Date   
Re: 2465B power supply - Sprague 290uF/200V big blue caps

vdonisa
 

Agreed. That's why I replaced the Schaffner power inlet in my 2235A with an Epcos one:

https://groups.yahoo.com/neo/groups/TekScopes/photos/albums/446209761 https://groups.yahoo.com/neo/groups/TekScopes/photos/albums/446209761

The problem with the power inlets is aggravated by the fact that most of them do NOT contain a fuse in front of the filtering caps.


---In TekScopes@..., <brad.thompson@...> wrote :

Hello--
There are multiple accounts of failures in paper caps used in certain
brands of AC-line inlet filters. Go with the polypropylene.

73--

Brad AA1IP

calib a 24xx scope

mosaicmerc
 

Hi all:
I am looking at investing inn calib eqpt for th 24x scops.

Does this look reasonable : (still needs a PG506?)
TEKTRONIX TM503 SG504 PROGRAMMABLE LEVELED SINE WAVE GENERATOR Working!free ship http://www.ebay.com/itm/TEKTRONIX-TM503-SG504-PROGRAMMABLE-LEVELED-SINE-WAVE-GENERATOR-Working-free-ship-/131626640251?hash=item1ea58f237b

http://www.ebay.com/itm/TEKTRONIX-TM503-SG504-PROGRAMMABLE-LEVELED-SINE-WAVE-GENERATOR-Working-free-ship-/131626640251?hash=item1ea58f237b

TEKTRONIX TM503 SG504 PROGRAMMABLE LEVEL... http://www.ebay.com/itm/TEKTRONIX-TM503-SG504-PROGRAMMABLE-LEVELED-SINE-WAVE-GENERATOR-Working-free-ship-/131626640251?hash=item1ea58f237b US $224.99 Used in Business & Industrial, Electrical & Test Equipment, Test Equipment



View on www.ebay.com http://www.ebay.com/itm/TEKTRONIX-TM503-SG504-PROGRAMMABLE-LEVELED-SINE-WAVE-GENERATOR-Working-free-ship-/131626640251?hash=item1ea58f237b
Preview by Yahoo




Or is this better? can a Pg505 do the job? Still needs a TM503?



Tektronix TM 504 4-compart plug-in mainframe DM 501 FG 501 TG 501 PG 505 FreeS http://www.ebay.com/itm/Tektronix-TM-504-4-compart-plug-in-mainframe-DM-501-FG-501-TG-501-PG-505-FreeS-/272006250070?hash=item3f54d5fe56

http://www.ebay.com/itm/Tektronix-TM-504-4-compart-plug-in-mainframe-DM-501-FG-501-TG-501-PG-505-FreeS-/272006250070?hash=item3f54d5fe56

Tektronix TM 504 4-compart plug-in mainframe DM 501 ... http://www.ebay.com/itm/Tektronix-TM-504-4-compart-plug-in-mainframe-DM-501-FG-501-TG-501-PG-505-FreeS-/272006250070?hash=item3f54d5fe56 US $399.99 Used in Business & Industrial, Electrical & Test Equipment, Test Equipment



View on www.ebay.com http://www.ebay.com/itm/Tektronix-TM-504-4-compart-plug-in-mainframe-DM-501-FG-501-TG-501-PG-505-FreeS-/272006250070?hash=item3f54d5fe56
Preview by Yahoo

Re: Tektronix 453 high voltage problem

Tothwolf
 

On Wed, 14 Oct 2015, David @DWH [TekScopes] wrote:

Back when I researched this issue for the 22xx focus resistors, I found that Tektronix initially used carbon composition resistors from Allen-Bradley and later replaced them with high voltage thin film resistors from Mepco/Centralab. There was evidence that Vishay ended up with these products and they became the VR25 and VR35 series.
In the three 2213 scopes I rebuilt, I found where the switchover from the Allen-Bradley carbon comp to carbon film occurred. I also found that they switched back to a higher grade carbon comp in the even later 2213. I documented what I found in the three scopes in the list archives.

Re: 2465B power supply - Sprague 290uF/200V big blue caps

Tothwolf
 

On Thu, 15 Oct 2015, Tothwolf tothwolf@... [TekScopes] wrote:
On Wed, 14 Oct 2015, vdonisa@... [TekScopes] wrote:

Now I'm debating the X2 and Y2 safety rated caps - paper or polypropylene? Just found a manufacturer (Wima) that does both in proper size and I compared the datasheets. Paper has higher DF (10x more) but can take more dV/dt (10x). Failure rate also slightly in favor of paper. Except that I've seen so many bulged paper ones while plastic seems to be stable. Also measuring old ones, paper seems to increase DF dramatically over time while plastic is more stable.
Polypropylene and polyester. Rifa paper parts will eventually fail again. I can find the part numbers for the ones I'm going to use (and which I used in my other scopes) if you would like them.
A2A1C1016 0.068uF 250V l=18 w=6.5 h=13 [Rifa PME 271 M 568] X2 [paper]
A2A1C1018 0.068uF 250V l=18 w=6.5 h=13 [Rifa PME 271 M 568] X2 [paper]

Epcos/TDK B32922C3683M

A3C1020 2200pF 250V l=12.5 w=3 h=7 [Rifa PME 271 Y 422] [paper]
A3C1051 2200pF 250V l=12.5 w=3 h=7 [Rifa PME 271 Y 422] [paper]

Epcos/TDK B32021A3222M

A3C1052 0.01uF 250V l=18 w=4 h=11 [Rifa PME 289 MB 5100] [paper] (Rifa PME 265 MB)

Epcos/TDK B32022A3103M

Re: TG 501 Time Mark Generator and the Recursive Rathole

Max Frister
 

A couple of hours after I wrote the first note, a 72ls90 arrived in the mail. After some fussing, it appears that you access the back side of the main board by removing the rf board on the other side. Most of the ic's are actually socketed so all I had to do is remove and replace U195.

After this, I have 1 digit! Of course the second digit is not working... I'm guessing U200 is also bad, but it might be a simple contact issue. It seems unlikely that both counters went bad at the same time.

Re: 2465B power supply - Sprague 290uF/200V big blue caps

Tothwolf
 

On Wed, 14 Oct 2015, vdonisa@... [TekScopes] wrote:

Now I'm debating the X2 and Y2 safety rated caps - paper or polypropylene? Just found a manufacturer (Wima) that does both in proper size and I compared the datasheets. Paper has higher DF (10x more) but can take more dV/dt (10x). Failure rate also slightly in favor of paper. Except that I've seen so many bulged paper ones while plastic seems to be stable. Also measuring old ones, paper seems to increase DF dramatically over time while plastic is more stable.
Polypropylene and polyester. Rifa paper parts will eventually fail again. I can find the part numbers for the ones I'm going to use (and which I used in my other scopes) if you would like them.

Re: Tektronix 453 high voltage problem

Joe Laffey
 

On Oct 14, 2015, at 11:09 PM, David @DWH [TekScopes] <TekScopes@...> wrote:.

Failure modes have a lot to do with construction.

Carbon and ceramic composition resistors rely on the bulk properties
of their resistive element which is completely sealed within a solid
envelope. The resistive element itself has high heat capacity.

Thin film resistors have their element deposited on a substrate and
most (all?) use a spiral cut. The substrate provides almost all of
the heat capacity.

This allows carbon composition resistors offer both a higher working
voltage and a higher peak voltage and peak power rating. They also
tend to fail open while thin film resistors tend to fail short.
I found this article with a breakdown of failure modes helpful. No idea where the data came from or how accurate it is.

http://electronicsbus.com/resistor-failure-modes-resistor-reliability-design-guide/

--
Joe Laffey
The Stable
Visual Effects

If anyone is looking for a problem to solve

Joe Laffey
 

If any of you are looking for a problem to solve, and either know about, or want to know about, other scopes. I have a thread on the EEVBlog about an issue with an old Bell & Howell (Heath) scope that has some issues.

http://www.eevblog.com/forum/repair/bell-howell-schools-oscilloscope/

It is an interesting, rather simple, kit scope that, due to its simplicity, is helping me learn more about scope internals as I try to troubleshoot it.

There are pics of my 2465 I am using used for diagnosis...

Thanks,
--
Joe Laffey
The Stable
Visual Effects

Re: 2465B power supply - Sprague 290uF/200V big blue caps

 

On Wed, 14 Oct 2015 23:02:54 -0400, you wrote:



On 10/14/2015 10:35 PM, vdonisa@... [TekScopes] wrote:

<snip>
Now I'm debating the X2 and Y2 safety rated caps - paper or
polypropylene? Just found a manufacturer (Wima) that does both in
proper size and I compared the datasheets. Paper has higher DF (10x
more) but can take more dV/dt (10x). Failure rate also slightly in
favor of paper. Except that I've seen so many bulged paper ones while
plastic seems to be stable. Also measuring old ones, paper seems to
increase DF dramatically over time while plastic is more stable.
Hello--
There are multiple accounts of failures in paper caps used in certain
brands of AC-line inlet filters. Go with the polypropylene.

73--

Brad AA1IP
If there is space, you can also use a higher voltage or grade or both
of safety capacitor. Y2 safety capacitors can replace X2 safety
capacitors for instance (if you can find the higher value) and have a
higher peak voltage rating.

Re: Tektronix 453 high voltage problem

 

On 14 Oct 2015 14:17:45 -0700, you wrote:

David,

Power dissipation was never a problem in these circuits. The
resistors have a voltage rating do to how they are constructed no
matter what their dissipation is.

My point here was simply that there won't be additional degradation caused by heat.
There will not be degradation or derating from heat produced by the
resistor itself anyway. The surrounding environment may be hot and
power dissipation derates as the environmental temperature rises.

I did some googling (actually 'duckduckgoing') to see just what the failure mechanism for overvoltage in a resistor is. By massive overvoltage, it's internal arching. But other than warnings that the resistor will ultimately fail if operated over it's voltage rating, I didn't find why.
Looking for some ratings for the old carbon comp parts Tek used, I found a figure of 500V for half-watt resistors. So, good to go in these circuits.
Failure modes have a lot to do with construction.

Carbon and ceramic composition resistors rely on the bulk properties
of their resistive element which is completely sealed within a solid
envelope. The resistive element itself has high heat capacity.

Thin film resistors have their element deposited on a substrate and
most (all?) use a spiral cut. The substrate provides almost all of
the heat capacity.

This allows carbon composition resistors offer both a higher working
voltage and a higher peak voltage and peak power rating. They also
tend to fail open while thin film resistors tend to fail short.

I do not know how the high voltage thin film resistors I mentioned are
constructed. They have higher voltage ratings than even carbon
composition resistors.

With my naive understanding of high voltage circuits (my background is in digital semiconductors), I figure if it doesn't arc, it's OK. Should I be concerned? In an earlier reply you commented that it would help by simply using more resistors in the string. Doh! I should have thought of that. I'm not keen on going back and replacing these components, but if the potential for failure is just around the corner...
Chances are it will be fine and the risk of damaging the oscilloscope
through further repairs is great enough that I would leave it as it is
now unless there are symptoms of failure.

Back when I researched this issue for the 22xx focus resistors, I
found that Tektronix initially used carbon composition resistors from
Allen-Bradley and later replaced them with high voltage thin film
resistors from Mepco/Centralab. There was evidence that Vishay ended
up with these products and they became the VR25 and VR35 series.

Re: 2465B power supply - Sprague 290uF/200V big blue caps

Dallas Smith
 

Hi Valentin,



The safety caps are in my list also, I used plastic. Your choice for the 290uF replacement looks good, my replacement was 25 x 50mm, didn't fit ideally.


Dallas



---In TekScopes@..., <vdonisa@...> wrote :

You're correct, they don't need any "ultra low Z" replacement, I was just pondering what happened to those series of caps. Guess they were not easy to do right and since polymer probably makes more money too....

I eventually ordered a pair of United Chemicon LXS 330uF/400V in 25/40mm size - these should certainly fit well from a size perspective.

Now I'm debating the X2 and Y2 safety rated caps - paper or polypropylene? Just found a manufacturer (Wima) that does both in proper size and I compared the datasheets. Paper has higher DF (10x more) but can take more dV/dt (10x). Failure rate also slightly in favor of paper. Except that I've seen so many bulged paper ones while plastic seems to be stable. Also measuring old ones, paper seems to increase DF dramatically over time while plastic is more stable.

TAKEN: FTAGH: Tek 7612D Digitizer Manual

Oz-in-DFW
 

This has been spoken for.

Re: 2465B power supply - Sprague 290uF/200V big blue caps

Brad Thompson <brad.thompson@...>
 

On 10/14/2015 10:35 PM, vdonisa@... [TekScopes] wrote:

<snip>
Now I'm debating the X2 and Y2 safety rated caps - paper or polypropylene? Just found a manufacturer (Wima) that does both in proper size and I compared the datasheets. Paper has higher DF (10x more) but can take more dV/dt (10x). Failure rate also slightly in favor of paper. Except that I've seen so many bulged paper ones while plastic seems to be stable. Also measuring old ones, paper seems to increase DF dramatically over time while plastic is more stable.
Hello--
There are multiple accounts of failures in paper caps used in certain brands of AC-line inlet filters. Go with the polypropylene.

73--

Brad AA1IP





---In TekScopes@..., <dosmith54@...> wrote :

Hi again,


I've seen these, very expensive. But you only need low 'Z' at switching frequencies, any general purpose electrolytic cap will work for the 290uF's, but doesn't hurt to put a good low 'Z' one there. I spent a lot of time selecting the caps for my 2467B, the criteria was "in stock" and "long life". I have an Excel sheet with the old parts and replacement if you want it, may save you some time when you update your caps? All from mouser. Of course you may not agree with my selections but they worked ok for me, its still working


Dallas


---In TekScopes@... mailto:TekScopes@..., <vdonisa@...> wrote :

I believe they are now positioning the aluminum-polymer ones as the "ultra low Z" series.







Re: 2465B power supply - Sprague 290uF/200V big blue caps

vdonisa
 

You're correct, they don't need any "ultra low Z" replacement, I was just pondering what happened to those series of caps. Guess they were not easy to do right and since polymer probably makes more money too....

I eventually ordered a pair of United Chemicon LXS 330uF/400V in 25/40mm size - these should certainly fit well from a size perspective.

Now I'm debating the X2 and Y2 safety rated caps - paper or polypropylene? Just found a manufacturer (Wima) that does both in proper size and I compared the datasheets. Paper has higher DF (10x more) but can take more dV/dt (10x). Failure rate also slightly in favor of paper. Except that I've seen so many bulged paper ones while plastic seems to be stable. Also measuring old ones, paper seems to increase DF dramatically over time while plastic is more stable.




---In TekScopes@..., <dosmith54@...> wrote :

Hi again,


I've seen these, very expensive. But you only need low 'Z' at switching frequencies, any general purpose electrolytic cap will work for the 290uF's, but doesn't hurt to put a good low 'Z' one there. I spent a lot of time selecting the caps for my 2467B, the criteria was "in stock" and "long life". I have an Excel sheet with the old parts and replacement if you want it, may save you some time when you update your caps? All from mouser. Of course you may not agree with my selections but they worked ok for me, its still working


Dallas


---In TekScopes@... mailto:TekScopes@..., <vdonisa@...> wrote :

I believe they are now positioning the aluminum-polymer ones as the "ultra low Z" series.

FTAGH: Tek 7612D Digitizer Manual

Oz-in-DFW
 

You pay postage. Cover has a tear, but otherwise good shape. Contact me off list. oz@...

Re: 2465B power supply - Sprague 290uF/200V big blue caps

Dallas Smith
 

Hi again,


I've seen these, very expensive. But you only need low 'Z' at switching frequencies, any general purpose electrolytic cap will work for the 290uF's, but doesn't hurt to put a good low 'Z' one there. I spent a lot of time selecting the caps for my 2467B, the criteria was "in stock" and "long life". I have an Excel sheet with the old parts and replacement if you want it, may save you some time when you update your caps? All from mouser. Of course you may not agree with my selections but they worked ok for me, its still working


Dallas


---In TekScopes@..., <vdonisa@...> wrote :

I believe they are now positioning the aluminum-polymer ones as the "ultra low Z" series.

Re: 2465B power supply - Sprague 290uF/200V big blue caps

vdonisa
 

I believe they are now positioning the aluminum-polymer ones as the "ultra low Z" series.

Re: 2465B power supply - Sprague 290uF/200V big blue caps

Dallas Smith
 

Hi Valentin,

I used 647-UPW2E331MRD from mouser, The caps only see 120Hz ripple, no switching frequency at all. It only has a ripple current of 1.15 amps but is very long life, that is why I chose it.


Dallas


---In TekScopes@..., <vdonisa@...> wrote :

Hi All,

Any idea what ripple current are these caps seeing in normal use?

Thanks!










---In TekScopes@..., <vdonisa@...> wrote :

Hi All,

Any idea what ripple current are these caps seeing in normal use?

Thanks!

Re: 2465B power supply - Sprague 290uF/200V big blue caps

Tothwolf
 

On Wed, 14 Oct 2015, vdonisa@... [TekScopes] wrote:

I've seen GU and GW in a lot of switching power supplies, never found a failed one. Seems rock solid.

As for the "bad caps" fiasco, United wasn't alone :-) If I remember correctly, only Panasonic escaped unscathed at that time.
I'm still replacing faulty capacitors in gear on a weekly basis and still have stacks of SBCs with failed Nippon Chemi-Con KZG/KZJ parts. I've seen failed capacitors even from Panasonic and Rubycon, but mainly in cases where they were improperly specified and/or operated at very high temperatures.

Nichicon had problems with some of the ultra-low ESR HN and HM series parts made in 2001-2004 which was supposedly due to them being overfilled with electrolyte on certain production lines. I still use lots of old stock 2005 and later HN and HM as replacements for faulty Nippon KZG/KZJ and they have been working fine. (All manufacturers discontinued their ultra-low ESR products a few years ago, so the only option now is NOS for the specific applications where ultra-low ESR parts are required.)

Re: 2465B power supply - Sprague 290uF/200V big blue caps

vdonisa
 

I've seen GU and GW in a lot of switching power supplies, never found a failed one. Seems rock solid.

As for the "bad caps" fiasco, United wasn't alone :-) If I remember correctly, only Panasonic escaped unscathed at that time.