
just

throwing this out there, is that the ceramic capacitors
which are

piezoelectric became audible. Possibly it was just a cost
issue; all

of the similar capacitors in the parts list are class 3
capacitors and

back then, a class 2 (X7R, whatever) 0.1uF 10% capacitor
with a lower

voltage and temperature coefficient would have been more
expensive

than a tantalum.



Given that Tektronix later changed those capacitors anyway,
I would

use a 1uF 50V solid tantalum.



On 17 Dec 2015 15:16:44 -0800, you wrote:



>Hi,

>

>On the Tektronix 7904 PSU converter board, there are two
tantalum electrolytic capacitors of 0.1uF. Can I substitute
them with ceramic capacitors?

>

>Since the tantalum capacitors are a lot more expensive,
the original design must put them there on purpose. What
could a 0.1 uF tantalum capacitor do that a 01 uF ceramic
capacitor cannot?

>

>Thanks!











#yiv0347000179 #yiv0347000179 --
#yiv0347000179ygrp-mkp {
border:1px solid #d8d8d8;font-family:Arial;margin:10px
0;padding:0 10px;}

#yiv0347000179 #yiv0347000179ygrp-mkp hr {
border:1px solid #d8d8d8;}

#yiv0347000179 #yiv0347000179ygrp-mkp #yiv0347000179hd {
color:#628c2a;font-size:85%;font-weight:700;line-height:122%;margin:10px
0;}

#yiv0347000179 #yiv0347000179ygrp-mkp #yiv0347000179ads {
margin-bottom:10px;}

#yiv0347000179 #yiv0347000179ygrp-mkp .yiv0347000179ad {
padding:0 0;}

#yiv0347000179 #yiv0347000179ygrp-mkp .yiv0347000179ad p {
margin:0;}

#yiv0347000179 #yiv0347000179ygrp-mkp .yiv0347000179ad a {
color:#0000ff;text-decoration:none;}
#yiv0347000179 #yiv0347000179ygrp-sponsor
#yiv0347000179ygrp-lc {
font-family:Arial;}

#yiv0347000179 #yiv0347000179ygrp-sponsor
#yiv0347000179ygrp-lc #yiv0347000179hd {
margin:10px
0px;font-weight:700;font-size:78%;line-height:122%;}

#yiv0347000179 #yiv0347000179ygrp-sponsor
#yiv0347000179ygrp-lc .yiv0347000179ad {
margin-bottom:10px;padding:0 0;}

#yiv0347000179 #yiv0347000179actions {
font-family:Verdana;font-size:11px;padding:10px 0;}

#yiv0347000179 #yiv0347000179activity {
background-color:#e0ecee;float:left;font-family:Verdana;font-size:10px;padding:10px;}

#yiv0347000179 #yiv0347000179activity span {
font-weight:700;}

#yiv0347000179 #yiv0347000179activity span:first-child {
text-transform:uppercase;}

#yiv0347000179 #yiv0347000179activity span a {
color:#5085b6;text-decoration:none;}

#yiv0347000179 #yiv0347000179activity span span {
color:#ff7900;}

#yiv0347000179 #yiv0347000179activity span
.yiv0347000179underline {
text-decoration:underline;}

#yiv0347000179 .yiv0347000179attach {
clear:both;display:table;font-family:Arial;font-size:12px;padding:10px
0;width:400px;}

#yiv0347000179 .yiv0347000179attach div a {
text-decoration:none;}

#yiv0347000179 .yiv0347000179attach img {
border:none;padding-right:5px;}

#yiv0347000179 .yiv0347000179attach label {
display:block;margin-bottom:5px;}

#yiv0347000179 .yiv0347000179attach label a {
text-decoration:none;}

#yiv0347000179 blockquote {
margin:0 0 0 4px;}

#yiv0347000179 .yiv0347000179bold {
font-family:Arial;font-size:13px;font-weight:700;}

#yiv0347000179 .yiv0347000179bold a {
text-decoration:none;}

#yiv0347000179 dd.yiv0347000179last p a {
font-family:Verdana;font-weight:700;}

#yiv0347000179 dd.yiv0347000179last p span {
margin-right:10px;font-family:Verdana;font-weight:700;}

#yiv0347000179 dd.yiv0347000179last p
span.yiv0347000179yshortcuts {
margin-right:0;}

#yiv0347000179 div.yiv0347000179attach-table div div a {
text-decoration:none;}

#yiv0347000179 div.yiv0347000179attach-table {
width:400px;}

#yiv0347000179 div.yiv0347000179file-title a, #yiv0347000179
div.yiv0347000179file-title a:active, #yiv0347000179
div.yiv0347000179file-title a:hover, #yiv0347000179
div.yiv0347000179file-title a:visited {
text-decoration:none;}

#yiv0347000179 div.yiv0347000179photo-title a,
#yiv0347000179 div.yiv0347000179photo-title a:active,
#yiv0347000179 div.yiv0347000179photo-title a:hover,
#yiv0347000179 div.yiv0347000179photo-title a:visited {
text-decoration:none;}

#yiv0347000179 div#yiv0347000179ygrp-mlmsg
#yiv0347000179ygrp-msg p a span.yiv0347000179yshortcuts {
font-family:Verdana;font-size:10px;font-weight:normal;}

#yiv0347000179 .yiv0347000179green {
color:#628c2a;}

#yiv0347000179 .yiv0347000179MsoNormal {
margin:0 0 0 0;}

#yiv0347000179 o {
font-size:0;}

#yiv0347000179 #yiv0347000179photos div {
float:left;width:72px;}

#yiv0347000179 #yiv0347000179photos div div {
border:1px solid
#666666;height:62px;overflow:hidden;width:62px;}

#yiv0347000179 #yiv0347000179photos div label {
color:#666666;font-size:10px;overflow:hidden;text-align:center;white-space:nowrap;width:64px;}

#yiv0347000179 #yiv0347000179reco-category {
font-size:77%;}

#yiv0347000179 #yiv0347000179reco-desc {
font-size:77%;}

#yiv0347000179 .yiv0347000179replbq {
margin:4px;}

#yiv0347000179 #yiv0347000179ygrp-actbar div a:first-child {
margin-right:2px;padding-right:5px;}

#yiv0347000179 #yiv0347000179ygrp-mlmsg {
font-size:13px;font-family:Arial, helvetica, clean,
sans-serif;}

#yiv0347000179 #yiv0347000179ygrp-mlmsg table {
font-size:inherit;font:100%;}

#yiv0347000179 #yiv0347000179ygrp-mlmsg select,
#yiv0347000179 input, #yiv0347000179 textarea {
font:99% Arial, Helvetica, clean, sans-serif;}

#yiv0347000179 #yiv0347000179ygrp-mlmsg pre, #yiv0347000179
code {
font:115% monospace;}

#yiv0347000179 #yiv0347000179ygrp-mlmsg * {
line-height:1.22em;}

#yiv0347000179 #yiv0347000179ygrp-mlmsg #yiv0347000179logo {
padding-bottom:10px;}


#yiv0347000179 #yiv0347000179ygrp-msg p a {
font-family:Verdana;}

#yiv0347000179 #yiv0347000179ygrp-msg
p#yiv0347000179attach-count span {
color:#1E66AE;font-weight:700;}

#yiv0347000179 #yiv0347000179ygrp-reco
#yiv0347000179reco-head {
color:#ff7900;font-weight:700;}

#yiv0347000179 #yiv0347000179ygrp-reco {
margin-bottom:20px;padding:0px;}

#yiv0347000179 #yiv0347000179ygrp-sponsor #yiv0347000179ov
li a {
font-size:130%;text-decoration:none;}

#yiv0347000179 #yiv0347000179ygrp-sponsor #yiv0347000179ov
li {
font-size:77%;list-style-type:square;padding:6px 0;}

#yiv0347000179 #yiv0347000179ygrp-sponsor #yiv0347000179ov
ul {
margin:0;padding:0 0 0 8px;}

#yiv0347000179 #yiv0347000179ygrp-text {
font-family:Georgia;}

#yiv0347000179 #yiv0347000179ygrp-text p {
margin:0 0 1em 0;}

#yiv0347000179 #yiv0347000179ygrp-text tt {
font-size:120%;}

#yiv0347000179 #yiv0347000179ygrp-vital ul li:last-child {
border-right:none !important;
}
#yiv0347000179


 

I learnt about the requirement for High-ESR caps in LDO circuits, the practical way.

About 10 years ago, I had just recapped an APC 2000VA UPS, which had required about 60 caps (Panasonic FM Low-ESR), and I was very proud of my work, as I stood back and admired it before switching on.


I switched on the AC, heard the classic oscillation noise, but didn't make it in time to switch off, before I heard the explosion, and the good old smell.


I replaced the destroyed regulator and IC's and the associated circuit caps with Panasonic EB (High-ESR), and all was fine.


Since then, I pay particular attention to these tank circuits when recapping.


Nothing like practical experience to cement theory in place ;-)


Menahem Yachad
Israel


Stuart Brorson <sdb@...>
 

did you ever see 0.1 uF made of NP0/C0G therefore the idea of the
dependeny of capacity on voltage is right !!!

Herbert
Hmmm... A quick DigiKey search for 0.1uF, NPO/COG, 50V gives 5 pages of hits. Here's one:

http://www.digikey.com/product-detail/en/C3216C0G1H104J160AA/445-7694-1-ND/2733766

There are tons of others, both SMT and though-hole, and if you open
the search up to other voltage ratings, you get even more hits.

Capacitor technology continues to advance. Every year or so I see new
SMTcap families arrive with specs which were not previously
available.

Stuart



On Fri, 18 Dec 2015, Measurement measurement@hws-electronic.com [TekScopes] wrote:

Hi,

did you ever see 0.1 uF made of NP0/C0G therefore the idea of the
dependeny of capacity on voltage is right !!!

Herbert




Am 18.12.2015 17:26, schrieb machine guy machineguy59@yahoo.com [TekScopes]:

| | This email has been sent from a virus-free computer protected by Avast.
www.avast.com |

Thanks, I did not know that COG ceramics were stable with voltage. Also thanks for the link which shows the change one can expect from X7R and below. You have just proven I don't know everything after all, lol.


From: "Stuart Brorson sdb@cloud9.net [TekScopes]" <TekScopes@yahoogroups.com>
To: "machine guy machineguy59@yahoo.com [TekScopes]" <TekScopes@yahoogroups.com>
Sent: Friday, December 18, 2015 7:17 AM
Subject: Re: [TekScopes] Replacing tantalum capacitors with ceramic capacitors

Not all ceramic caps are created equal. The voltage change depends
upon ceramic type. That's why I recommend NPO for this application --
they change hardly at all (<1%). Here's an example app note:

http://www.cde.com/resources/catalogs/ceramperf.pdf

Googling around will reveal more info.

I try to never use anything other than NPO (or film) caps in a signal
path. X7R and below are for decoupling, or non-critical
applications.

Stuart

On Fri, 18 Dec 2015, machine guy machineguy59@yahoo.com [TekScopes] wrote:


| | This email has been sent from a virus-free computer protected by Avast.
www.avast.com |

Take note that ceramic capacitors change value with voltage. So a de-rate the voltage appropriately.


From: "Stuart Brorson sdb@cloud9.net [TekScopes]" <TekScopes@yahoogroups.com>
To: "optotinker@yahoo.com [TekScopes]" <TekScopes@yahoogroups.com>
Sent: Thursday, December 17, 2015 5:33 PM
Subject: Re: [TekScopes] Replacing tantalum capacitors with ceramic capacitors

Some old LDO circuits were unhappy when loaded by high-quality caps.
The old circuits relied on the ESR of the cap to maintain the feedback
stability margin, and if the ESR was too low, the margin went away and
the circuit would oscillate. There is an old TI app note discussing
this behavior here:

http://www.ti.com/lit/wp/snoa842/snoa842.pdf

I don't know if the Tek board has this problem or not.

Besides the ESR issue, as long as the voltage rating of the new cap
meets or exceeds that of the Ta cap, I can't think of any reason not
to substitute. I do suggest using an NPO cap since it's the best
dielectric with the best temp stability, and no piezoelectric effect.
If you do get oscillations after substituting, consider putting a 1/2
ohm resistor in series with the cap.

Stuart

On Thu, 17 Dec 2015, optotinker@yahoo.com [TekScopes] wrote:

Hi,


On the Tektronix 7904 PSU converter board, there are two tantalum electrolytic capacitors of 0.1uF. Can I substitute them with ceramic capacitors?


Since the tantalum capacitors are a lot more expensive, the original design must put them there on purpose. What could a 0.1 uF tantalum capacitor do that a 01 uF ceramic capacitor cannot?


Thanks!







------------------------------------
Posted by: optotinker@yahoo.com
------------------------------------


------------------------------------

Yahoo Groups Links



#yiv9796327001 #yiv9796327001 -- #yiv9796327001ygrp-mkp {border:1px solid #d8d8d8;font-family:Arial;margin:10px 0;padding:0 10px;}#yiv9796327001 #yiv9796327001ygrp-mkp hr {border:1px solid #d8d8d8;}#yiv9796327001 #yiv9796327001ygrp-mkp #yiv9796327001hd {color:#628c2a;font-size:85%;font-weight:700;line-height:122%;margin:10px 0;}#yiv9796327001 #yiv9796327001ygrp-mkp #yiv9796327001ads {margin-bottom:10px;}#yiv9796327001 #yiv9796327001ygrp-mkp .yiv9796327001ad {padding:0 0;}#yiv9796327001 #yiv9796327001ygrp-mkp .yiv9796327001ad p {margin:0;}#yiv9796327001 #yiv9796327001ygrp-mkp .yiv9796327001ad a {color:#0000ff;text-decoration:none;}#yiv9796327001 #yiv9796327001ygrp-sponsor #yiv9796327001ygrp-lc {font-family:Arial;}#yiv9796327001 #yiv9796327001ygrp-sponsor #yiv9796327001ygrp-lc #yiv9796327001hd {margin:10px 0px;font-weight:700;font-size:78%;line-height:122%;}#yiv9796327001 #yiv9796327001ygrp-sponsor #yiv9796327001ygrp-lc .yiv9796327001ad {margin-bottom:10px;padding:0 0;}#yiv
9
796327001 #yiv9796327001actions {font-family:Verdana;font-size:11px;padding:10px 0;}#yiv9796327001 #yiv9796327001activity {background-color:#e0ecee;float:left;font-family:Verdana;font-size:10px;padding:10px;}#yiv9796327001 #yiv9796327001activity span {font-weight:700;}#yiv9796327001 #yiv9796327001activity span:first-child {text-transform:uppercase;}#yiv9796327001 #yiv9796327001activity span a {color:#5085b6;text-decoration:none;}#yiv9796327001 #yiv9796327001activity span span {color:#ff7900;}#yiv9796327001 #yiv9796327001activity span .yiv9796327001underline {text-decoration:underline;}#yiv9796327001 .yiv9796327001attach {clear:both;display:table;font-family:Arial;font-size:12px;padding:10px 0;width:400px;}#yiv9796327001 .yiv9796327001attach div a {text-decoration:none;}#yiv9796327001 .yiv9796327001attach img {border:none;padding-right:5px;}#yiv9796327001 .yiv9796327001attach label {display:block;margin-bottom:5px;}#yiv9796327001 .yiv9796327001attach label a {text-decorati
on:
none;}#yiv9796327001 blockquote {margin:0 0 0 4px;}#yiv9796327001 .yiv9796327001bold {font-family:Arial;font-size:13px;font-weight:700;}#yiv9796327001 .yiv9796327001bold a {text-decoration:none;}#yiv9796327001 dd.yiv9796327001last p a {font-family:Verdana;font-weight:700;}#yiv9796327001 dd.yiv9796327001last p span {margin-right:10px;font-family:Verdana;font-weight:700;}#yiv9796327001 dd.yiv9796327001last p span.yiv9796327001yshortcuts {margin-right:0;}#yiv9796327001 div.yiv9796327001attach-table div div a {text-decoration:none;}#yiv9796327001 div.yiv9796327001attach-table {width:400px;}#yiv9796327001 div.yiv9796327001file-title a, #yiv9796327001 div.yiv9796327001file-title a:active, #yiv9796327001 div.yiv9796327001file-title a:hover, #yiv9796327001 div.yiv9796327001file-title a:visited {text-decoration:none;}#yiv9796327001 div.yiv9796327001photo-title a, #yiv9796327001 div.yiv9796327001photo-title a:active, #yiv9796327001 div.yiv9796327001photo-title a:hover, #yiv97963270
01
div.yiv9796327001photo-title a:visited {text-decoration:none;}#yiv9796327001 div#yiv9796327001ygrp-mlmsg #yiv9796327001ygrp-msg p a span.yiv9796327001yshortcuts {font-family:Verdana;font-size:10px;font-weight:normal;}#yiv9796327001 .yiv9796327001green {color:#628c2a;}#yiv9796327001 .yiv9796327001MsoNormal {margin:0 0 0 0;}#yiv9796327001 o {font-size:0;}#yiv9796327001 #yiv9796327001photos div {float:left;width:72px;}#yiv9796327001 #yiv9796327001photos div div {border:1px solid #666666;height:62px;overflow:hidden;width:62px;}#yiv9796327001 #yiv9796327001photos div label {color:#666666;font-size:10px;overflow:hidden;text-align:center;white-space:nowrap;width:64px;}#yiv9796327001 #yiv9796327001reco-category {font-size:77%;}#yiv9796327001 #yiv9796327001reco-desc {font-size:77%;}#yiv9796327001 .yiv9796327001replbq {margin:4px;}#yiv9796327001 #yiv9796327001ygrp-actbar div a:first-child {margin-right:2px;padding-right:5px;}#yiv9796327001 #yiv9796327001ygrp-mlmsg {font-size:13px;f
ont
-family:Arial, helvetica, clean, sans-serif;}#yiv9796327001 #yiv9796327001ygrp-mlmsg table {font-size:inherit;font:100%;}#yiv9796327001 #yiv9796327001ygrp-mlmsg select, #yiv9796327001 input, #yiv9796327001 textarea {font:99% Arial, Helvetica, clean, sans-serif;}#yiv9796327001 #yiv9796327001ygrp-mlmsg pre, #yiv9796327001 code {font:115% monospace;}#yiv9796327001 #yiv9796327001ygrp-mlmsg * {line-height:1.22em;}#yiv9796327001 #yiv9796327001ygrp-mlmsg #yiv9796327001logo {padding-bottom:10px;}#yiv9796327001 #yiv9796327001ygrp-msg p a {font-family:Verdana;}#yiv9796327001 #yiv9796327001ygrp-msg p#yiv9796327001attach-count span {color:#1E66AE;font-weight:700;}#yiv9796327001 #yiv9796327001ygrp-reco #yiv9796327001reco-head {color:#ff7900;font-weight:700;}#yiv9796327001 #yiv9796327001ygrp-reco {margin-bottom:20px;padding:0px;}#yiv9796327001 #yiv9796327001ygrp-sponsor #yiv9796327001ov li a {font-size:130%;text-decoration:none;}#yiv9796327001 #yiv9796327001ygrp-sponsor #yiv9796327001o
v l
i {font-size:77%;list-style-type:square;padding:6px 0;}#yiv9796327001 #yiv9796327001ygrp-sponsor #yiv9796327001ov ul {margin:0;padding:0 0 0 8px;}#yiv9796327001 #yiv9796327001ygrp-text {font-family:Georgia;}#yiv9796327001 #yiv9796327001ygrp-text p {margin:0 0 1em 0;}#yiv9796327001 #yiv9796327001ygrp-text tt {font-size:120%;}#yiv9796327001 #yiv9796327001ygrp-vital ul li:last-child {border-right:none !important;}#yiv9796327001






------------------------------------
Posted by: machine guy <machineguy59@yahoo.com>
------------------------------------


------------------------------------

Yahoo Groups Links




#yiv8239107128 #yiv8239107128 -- #yiv8239107128ygrp-mkp {border:1px solid #d8d8d8;font-family:Arial;margin:10px 0;padding:0 10px;}#yiv8239107128 #yiv8239107128ygrp-mkp hr {border:1px solid #d8d8d8;}#yiv8239107128 #yiv8239107128ygrp-mkp #yiv8239107128hd {color:#628c2a;font-size:85%;font-weight:700;line-height:122%;margin:10px 0;}#yiv8239107128 #yiv8239107128ygrp-mkp #yiv8239107128ads {margin-bottom:10px;}#yiv8239107128 #yiv8239107128ygrp-mkp .yiv8239107128ad {padding:0 0;}#yiv8239107128 #yiv8239107128ygrp-mkp .yiv8239107128ad p {margin:0;}#yiv8239107128 #yiv8239107128ygrp-mkp .yiv8239107128ad a {color:#0000ff;text-decoration:none;}#yiv8239107128 #yiv8239107128ygrp-sponsor #yiv8239107128ygrp-lc {font-family:Arial;}#yiv8239107128 #yiv8239107128ygrp-sponsor #yiv8239107128ygrp-lc #yiv8239107128hd {margin:10px 0px;font-weight:700;font-size:78%;line-height:122%;}#yiv8239107128 #yiv8239107128ygrp-sponsor #yiv8239107128ygrp-lc .yiv8239107128ad {margin-bottom:10px;padding:0 0;}#yi
v8239107128 #yiv8239107128actions {font-family:Verdana;font-size:11px;padding:10px 0;}#yiv8239107128 #yiv8239107128activity {background-color:#e0ecee;float:left;font-family:Verdana;font-size:10px;padding:10px;}#yiv8239107128 #yiv8239107128activity span {font-weight:700;}#yiv8239107128 #yiv8239107128activity span:first-child {text-transform:uppercase;}#yiv8239107128 #yiv8239107128activity span a {color:#5085b6;text-decoration:none;}#yiv8239107128 #yiv8239107128activity span span {color:#ff7900;}#yiv8239107128 #yiv8239107128activity span .yiv8239107128underline {text-decoration:underline;}#yiv8239107128 .yiv8239107128attach {clear:both;display:table;font-family:Arial;font-size:12px;padding:10px 0;width:400px;}#yiv8239107128 .yiv8239107128attach div a {text-decoration:none;}#yiv8239107128 .yiv8239107128attach img {border:none;padding-right:5px;}#yiv8239107128 .yiv8239107128attach label {display:block;margin-bottom:5px;}#yiv8239107128 .yiv8239107128attach label a {text-decorati
on
:none;}#yiv8239107128 blockquote {margin:0 0 0 4px;}#yiv8239107128 .yiv8239107128bold {font-family:Arial;font-size:13px;font-weight:700;}#yiv8239107128 .yiv8239107128bold a {text-decoration:none;}#yiv8239107128 dd.yiv8239107128last p a {font-family:Verdana;font-weight:700;}#yiv8239107128 dd.yiv8239107128last p span {margin-right:10px;font-family:Verdana;font-weight:700;}#yiv8239107128 dd.yiv8239107128last p span.yiv8239107128yshortcuts {margin-right:0;}#yiv8239107128 div.yiv8239107128attach-table div div a {text-decoration:none;}#yiv8239107128 div.yiv8239107128attach-table {width:400px;}#yiv8239107128 div.yiv8239107128file-title a, #yiv8239107128 div.yiv8239107128file-title a:active, #yiv8239107128 div.yiv8239107128file-title a:hover, #yiv8239107128 div.yiv8239107128file-title a:visited {text-decoration:none;}#yiv8239107128 div.yiv8239107128photo-title a, #yiv8239107128 div.yiv8239107128photo-title a:active, #yiv8239107128 div.yiv8239107128photo-title a:hover, #yiv823910712
8
div.yiv8239107128photo-title a:visited {text-decoration:none;}#yiv8239107128 div#yiv8239107128ygrp-mlmsg #yiv8239107128ygrp-msg p a span.yiv8239107128yshortcuts {font-family:Verdana;font-size:10px;font-weight:normal;}#yiv8239107128 .yiv8239107128green {color:#628c2a;}#yiv8239107128 .yiv8239107128MsoNormal {margin:0 0 0 0;}#yiv8239107128 o {font-size:0;}#yiv8239107128 #yiv8239107128photos div {float:left;width:72px;}#yiv8239107128 #yiv8239107128photos div div {border:1px solid #666666;height:62px;overflow:hidden;width:62px;}#yiv8239107128 #yiv8239107128photos div label {color:#666666;font-size:10px;overflow:hidden;text-align:center;white-space:nowrap;width:64px;}#yiv8239107128 #yiv8239107128reco-category {font-size:77%;}#yiv8239107128 #yiv8239107128reco-desc {font-size:77%;}#yiv8239107128 .yiv8239107128replbq {margin:4px;}#yiv8239107128 #yiv8239107128ygrp-actbar div a:first-child {margin-right:2px;padding-right:5px;}#yiv8239107128 #yiv8239107128ygrp-mlmsg {font-size:13px;fon
t-
family:Arial, helvetica, clean, sans-serif;}#yiv8239107128 #yiv8239107128ygrp-mlmsg table {font-size:inherit;font:100%;}#yiv8239107128 #yiv8239107128ygrp-mlmsg select, #yiv8239107128 input, #yiv8239107128 textarea {font:99% Arial, Helvetica, clean, sans-serif;}#yiv8239107128 #yiv8239107128ygrp-mlmsg pre, #yiv8239107128 code {font:115% monospace;}#yiv8239107128 #yiv8239107128ygrp-mlmsg * {line-height:1.22em;}#yiv8239107128 #yiv8239107128ygrp-mlmsg #yiv8239107128logo {padding-bottom:10px;}#yiv8239107128 #yiv8239107128ygrp-msg p a {font-family:Verdana;}#yiv8239107128 #yiv8239107128ygrp-msg p#yiv8239107128attach-count span {color:#1E66AE;font-weight:700;}#yiv8239107128 #yiv8239107128ygrp-reco #yiv8239107128reco-head {color:#ff7900;font-weight:700;}#yiv8239107128 #yiv8239107128ygrp-reco {margin-bottom:20px;padding:0px;}#yiv8239107128 #yiv8239107128ygrp-sponsor #yiv8239107128ov li a {font-size:130%;text-decoration:none;}#yiv8239107128 #yiv8239107128ygrp-sponsor #yiv8239107128ov l
i
{font-size:77%;list-style-type:square;padding:6px 0;}#yiv8239107128 #yiv8239107128ygrp-sponsor #yiv8239107128ov ul {margin:0;padding:0 0 0 8px;}#yiv8239107128 #yiv8239107128ygrp-text {font-family:Georgia;}#yiv8239107128 #yiv8239107128ygrp-text p {margin:0 0 1em 0;}#yiv8239107128 #yiv8239107128ygrp-text tt {font-size:120%;}#yiv8239107128 #yiv8239107128ygrp-vital ul li:last-child {border-right:none !important;}#yiv8239107128






------------------------------------
Posted by: Measurement <measurement@hws-electronic.com>
------------------------------------


------------------------------------

Yahoo Groups Links




Opto Tinker
 

I also had an explosion here. LOL

I changed most of the capacitors on the 7904 power supply but left those 0.1 uF tantalums alone for now. The replacements are of the exact value except for C1360 and C1364. They are the right side of pi bridges for +- 54V power outputs, with 8.2 uF each, so I replaced them with 10 uF electrolytic caps. I thought there shouldn't be a problem.

Did I miss something? Because when I turned on the power, the PSU immediately started ticking. In a minute or so, C1371, the 0.27 uF 50V tantalum capacitor, blew up, squatting juices all over. This capacitor connects the base of the beam current sense transistor Q1373 to +17V. Recall I had a problem with the beam being too bright, it could be part of the problem all along.

I replace it with a film capacitor, because that is all I have locally. This time, the ticking is gone but smoke rises from somewhere around there. That PSU is a real 3D design and the exact source of the smoke is hard to see. With 12 kV around, I don't want to feel around for the temperature. The base of Q1373 is tied to "X-7 multiplier", U1615, part CMX114. What can cause a capacitor between the base of Q1373 and +17V? and what is "X-7 multiplier", (CMX114)?



--------------------------------------------

On Sat, 12/19/15, yachadm@gmail.com [TekScopes] <TekScopes@yahoogroups.com> wrote:

Subject: [TekScopes] Re: Replacing tantalum capacitors with ceramic capacitors
To: TekScopes@yahoogroups.com
Date: Saturday, December 19, 2015, 8:56 AM


 









I learnt about the requirement for High-ESR caps in
LDO circuits, the practical way.



About 10 years ago, I had just recapped an APC 2000VA UPS,
which had required about 60 caps (Panasonic FM Low-ESR), and
I was very proud of my work, as I stood back and admired it
before switching on.





I switched on the AC, heard the classic oscillation noise,
but didn't make it in time to switch off, before I heard
the explosion, and the good old smell.





I replaced the destroyed regulator and IC's and the
associated circuit caps with Panasonic EB (High-ESR), and
all was fine.





Since then, I pay particular attention to these tank
circuits when recapping.





Nothing like practical experience to cement theory in place
;-)





Menahem Yachad

Israel

























#yiv9732823755 #yiv9732823755 --
#yiv9732823755ygrp-mkp {
border:1px solid #d8d8d8;font-family:Arial;margin:10px
0;padding:0 10px;}

#yiv9732823755 #yiv9732823755ygrp-mkp hr {
border:1px solid #d8d8d8;}

#yiv9732823755 #yiv9732823755ygrp-mkp #yiv9732823755hd {
color:#628c2a;font-size:85%;font-weight:700;line-height:122%;margin:10px
0;}

#yiv9732823755 #yiv9732823755ygrp-mkp #yiv9732823755ads {
margin-bottom:10px;}

#yiv9732823755 #yiv9732823755ygrp-mkp .yiv9732823755ad {
padding:0 0;}

#yiv9732823755 #yiv9732823755ygrp-mkp .yiv9732823755ad p {
margin:0;}

#yiv9732823755 #yiv9732823755ygrp-mkp .yiv9732823755ad a {
color:#0000ff;text-decoration:none;}
#yiv9732823755 #yiv9732823755ygrp-sponsor
#yiv9732823755ygrp-lc {
font-family:Arial;}

#yiv9732823755 #yiv9732823755ygrp-sponsor
#yiv9732823755ygrp-lc #yiv9732823755hd {
margin:10px
0px;font-weight:700;font-size:78%;line-height:122%;}

#yiv9732823755 #yiv9732823755ygrp-sponsor
#yiv9732823755ygrp-lc .yiv9732823755ad {
margin-bottom:10px;padding:0 0;}

#yiv9732823755 #yiv9732823755actions {
font-family:Verdana;font-size:11px;padding:10px 0;}

#yiv9732823755 #yiv9732823755activity {
background-color:#e0ecee;float:left;font-family:Verdana;font-size:10px;padding:10px;}

#yiv9732823755 #yiv9732823755activity span {
font-weight:700;}

#yiv9732823755 #yiv9732823755activity span:first-child {
text-transform:uppercase;}

#yiv9732823755 #yiv9732823755activity span a {
color:#5085b6;text-decoration:none;}

#yiv9732823755 #yiv9732823755activity span span {
color:#ff7900;}

#yiv9732823755 #yiv9732823755activity span
.yiv9732823755underline {
text-decoration:underline;}

#yiv9732823755 .yiv9732823755attach {
clear:both;display:table;font-family:Arial;font-size:12px;padding:10px
0;width:400px;}

#yiv9732823755 .yiv9732823755attach div a {
text-decoration:none;}

#yiv9732823755 .yiv9732823755attach img {
border:none;padding-right:5px;}

#yiv9732823755 .yiv9732823755attach label {
display:block;margin-bottom:5px;}

#yiv9732823755 .yiv9732823755attach label a {
text-decoration:none;}

#yiv9732823755 blockquote {
margin:0 0 0 4px;}

#yiv9732823755 .yiv9732823755bold {
font-family:Arial;font-size:13px;font-weight:700;}

#yiv9732823755 .yiv9732823755bold a {
text-decoration:none;}

#yiv9732823755 dd.yiv9732823755last p a {
font-family:Verdana;font-weight:700;}

#yiv9732823755 dd.yiv9732823755last p span {
margin-right:10px;font-family:Verdana;font-weight:700;}

#yiv9732823755 dd.yiv9732823755last p
span.yiv9732823755yshortcuts {
margin-right:0;}

#yiv9732823755 div.yiv9732823755attach-table div div a {
text-decoration:none;}

#yiv9732823755 div.yiv9732823755attach-table {
width:400px;}

#yiv9732823755 div.yiv9732823755file-title a, #yiv9732823755
div.yiv9732823755file-title a:active, #yiv9732823755
div.yiv9732823755file-title a:hover, #yiv9732823755
div.yiv9732823755file-title a:visited {
text-decoration:none;}

#yiv9732823755 div.yiv9732823755photo-title a,
#yiv9732823755 div.yiv9732823755photo-title a:active,
#yiv9732823755 div.yiv9732823755photo-title a:hover,
#yiv9732823755 div.yiv9732823755photo-title a:visited {
text-decoration:none;}

#yiv9732823755 div#yiv9732823755ygrp-mlmsg
#yiv9732823755ygrp-msg p a span.yiv9732823755yshortcuts {
font-family:Verdana;font-size:10px;font-weight:normal;}

#yiv9732823755 .yiv9732823755green {
color:#628c2a;}

#yiv9732823755 .yiv9732823755MsoNormal {
margin:0 0 0 0;}

#yiv9732823755 o {
font-size:0;}

#yiv9732823755 #yiv9732823755photos div {
float:left;width:72px;}

#yiv9732823755 #yiv9732823755photos div div {
border:1px solid
#666666;height:62px;overflow:hidden;width:62px;}

#yiv9732823755 #yiv9732823755photos div label {
color:#666666;font-size:10px;overflow:hidden;text-align:center;white-space:nowrap;width:64px;}

#yiv9732823755 #yiv9732823755reco-category {
font-size:77%;}

#yiv9732823755 #yiv9732823755reco-desc {
font-size:77%;}

#yiv9732823755 .yiv9732823755replbq {
margin:4px;}

#yiv9732823755 #yiv9732823755ygrp-actbar div a:first-child {
margin-right:2px;padding-right:5px;}

#yiv9732823755 #yiv9732823755ygrp-mlmsg {
font-size:13px;font-family:Arial, helvetica, clean,
sans-serif;}

#yiv9732823755 #yiv9732823755ygrp-mlmsg table {
font-size:inherit;font:100%;}

#yiv9732823755 #yiv9732823755ygrp-mlmsg select,
#yiv9732823755 input, #yiv9732823755 textarea {
font:99% Arial, Helvetica, clean, sans-serif;}

#yiv9732823755 #yiv9732823755ygrp-mlmsg pre, #yiv9732823755
code {
font:115% monospace;}

#yiv9732823755 #yiv9732823755ygrp-mlmsg * {
line-height:1.22em;}

#yiv9732823755 #yiv9732823755ygrp-mlmsg #yiv9732823755logo {
padding-bottom:10px;}


#yiv9732823755 #yiv9732823755ygrp-msg p a {
font-family:Verdana;}

#yiv9732823755 #yiv9732823755ygrp-msg
p#yiv9732823755attach-count span {
color:#1E66AE;font-weight:700;}

#yiv9732823755 #yiv9732823755ygrp-reco
#yiv9732823755reco-head {
color:#ff7900;font-weight:700;}

#yiv9732823755 #yiv9732823755ygrp-reco {
margin-bottom:20px;padding:0px;}

#yiv9732823755 #yiv9732823755ygrp-sponsor #yiv9732823755ov
li a {
font-size:130%;text-decoration:none;}

#yiv9732823755 #yiv9732823755ygrp-sponsor #yiv9732823755ov
li {
font-size:77%;list-style-type:square;padding:6px 0;}

#yiv9732823755 #yiv9732823755ygrp-sponsor #yiv9732823755ov
ul {
margin:0;padding:0 0 0 8px;}

#yiv9732823755 #yiv9732823755ygrp-text {
font-family:Georgia;}

#yiv9732823755 #yiv9732823755ygrp-text p {
margin:0 0 1em 0;}

#yiv9732823755 #yiv9732823755ygrp-text tt {
font-size:120%;}

#yiv9732823755 #yiv9732823755ygrp-vital ul li:last-child {
border-right:none !important;
}
#yiv9732823755


Göran Krusell
 

Hi,

your replacements should be okey. The multiplier creates +21 kV to the CRT
anode. My guess is that the (bad) multiplier itself caused the capacitor
C1371 to blow up. Then you replaced it with a NON-polarized cap and this
worked ok.

When it comes to the smoke you can check resistor R1603 1k5 on board A14. I
think this resistor is cooked because there is a problem with the
multiplier U1615. I hate to give you this advice since it is difficult to
reach R1603 and repair it. Most cables here are very brittle.


Good luck
Göran


Opto Tinker
 

Hi Göran,

Thank you for the suggestion. I lifted the low voltage regulator board and find R1603. On board, it measures 1.5k, and no visible burns.

The construction of the PSU is amazing. They got resistors poking through shielding walls through holes. LOL.


--------------------------------------------

On Sat, 12/19/15, Göran Krusell mc1648pp@gmail.com [TekScopes] <TekScopes@yahoogroups.com> wrote:

Subject: Re: [TekScopes] Re: Replacing tantalum capacitors with ceramic capacitors
To: TekScopes@yahoogroups.com
Date: Saturday, December 19, 2015, 11:38 AM


 









Hi,



your replacements should be okey. The multiplier creates +21
kV to the CRT

anode. My guess is that the (bad) multiplier itself caused
the capacitor

C1371 to blow up. Then you replaced it with a NON-polarized
cap and this

worked ok.



When it comes to the smoke you can check resistor R1603 1k5
on board A14. I

think this resistor is cooked because there is a problem
with the

multiplier U1615. I hate to give you this advice since it is
difficult to

reach R1603 and repair it. Most cables here are very
brittle.



Good luck

Göran



[Non-text portions of this message have been removed]













#yiv9325729642 #yiv9325729642 --
#yiv9325729642ygrp-mkp {
border:1px solid #d8d8d8;font-family:Arial;margin:10px
0;padding:0 10px;}

#yiv9325729642 #yiv9325729642ygrp-mkp hr {
border:1px solid #d8d8d8;}

#yiv9325729642 #yiv9325729642ygrp-mkp #yiv9325729642hd {
color:#628c2a;font-size:85%;font-weight:700;line-height:122%;margin:10px
0;}

#yiv9325729642 #yiv9325729642ygrp-mkp #yiv9325729642ads {
margin-bottom:10px;}

#yiv9325729642 #yiv9325729642ygrp-mkp .yiv9325729642ad {
padding:0 0;}

#yiv9325729642 #yiv9325729642ygrp-mkp .yiv9325729642ad p {
margin:0;}

#yiv9325729642 #yiv9325729642ygrp-mkp .yiv9325729642ad a {
color:#0000ff;text-decoration:none;}
#yiv9325729642 #yiv9325729642ygrp-sponsor
#yiv9325729642ygrp-lc {
font-family:Arial;}

#yiv9325729642 #yiv9325729642ygrp-sponsor
#yiv9325729642ygrp-lc #yiv9325729642hd {
margin:10px
0px;font-weight:700;font-size:78%;line-height:122%;}

#yiv9325729642 #yiv9325729642ygrp-sponsor
#yiv9325729642ygrp-lc .yiv9325729642ad {
margin-bottom:10px;padding:0 0;}

#yiv9325729642 #yiv9325729642actions {
font-family:Verdana;font-size:11px;padding:10px 0;}

#yiv9325729642 #yiv9325729642activity {
background-color:#e0ecee;float:left;font-family:Verdana;font-size:10px;padding:10px;}

#yiv9325729642 #yiv9325729642activity span {
font-weight:700;}

#yiv9325729642 #yiv9325729642activity span:first-child {
text-transform:uppercase;}

#yiv9325729642 #yiv9325729642activity span a {
color:#5085b6;text-decoration:none;}

#yiv9325729642 #yiv9325729642activity span span {
color:#ff7900;}

#yiv9325729642 #yiv9325729642activity span
.yiv9325729642underline {
text-decoration:underline;}

#yiv9325729642 .yiv9325729642attach {
clear:both;display:table;font-family:Arial;font-size:12px;padding:10px
0;width:400px;}

#yiv9325729642 .yiv9325729642attach div a {
text-decoration:none;}

#yiv9325729642 .yiv9325729642attach img {
border:none;padding-right:5px;}

#yiv9325729642 .yiv9325729642attach label {
display:block;margin-bottom:5px;}

#yiv9325729642 .yiv9325729642attach label a {
text-decoration:none;}

#yiv9325729642 blockquote {
margin:0 0 0 4px;}

#yiv9325729642 .yiv9325729642bold {
font-family:Arial;font-size:13px;font-weight:700;}

#yiv9325729642 .yiv9325729642bold a {
text-decoration:none;}

#yiv9325729642 dd.yiv9325729642last p a {
font-family:Verdana;font-weight:700;}

#yiv9325729642 dd.yiv9325729642last p span {
margin-right:10px;font-family:Verdana;font-weight:700;}

#yiv9325729642 dd.yiv9325729642last p
span.yiv9325729642yshortcuts {
margin-right:0;}

#yiv9325729642 div.yiv9325729642attach-table div div a {
text-decoration:none;}

#yiv9325729642 div.yiv9325729642attach-table {
width:400px;}

#yiv9325729642 div.yiv9325729642file-title a, #yiv9325729642
div.yiv9325729642file-title a:active, #yiv9325729642
div.yiv9325729642file-title a:hover, #yiv9325729642
div.yiv9325729642file-title a:visited {
text-decoration:none;}

#yiv9325729642 div.yiv9325729642photo-title a,
#yiv9325729642 div.yiv9325729642photo-title a:active,
#yiv9325729642 div.yiv9325729642photo-title a:hover,
#yiv9325729642 div.yiv9325729642photo-title a:visited {
text-decoration:none;}

#yiv9325729642 div#yiv9325729642ygrp-mlmsg
#yiv9325729642ygrp-msg p a span.yiv9325729642yshortcuts {
font-family:Verdana;font-size:10px;font-weight:normal;}

#yiv9325729642 .yiv9325729642green {
color:#628c2a;}

#yiv9325729642 .yiv9325729642MsoNormal {
margin:0 0 0 0;}

#yiv9325729642 o {
font-size:0;}

#yiv9325729642 #yiv9325729642photos div {
float:left;width:72px;}

#yiv9325729642 #yiv9325729642photos div div {
border:1px solid
#666666;height:62px;overflow:hidden;width:62px;}

#yiv9325729642 #yiv9325729642photos div label {
color:#666666;font-size:10px;overflow:hidden;text-align:center;white-space:nowrap;width:64px;}

#yiv9325729642 #yiv9325729642reco-category {
font-size:77%;}

#yiv9325729642 #yiv9325729642reco-desc {
font-size:77%;}

#yiv9325729642 .yiv9325729642replbq {
margin:4px;}

#yiv9325729642 #yiv9325729642ygrp-actbar div a:first-child {
margin-right:2px;padding-right:5px;}

#yiv9325729642 #yiv9325729642ygrp-mlmsg {
font-size:13px;font-family:Arial, helvetica, clean,
sans-serif;}

#yiv9325729642 #yiv9325729642ygrp-mlmsg table {
font-size:inherit;font:100%;}

#yiv9325729642 #yiv9325729642ygrp-mlmsg select,
#yiv9325729642 input, #yiv9325729642 textarea {
font:99% Arial, Helvetica, clean, sans-serif;}

#yiv9325729642 #yiv9325729642ygrp-mlmsg pre, #yiv9325729642
code {
font:115% monospace;}

#yiv9325729642 #yiv9325729642ygrp-mlmsg * {
line-height:1.22em;}

#yiv9325729642 #yiv9325729642ygrp-mlmsg #yiv9325729642logo {
padding-bottom:10px;}


#yiv9325729642 #yiv9325729642ygrp-msg p a {
font-family:Verdana;}

#yiv9325729642 #yiv9325729642ygrp-msg
p#yiv9325729642attach-count span {
color:#1E66AE;font-weight:700;}

#yiv9325729642 #yiv9325729642ygrp-reco
#yiv9325729642reco-head {
color:#ff7900;font-weight:700;}

#yiv9325729642 #yiv9325729642ygrp-reco {
margin-bottom:20px;padding:0px;}

#yiv9325729642 #yiv9325729642ygrp-sponsor #yiv9325729642ov
li a {
font-size:130%;text-decoration:none;}

#yiv9325729642 #yiv9325729642ygrp-sponsor #yiv9325729642ov
li {
font-size:77%;list-style-type:square;padding:6px 0;}

#yiv9325729642 #yiv9325729642ygrp-sponsor #yiv9325729642ov
ul {
margin:0;padding:0 0 0 8px;}

#yiv9325729642 #yiv9325729642ygrp-text {
font-family:Georgia;}

#yiv9325729642 #yiv9325729642ygrp-text p {
margin:0 0 1em 0;}

#yiv9325729642 #yiv9325729642ygrp-text tt {
font-size:120%;}

#yiv9325729642 #yiv9325729642ygrp-vital ul li:last-child {
border-right:none !important;
}
#yiv9325729642


Dave Hills
 

Hi,
I too am repairing a 7904 which had a shorted C1217 in the line rectifier circuit. Very interesting method used to mechanically secure it and it's companion, C1216.

With regard to your C1371 failure, a couple of possibilities come to mind.

1) If C1350 & C1353 in the +17v filter were not up to par and replacing them decreased the +17v ripple, thus increasing the +17v DC value which may have over-stressed an already aging C1371, causing it to fail.

2) Same story with the other un-regulated DC supplies that might affect the CRT bias and HV, causing excess CRT beam current and also possibly over-stressing C1371 since it is across both +17v and beam current sense. If feasible, you might want to check the voltage across C1371.

Of course there could be other causes as well, but these first came to mind. I would not think replacing the bulk DC filter caps would otherwise be a problem, but may have shifted some operating points and triggered some otherwise aging or weak parts to fail.

Dave


Opto Tinker
 

Thanks! About that C1371 blow out:

I made a mistake on the polarity of C1350, 100 uF 20V. The correct "+" marking was covered by flux and there are many "+" signs that belong to other capacitors on the other side. Well, that is the excuse anyway, LOL. I discovered that when the capacitor's plastic cover peeled because of heating. That is where the smoke comes from, I hope.

The voltage across C1371 is at 17V now, as it should be. The symptom of beam being too bright predates the capacitor change and did not get any better (or worse) by the capacitor change. Now that the fire danger has passed, I can go back debugging again.


--------------------------------------------

On Sun, 12/20/15, dadhills@mindspring.com [TekScopes] <TekScopes@yahoogroups.com> wrote:

Subject: [TekScopes] Re: Replacing tantalum capacitors with ceramic capacitors
To: TekScopes@yahoogroups.com
Date: Sunday, December 20, 2015, 11:25 AM


 









Hi,

I too am repairing a 7904 which had a shorted C1217 in the
line

rectifier circuit. Very interesting method used to
mechanically secure

it and it's companion, C1216.



With regard to your C1371 failure, a couple of possibilities
come to mind.



1) If C1350 & C1353 in the +17v filter were not up to
par and replacing

them decreased the +17v ripple, thus increasing the +17v DC
value which

may have over-stressed an already aging C1371, causing it to
fail.



2) Same story with the other un-regulated DC supplies that
might affect

the CRT bias and HV, causing excess CRT beam current and
also possibly

over-stressing C1371 since it is across both +17v and beam
current

sense. If feasible, you might want to check the voltage
across C1371.



Of course there could be other causes as well, but these
first came to

mind. I would not think replacing the bulk DC filter caps
would

otherwise be a problem, but may have shifted some operating
points and

triggered some otherwise aging or weak parts to fail.



Dave











#yiv7948999213 #yiv7948999213 --
#yiv7948999213ygrp-mkp {
border:1px solid #d8d8d8;font-family:Arial;margin:10px
0;padding:0 10px;}

#yiv7948999213 #yiv7948999213ygrp-mkp hr {
border:1px solid #d8d8d8;}

#yiv7948999213 #yiv7948999213ygrp-mkp #yiv7948999213hd {
color:#628c2a;font-size:85%;font-weight:700;line-height:122%;margin:10px
0;}

#yiv7948999213 #yiv7948999213ygrp-mkp #yiv7948999213ads {
margin-bottom:10px;}

#yiv7948999213 #yiv7948999213ygrp-mkp .yiv7948999213ad {
padding:0 0;}

#yiv7948999213 #yiv7948999213ygrp-mkp .yiv7948999213ad p {
margin:0;}

#yiv7948999213 #yiv7948999213ygrp-mkp .yiv7948999213ad a {
color:#0000ff;text-decoration:none;}
#yiv7948999213 #yiv7948999213ygrp-sponsor
#yiv7948999213ygrp-lc {
font-family:Arial;}

#yiv7948999213 #yiv7948999213ygrp-sponsor
#yiv7948999213ygrp-lc #yiv7948999213hd {
margin:10px
0px;font-weight:700;font-size:78%;line-height:122%;}

#yiv7948999213 #yiv7948999213ygrp-sponsor
#yiv7948999213ygrp-lc .yiv7948999213ad {
margin-bottom:10px;padding:0 0;}

#yiv7948999213 #yiv7948999213actions {
font-family:Verdana;font-size:11px;padding:10px 0;}

#yiv7948999213 #yiv7948999213activity {
background-color:#e0ecee;float:left;font-family:Verdana;font-size:10px;padding:10px;}

#yiv7948999213 #yiv7948999213activity span {
font-weight:700;}

#yiv7948999213 #yiv7948999213activity span:first-child {
text-transform:uppercase;}

#yiv7948999213 #yiv7948999213activity span a {
color:#5085b6;text-decoration:none;}

#yiv7948999213 #yiv7948999213activity span span {
color:#ff7900;}

#yiv7948999213 #yiv7948999213activity span
.yiv7948999213underline {
text-decoration:underline;}

#yiv7948999213 .yiv7948999213attach {
clear:both;display:table;font-family:Arial;font-size:12px;padding:10px
0;width:400px;}

#yiv7948999213 .yiv7948999213attach div a {
text-decoration:none;}

#yiv7948999213 .yiv7948999213attach img {
border:none;padding-right:5px;}

#yiv7948999213 .yiv7948999213attach label {
display:block;margin-bottom:5px;}

#yiv7948999213 .yiv7948999213attach label a {
text-decoration:none;}

#yiv7948999213 blockquote {
margin:0 0 0 4px;}

#yiv7948999213 .yiv7948999213bold {
font-family:Arial;font-size:13px;font-weight:700;}

#yiv7948999213 .yiv7948999213bold a {
text-decoration:none;}

#yiv7948999213 dd.yiv7948999213last p a {
font-family:Verdana;font-weight:700;}

#yiv7948999213 dd.yiv7948999213last p span {
margin-right:10px;font-family:Verdana;font-weight:700;}

#yiv7948999213 dd.yiv7948999213last p
span.yiv7948999213yshortcuts {
margin-right:0;}

#yiv7948999213 div.yiv7948999213attach-table div div a {
text-decoration:none;}

#yiv7948999213 div.yiv7948999213attach-table {
width:400px;}

#yiv7948999213 div.yiv7948999213file-title a, #yiv7948999213
div.yiv7948999213file-title a:active, #yiv7948999213
div.yiv7948999213file-title a:hover, #yiv7948999213
div.yiv7948999213file-title a:visited {
text-decoration:none;}

#yiv7948999213 div.yiv7948999213photo-title a,
#yiv7948999213 div.yiv7948999213photo-title a:active,
#yiv7948999213 div.yiv7948999213photo-title a:hover,
#yiv7948999213 div.yiv7948999213photo-title a:visited {
text-decoration:none;}

#yiv7948999213 div#yiv7948999213ygrp-mlmsg
#yiv7948999213ygrp-msg p a span.yiv7948999213yshortcuts {
font-family:Verdana;font-size:10px;font-weight:normal;}

#yiv7948999213 .yiv7948999213green {
color:#628c2a;}

#yiv7948999213 .yiv7948999213MsoNormal {
margin:0 0 0 0;}

#yiv7948999213 o {
font-size:0;}

#yiv7948999213 #yiv7948999213photos div {
float:left;width:72px;}

#yiv7948999213 #yiv7948999213photos div div {
border:1px solid
#666666;height:62px;overflow:hidden;width:62px;}

#yiv7948999213 #yiv7948999213photos div label {
color:#666666;font-size:10px;overflow:hidden;text-align:center;white-space:nowrap;width:64px;}

#yiv7948999213 #yiv7948999213reco-category {
font-size:77%;}

#yiv7948999213 #yiv7948999213reco-desc {
font-size:77%;}

#yiv7948999213 .yiv7948999213replbq {
margin:4px;}

#yiv7948999213 #yiv7948999213ygrp-actbar div a:first-child {
margin-right:2px;padding-right:5px;}

#yiv7948999213 #yiv7948999213ygrp-mlmsg {
font-size:13px;font-family:Arial, helvetica, clean,
sans-serif;}

#yiv7948999213 #yiv7948999213ygrp-mlmsg table {
font-size:inherit;font:100%;}

#yiv7948999213 #yiv7948999213ygrp-mlmsg select,
#yiv7948999213 input, #yiv7948999213 textarea {
font:99% Arial, Helvetica, clean, sans-serif;}

#yiv7948999213 #yiv7948999213ygrp-mlmsg pre, #yiv7948999213
code {
font:115% monospace;}

#yiv7948999213 #yiv7948999213ygrp-mlmsg * {
line-height:1.22em;}

#yiv7948999213 #yiv7948999213ygrp-mlmsg #yiv7948999213logo {
padding-bottom:10px;}


#yiv7948999213 #yiv7948999213ygrp-msg p a {
font-family:Verdana;}

#yiv7948999213 #yiv7948999213ygrp-msg
p#yiv7948999213attach-count span {
color:#1E66AE;font-weight:700;}

#yiv7948999213 #yiv7948999213ygrp-reco
#yiv7948999213reco-head {
color:#ff7900;font-weight:700;}

#yiv7948999213 #yiv7948999213ygrp-reco {
margin-bottom:20px;padding:0px;}

#yiv7948999213 #yiv7948999213ygrp-sponsor #yiv7948999213ov
li a {
font-size:130%;text-decoration:none;}

#yiv7948999213 #yiv7948999213ygrp-sponsor #yiv7948999213ov
li {
font-size:77%;list-style-type:square;padding:6px 0;}

#yiv7948999213 #yiv7948999213ygrp-sponsor #yiv7948999213ov
ul {
margin:0;padding:0 0 0 8px;}

#yiv7948999213 #yiv7948999213ygrp-text {
font-family:Georgia;}

#yiv7948999213 #yiv7948999213ygrp-text p {
margin:0 0 1em 0;}

#yiv7948999213 #yiv7948999213ygrp-text tt {
font-size:120%;}

#yiv7948999213 #yiv7948999213ygrp-vital ul li:last-child {
border-right:none !important;
}
#yiv7948999213


 

Low dropout regulator circuits, although not all of them, are a
special case where capacitor ESR is more important.

A standard dropout regulator uses a common collector or drain output
transistor and presents a low output impedance. You can still get one
to oscillate with a low ESR output capacitor especially at light loads
where the output impedance is at its highest but it is difficult and
usually trace resistance is enough to prevent it.

A standard low dropout regulator however uses a common emitter or
source output transistor which presents a medium to high output
impedance so the characteristics of the output capacitor become very
important to the frequency compensation and a low ESR just makes
things more difficult. With these you will often find a range of
capacitance and ESR outside of which the regulator will be unstable.

The exception for low dropout regulators are those where a higher
voltage bias supply is used so the output transistor is actually
common collector or drain. These regulators operate like standard
dropout regulators but have low dropout and higher efficiency than low
dropout regulators. Like a standard dropout regulator, they are
tolerant of output capacitor characteristics and ESR.

On 19 Dec 2015 08:56:40 -0800, you wrote:

I learnt about the requirement for High-ESR caps in LDO circuits, the practical way.

...

Menahem Yachad
Israel


vdonisa
 

TDK makes them in C0G up to .22uF in their reasonably priced FK series, available both from Mouser and Digikey.

---In TekScopes@yahoogroups.com, <davidwhess@...> wrote :

Large value NP0/C0G ceramic capacitors are still more expensive than
many alternatives.