Date   
Hints/cautions on replacing caps on 475?

Mark Hatch
 

I have one bad cap on my 475, and while I gain access, I would like to replace all of them. I did some searching on past conversations, and walked away with the following questions:
1) I came across a caution that (paraphrase) "some caps were designed by Tek to connect separated "ground" traces on the board."


There are two ways to interpret this caution:
- The "body" of the cap is used to bridge these traces (!)
- The two of the three leads bridge the traces.


I am 90% sure that second interpretation (the leads form the bridge) is the right interpretation and that the body itself is not providing that bridge. But can someone confirm this?


2) Assuming my interpretation on #1 is correct, then are the two duplicate leads always Negative, Positive, or sometimes one or the other? I know that the duplicate leads are not always negative as C1412 (for example), has the two positive leads attached to the +50 voltage. So the duplicate lead must either be all positive or a mixture...


3) (Finally), has anybody tried re-stuffing the can's? I have done this before on another piece of lab equipment. Just don't know how tightly Tek sealed their caps.


Thanks!


Mark

Re: 468 with no -2450

Samuel Rocha <py1dkw@...>
 

Dear Group,
I had changed the MC1458 and both supplies are now good.
But still no -2450 v!
Regards to ALL,
Sam Rocha






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--------------------------------------------
Em qui, 18/5/17, Samuel Rocha py1dkw@... [TekScopes] <TekScopes@...> escreveu:

Assunto: Re: [TekScopes] 468 with no -2459 v
Para: "David" <@DWH>, "TekScopes@..." <TekScopes@...>
Data: Quinta-feira, 18 de Maio de 2017, 11:50


 









Dear Group,

Sorry, completing the message:



Well, meanwhile I could repair the 55V supply. The VR725
diode, 9,1 v was open, replaced by a 9.1v/1W. This repaired
the +55v, the +15v is ok.Now, the  +5 v  supply is +7.0v
and the -8 v supply is -12v.

I checked the Q401,Q402,Q402, Q617 onboard and Q718 out of
board, they seems to be good with an analog Simpson7
multimeter,

Just for checking the influence of one suplly in tho the
other, I disconnected CR304 in collector of Q402 and
connected it to a +5v supply, still the -8v gives -12v.

I suspect the U506 is faulty. The measures in U506 are:Pin
1= +9,7Pin 2=+17

Pin 3=+5

Pin 4= -12,4Pin 5 =-3,8Pin 6 =0Pin 7 =+2,3Pin8 =+15Is it
possible to remove the  U506 without taking the interface
board out? I think I will have to destroy it cutting all ic
legs and soldering a 8 pin socket.Any ideas about these two
power supplies repair?

many thanks, nice weekend for all And Keep your world blue
as TEKTRONIX !!Sam Rocha 



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Em Quinta-feira, 18 de Maio de 2017 11:40, Samuel Rocha
<py1dkw@...> escreveu:





Dear Group

Well, meanwhile I could repair the 55V supply. The VR725
diode, 9,1 v was open, replaced by a 9.1v/1W. This repaired
the +55v, the +15v is ok.Now, the  +5 v  supply is +7.0v
and the -8 v supply is -12v.

I checked the Q401,Q402,Q402, Q617 onboard and Q718 out of
board, they seems to be good with an analog Simpson7
multimeter,

Just for checking the influence of one suplly in tho the
other, I disconnected CR304 in collector of Q402 and
connected it to a +5v supply, still the -8v gives -12v.

I suspect the U506 is faulty. The measures in U506
are:Pin Pin 

Pin 

 



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Em Terça-feira, 16 de Maio de 2017 3:42, David
<@DWH> escreveu:





On Fri, 12 May 2017 01:30:57 +0000 (UTC), you wrote:





>Dear David ,

>Thank you very much for your attention and answer.

>Confirming the tested voltages:-2450 => zero Volts

>+110 => +110,8 Volts

>-8 did not test

>

>+15v= +15v5v gives 6.75 Volts (higher voltage)



What?  So the +5 volt supply is actually +6.75 volts?  If
so that

needs to be fixed before all else.  A high voltage could
damage the

logic circuits.



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













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Re: 2235 Trigger on one channel

Vince Vielhaber
 

I second dealing with LittleDiode. I bought an obscure Motorola IC from him last year. There were only two sellers left worldwide with any! He shipped fast, and I'm in the US.

Vince.

On 05/18/2017 03:20 PM, Adrian Nicol fenland787a@... [TekScopes] wrote:


Hi Kevin,I've used an ebay seller here in the UK called 'LittleDiode'
for older standard parts and had good service and no problems. They have
some CA3102E's listed at the moment.As to telling fakes - 1960's chips
with nice crisp laser markings ring alarm bells for me!

Regards,Adrian

On Thursday, May 18, 2017 1:46 PM, "KEVIN CLARK maverick.uk@...
[TekScopes]" <TekScopes@...> wrote:


Hi Tom :-)

As Tom indicates I am in the UK. Thank you for the eBay links. How does
one tell
if they are fake?

Cheers

Kevin

Re: Chance to win a Rohde 3Ghz DSA

magnustoelle
 

Thanks - but allow me to add that this is for US and Canadian residents only. To my regrets...

Cheers,

Magnus

On 18/05/2017 22:02, mosaicmerc@... [TekScopes] wrote:

FYI:
http://goemail.microlease.com/ML_RS_FSC3_Spec_An_Raffle http://goemail.microlease.com/ML_RS_FSC3_Spec_An_Raffle

no affiliation. No cost either.

Chance to win a Rohde 3Ghz DSA

mosaicmerc
 

Re: 2235 Trigger on one channel

Adrian Nicol
 

Hi Kevin,I've used an ebay seller here in the UK called 'LittleDiode' for older standard parts and had good service and no problems. They have some CA3102E's listed at the moment.As to telling fakes - 1960's chips with nice crisp laser markings ring alarm bells for me!

Regards,Adrian

On Thursday, May 18, 2017 1:46 PM, "KEVIN CLARK maverick.uk@... [TekScopes]" <TekScopes@...> wrote:


  Hi Tom :-)

As Tom indicates I am in the UK. Thank you for the eBay links. How does one tell
if they are fake?

Cheers

Kevin


On 16 May 2017 at 21:06 "Tom Jobe tomjobe@... [TekScopes]"
<TekScopes@...> wrote:


There are some new CA3102E arrays on eBay.
I believe Kevin is in the UK.
Here's one from Switzerland:

http://www.ebay.com/itm/CA3102E-IC-RCA-2x-5962-01-093-4610-/302278280934?hash=item46613086e6:g:yi0AAOSwnF9Y6mS7
Two of several from the US:

http://www.ebay.com/itm/INTERSIL-HARRIS-CA3102E-DIP-14-Dual-High-Frequency-/361788292835?hash=item543c433ee3:g:lXEAAOSwcLxYDh5H

http://www.ebay.com/itm/CA3102E-Original-New-Harris-Integrated-Circuit-/121052570211?hash=item1c2f4ba263:m:m-2FOnEaLRPmCo6nwF1MBzg
There are many available from China, some of which look like they might
not be fake.

http://www.ebay.com/itm/1PCS-CA3102E-Dual-High-Frequency-Differential-Amplifier-/221115321652?hash=item337b800d34:m:mdO4W1kfigq6oNKBsBWxfMw





On 5/16/2017 9:02 AM, David @DWH [TekScopes] wrote:

On 16 May 2017 14:03:52 +0000, you wrote:

Hi David

Been a little busy so took a while to get back to this. So today
lunch time I started to measure some voltages with my DMM as
suggested, results as follows, something a little amiss (I think?)

U555B Output pin 6 ch1 = 0.139V (0.2V) (0.06V error)
U555B Output pin 6 ch2 = 1.476V (2.5V) (1.02V error)

U310 Output pin 1 ch1 = -3.26V (-3.4V) (0.14V error)
U310 Output pin 1 ch2 = -2.443V (-2.1V) (0.34V error)
You can check the values of R314, R315, R317, R318, and R319 around
U310 but I think the answer is going to be that U310 is bad.

The signal into pin 1/11 is suppose to be low when channel 1 is
selected. When that happens, the output of U555B is disconnected
(pins 1/11 of U310 should not draw any current) and should reach all
the way to ground which is what we are seeing and U310 should be
working but it is not.

When the signal into pin 1/11 is high, channel 2 is selected but pin
1/11 draws more current from U555B. In this case, it is drawing too
much current indicating that either U310 is damaged or R314 and/or
R315 are open.

The fact that U555B is not reaching its full output is irrelevant
because under that condition, U310 should not be forwarding the
trigger signal anyway.

I also looked at the feed from the A3 Board Connection as follows:-

Pin 18 (6.2V) = 6.5V (0.3V error), this also shows (0V) for XY but
can't see how to check this on front panel.
Pin 32 (0.0V) = 0V
Pin 33 (5.0V) = 4.996V
Pin 34 (5.0V) = 4.996V

Some of the values are slightly higher / lower than they should be,
is this the issue?

No, nothing is wrong there.

I wonder if there are any good sources for CA3102 transistor arrays. I
do not see any so if you cannot find one, blast me an email with your
mailing address and I should be able to mail one to you. I will have
to pull it from a junked board but will test it somewhat.



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



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Re: 43 year old 7S14 Dual Trace Dual Timebase Sampling Plugin still works

Ed Breya
 

Yes, I remember the cells I deleted from my first 7S14 were the bigger ones, and smushed in there, with TO-220-sized silastic insulators between and around them. I assume that was the standard factory or field service installation method.

Ed

Re: 43 year old 7S14 Dual Trace Dual Timebase Sampling Plugin still works

 

Hi Ed,
I have no way to know if the cells were original or not in either of my
7S14s. But I did realize that at some point Tek engineers must have decided
the original cells they designed it for were too small. The hole in the PC
board was made for the smaller cells. The larger replacement cells are too
big for the old spaces and require all sorts of "shoe horning" to fit in
their place.

Dennis Tillman W7PF

-----Original Message-----
Sent: Tuesday, May 16, 2017 7:48 PM
Subject: [TekScopes] Re: 43 year old 7S14 Dual Trace Dual Timebase Sampling
Plugin still works

<snip>
I'd guess that the lifetime of the Hg cells depended mostly on the leakage
of the particular sampler diodes installed, and on storage conditions.
Clean, cool, and dry is good. BTW I noticed back when I studied the 7S14
extensively, that somewhere along the line the Hg cell size was changed from
something smaller to something around 225 mAh, as I recall. It could have
been due to part availability issues, but I'm guessing the small ones didn't
last long enough, so were upped significantly in size to cover the diode
leakage and environment conditions. I once did a rough estimate of how long
a 225 mAh cell should last, based on a SWAG of what the diode leakage was at
normal storage temperatures, and came up with about thirty years, as I
recall, so I could picture your numbers being real.

<snip>
Also, do you know for sure that the cells are the original ones?

Ed
------------------------------------
Posted by: edbreya@...
------------------------------------

Re: 2235 Trigger on one channel

Adrian Nicol
 

I'm not sure how you can tell fakes (although laser marked 1960s chips were rare!) but have bought a range of older devices to keep my menagerie of HP & Tek stuff fed and watered from an ebay seller in the UK called 'LittleDiode' with no problems so far. I see they have some CA3102E listed. No affiliation etc.....

Re: Type 503 Oscilloscope Issues

ykochcal
 

"If I have time tomorrow, I'll just temporarily connect the new caps in
place and see what effect that has on the scope's performance and the -100V
bus reading."

That would be a good plan.

The caps of this kind can be shorted, but the tests and the fact that you
get -80V would indicate that they are not shorted or low resistance.

The capacitors can have low uF and/or high ESR, Placing a new caps in
parallel will solve both those problems.

As mentioned if the old caps have high leakage, the connecting just the new
cap will eliminate that issue.

At that point you can determine if the that fixes all the issues.

If there is still other issues I would locate those issues, and then make a
plan to fix all the issues, before "restoring" the caps to reduce the risk
of collateral damage or redoing work to get to other parts.

(I actually, in most cases on a cap like this I just solder the new cap to
the terminals on the bottom of old one and leave the old one in. But that is
just my personal choice)

Thanks for the update

John

Saw this and thought of you!

Dennis McCreery
 

Re: 468 with no -2459 v

 

Are you sure it is not in a socket?

----- Original Message -----
From: Samuel Rocha py1dkw@... [TekScopes]
To: David ; TekScopes@...
Sent: Thursday, May 18, 2017 10:50 AM
Subject: Re: [TekScopes] 468 with no -2459 v



Dear Group,
Sorry, completing the message:

Well, meanwhile I could repair the 55V supply. The VR725 diode, 9,1 v was open, replaced by a 9.1v/1W. This repaired the +55v, the +15v is ok.Now, the +5 v supply is +7.0v and the -8 v supply is -12v.
I checked the Q401,Q402,Q402, Q617 onboard and Q718 out of board, they seems to be good with an analog Simpson7 multimeter,
Just for checking the influence of one suplly in tho the other, I disconnected CR304 in collector of Q402 and connected it to a +5v supply, still the -8v gives -12v.
I suspect the U506 is faulty. The measures in U506 are:Pin 1= +9,7Pin 2=+17
Pin 3=+5
Pin 4= -12,4Pin 5 =-3,8Pin 6 =0Pin 7 =+2,3Pin8 =+15Is it possible to remove the U506 without taking the interface board out? I think I will have to destroy it cutting all ic legs and soldering a 8 pin socket.Any ideas about these two power supplies repair?
many thanks, nice weekend for all And Keep your world blue as TEKTRONIX !!Sam Rocha

Enviado do Yahoo Mail. Baixe o aplicativo

Em Quinta-feira, 18 de Maio de 2017 11:40, Samuel Rocha <py1dkw@...> escreveu:


Dear Group
Well, meanwhile I could repair the 55V supply. The VR725 diode, 9,1 v was open, replaced by a 9.1v/1W. This repaired the +55v, the +15v is ok.Now, the +5 v supply is +7.0v and the -8 v supply is -12v.
I checked the Q401,Q402,Q402, Q617 onboard and Q718 out of board, they seems to be good with an analog Simpson7 multimeter,
Just for checking the influence of one suplly in tho the other, I disconnected CR304 in collector of Q402 and connected it to a +5v supply, still the -8v gives -12v.
I suspect the U506 is faulty. The measures in U506 are:Pin Pin
Pin


Enviado do Yahoo Mail. Baixe o aplicativo

Em Terça-feira, 16 de Maio de 2017 3:42, David <@DWH> escreveu:


On Fri, 12 May 2017 01:30:57 +0000 (UTC), you wrote:

>
>Dear David ,
>Thank you very much for your attention and answer.
>Confirming the tested voltages:-2450 => zero Volts
>+110 => +110,8 Volts
>-8 did not test
>
>+15v= +15v5v gives 6.75 Volts (higher voltage)

What? So the +5 volt supply is actually +6.75 volts? If so that
needs to be fixed before all else. A high voltage could damage the
logic circuits.

Re: 468 with no -2459 v

Samuel Rocha <py1dkw@...>
 

Dear Group,
Sorry, completing the message:


Well, meanwhile I could repair the 55V supply. The VR725 diode, 9,1 v was open, replaced by a 9.1v/1W. This repaired the +55v, the +15v is ok.Now, the  +5 v  supply is +7.0v and the -8 v supply is -12v.
I checked the Q401,Q402,Q402, Q617 onboard and Q718 out of board, they seems to be good with an analog Simpson7 multimeter,
Just for checking the influence of one suplly in tho the other, I disconnected CR304 in collector of Q402 and connected it to a +5v supply, still the -8v gives -12v.
I suspect the U506 is faulty. The measures in U506 are:Pin 1= +9,7Pin 2=+17
Pin 3=+5
Pin 4= -12,4Pin 5 =-3,8Pin 6 =0Pin 7 =+2,3Pin8 =+15Is it possible to remove the  U506 without taking the interface board out? I think I will have to destroy it cutting all ic legs and soldering a 8 pin socket.Any ideas about these two power supplies repair?
many thanks, nice weekend for all And Keep your world blue as TEKTRONIX !!Sam Rocha 


Enviado do Yahoo Mail. Baixe o aplicativo

Em Quinta-feira, 18 de Maio de 2017 11:40, Samuel Rocha <py1dkw@...> escreveu:


Dear Group
Well, meanwhile I could repair the 55V supply. The VR725 diode, 9,1 v was open, replaced by a 9.1v/1W. This repaired the +55v, the +15v is ok.Now, the  +5 v  supply is +7.0v and the -8 v supply is -12v.
I checked the Q401,Q402,Q402, Q617 onboard and Q718 out of board, they seems to be good with an analog Simpson7 multimeter,
Just for checking the influence of one suplly in tho the other, I disconnected CR304 in collector of Q402 and connected it to a +5v supply, still the -8v gives -12v.
I suspect the U506 is faulty. The measures in U506 are:Pin Pin 
Pin 
 

Enviado do Yahoo Mail. Baixe o aplicativo

Em Terça-feira, 16 de Maio de 2017 3:42, David <@DWH> escreveu:


On Fri, 12 May 2017 01:30:57 +0000 (UTC), you wrote:

 
Dear David ,
Thank you very much for your attention and answer.
Confirming the tested voltages:-2450 => zero Volts
+110 => +110,8 Volts
-8 did not test

+15v= +15v5v gives 6.75 Volts (higher voltage)
What?  So the +5 volt supply is actually +6.75 volts?  If so that
needs to be fixed before all else.  A high voltage could damage the
logic circuits.

Re: 2235 Trigger on one channel

Tom Jobe <tomjobe@...>
 

Hi Kevin,
It's often quite easy to find out if they are fake after you get
them,...it's the "how do you know before you buy them" bit that we all
need to know <G>.
The CA3102E chips are not worth much, it's the shipping charge to the UK
that will run the total cost up.
I looked at the shipping charge at some of the CA3102E links I had found
on eBay, and two of them charge less to ship than I would have to pay to
ship you the parts from California via the US Postal system. The Chinese
vendors can ship for very low costs, but then which vendor would you
trust? Maybe someone will have a trusted Chinese vendor or a better idea
about how you could get a CA3102E chip to finish the repairs your 2235?
tom jobe...

On 5/18/2017 5:46 AM, KEVIN CLARK maverick.uk@... [TekScopes] wrote:

Hi Tom :-)

As Tom indicates I am in the UK. Thank you for the eBay links. How
does one tell
if they are fake?

Cheers

Kevin


On 16 May 2017 at 21:06 "Tom Jobe tomjobe@... [TekScopes]"
<TekScopes@...> wrote:


There are some new CA3102E arrays on eBay.
I believe Kevin is in the UK.
Here's one from Switzerland:

http://www.ebay.com/itm/CA3102E-IC-RCA-2x-5962-01-093-4610-/302278280934?hash=item46613086e6:g:yi0AAOSwnF9Y6mS7
Two of several from the US:

http://www.ebay.com/itm/INTERSIL-HARRIS-CA3102E-DIP-14-Dual-High-Frequency-/361788292835?hash=item543c433ee3:g:lXEAAOSwcLxYDh5H

http://www.ebay.com/itm/CA3102E-Original-New-Harris-Integrated-Circuit-/121052570211?hash=item1c2f4ba263:m:m-2FOnEaLRPmCo6nwF1MBzg
There are many available from China, some of which look like they might
not be fake.

http://www.ebay.com/itm/1PCS-CA3102E-Dual-High-Frequency-Differential-Amplifier-/221115321652?hash=item337b800d34:m:mdO4W1kfigq6oNKBsBWxfMw





On 5/16/2017 9:02 AM, David @DWH [TekScopes] wrote:

On 16 May 2017 14:03:52 +0000, you wrote:

Hi David

Been a little busy so took a while to get back to this. So today
lunch time I started to measure some voltages with my DMM as
suggested, results as follows, something a little amiss (I think?)

U555B Output pin 6 ch1 = 0.139V (0.2V) (0.06V error)
U555B Output pin 6 ch2 = 1.476V (2.5V) (1.02V error)

U310 Output pin 1 ch1 = -3.26V (-3.4V) (0.14V error)
U310 Output pin 1 ch2 = -2.443V (-2.1V) (0.34V error)
You can check the values of R314, R315, R317, R318, and R319 around
U310 but I think the answer is going to be that U310 is bad.

The signal into pin 1/11 is suppose to be low when channel 1 is
selected. When that happens, the output of U555B is disconnected
(pins 1/11 of U310 should not draw any current) and should reach all
the way to ground which is what we are seeing and U310 should be
working but it is not.

When the signal into pin 1/11 is high, channel 2 is selected but pin
1/11 draws more current from U555B. In this case, it is drawing too
much current indicating that either U310 is damaged or R314 and/or
R315 are open.

The fact that U555B is not reaching its full output is irrelevant
because under that condition, U310 should not be forwarding the
trigger signal anyway.

I also looked at the feed from the A3 Board Connection as follows:-

Pin 18 (6.2V) = 6.5V (0.3V error), this also shows (0V) for XY but
can't see how to check this on front panel.
Pin 32 (0.0V) = 0V
Pin 33 (5.0V) = 4.996V
Pin 34 (5.0V) = 4.996V

Some of the values are slightly higher / lower than they should be,
is this the issue?

No, nothing is wrong there.

I wonder if there are any good sources for CA3102 transistor arrays. I
do not see any so if you cannot find one, blast me an email with your
mailing address and I should be able to mail one to you. I will have
to pull it from a junked board but will test it somewhat.







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

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


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

Yahoo Groups Links


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

Re: 468 with no -2459 v

Samuel Rocha <py1dkw@...>
 

Dear Group
Well, meanwhile I could repair the 55V supply. The VR725 diode, 9,1 v was open, replaced by a 9.1v/1W. This repaired the +55v, the +15v is ok.Now, the  +5 v  supply is +7.0v and the -8 v supply is -12v.
I checked the Q401,Q402,Q402, Q617 onboard and Q718 out of board, they seems to be good with an analog Simpson7 multimeter,
Just for checking the influence of one suplly in tho the other, I disconnected CR304 in collector of Q402 and connected it to a +5v supply, still the -8v gives -12v.
I suspect the U506 is faulty. The measures in U506 are:Pin Pin 
Pin 
 

Enviado do Yahoo Mail. Baixe o aplicativo

Em Terça-feira, 16 de Maio de 2017 3:42, David <@DWH> escreveu:


On Fri, 12 May 2017 01:30:57 +0000 (UTC), you wrote:

 
Dear David ,
Thank you very much for your attention and answer.
Confirming the tested voltages:-2450 => zero Volts
+110 => +110,8 Volts
-8 did not test

+15v= +15v5v gives 6.75 Volts (higher voltage)
What?  So the +5 volt supply is actually +6.75 volts?  If so that
needs to be fixed before all else.  A high voltage could damage the
logic circuits.



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

Re: 2235 Trigger on one channel

Kevin Clark
 

Hi Tom :-)

As Tom indicates I am in the UK. Thank you for the eBay links. How does one tell
if they are fake?

Cheers

Kevin


On 16 May 2017 at 21:06 "Tom Jobe tomjobe@... [TekScopes]"
<TekScopes@...> wrote:


There are some new CA3102E arrays on eBay.
I believe Kevin is in the UK.
Here's one from Switzerland:

http://www.ebay.com/itm/CA3102E-IC-RCA-2x-5962-01-093-4610-/302278280934?hash=item46613086e6:g:yi0AAOSwnF9Y6mS7
Two of several from the US:

http://www.ebay.com/itm/INTERSIL-HARRIS-CA3102E-DIP-14-Dual-High-Frequency-/361788292835?hash=item543c433ee3:g:lXEAAOSwcLxYDh5H

http://www.ebay.com/itm/CA3102E-Original-New-Harris-Integrated-Circuit-/121052570211?hash=item1c2f4ba263:m:m-2FOnEaLRPmCo6nwF1MBzg
There are many available from China, some of which look like they might
not be fake.

http://www.ebay.com/itm/1PCS-CA3102E-Dual-High-Frequency-Differential-Amplifier-/221115321652?hash=item337b800d34:m:mdO4W1kfigq6oNKBsBWxfMw





On 5/16/2017 9:02 AM, David @DWH [TekScopes] wrote:
>
> On 16 May 2017 14:03:52 +0000, you wrote:
>
> >Hi David
> >
> > Been a little busy so took a while to get back to this. So today
> lunch time I started to measure some voltages with my DMM as
> suggested, results as follows, something a little amiss (I think?)
> >
> > U555B Output pin 6 ch1 = 0.139V (0.2V) (0.06V error)
> > U555B Output pin 6 ch2 = 1.476V (2.5V) (1.02V error)
> >
> > U310 Output pin 1 ch1 = -3.26V (-3.4V) (0.14V error)
> > U310 Output pin 1 ch2 = -2.443V (-2.1V) (0.34V error)
>
> You can check the values of R314, R315, R317, R318, and R319 around
> U310 but I think the answer is going to be that U310 is bad.
>
> The signal into pin 1/11 is suppose to be low when channel 1 is
> selected. When that happens, the output of U555B is disconnected
> (pins 1/11 of U310 should not draw any current) and should reach all
> the way to ground which is what we are seeing and U310 should be
> working but it is not.
>
> When the signal into pin 1/11 is high, channel 2 is selected but pin
> 1/11 draws more current from U555B. In this case, it is drawing too
> much current indicating that either U310 is damaged or R314 and/or
> R315 are open.
>
> The fact that U555B is not reaching its full output is irrelevant
> because under that condition, U310 should not be forwarding the
> trigger signal anyway.
>
> > I also looked at the feed from the A3 Board Connection as follows:-
> >
> > Pin 18 (6.2V) = 6.5V (0.3V error), this also shows (0V) for XY but
> can't see how to check this on front panel.
> > Pin 32 (0.0V) = 0V
> > Pin 33 (5.0V) = 4.996V
> > Pin 34 (5.0V) = 4.996V
> >
> > Some of the values are slightly higher / lower than they should be,
> is this the issue?
>
> No, nothing is wrong there.
>
> I wonder if there are any good sources for CA3102 transistor arrays. I
> do not see any so if you cannot find one, blast me an email with your
> mailing address and I should be able to mail one to you. I will have
> to pull it from a junked board but will test it somewhat.
>
>







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

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


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

Yahoo Groups Links


Re: 2235 Trigger on one channel

Kevin Clark
 

Hi David

Thank you for your guidance.

I have checked the resistors in the feed to the 3102E chips as suggested with
the following results. I checked them in circuit on the basis that I'm looking
for a difference between identical circuits with one circuit that's working and
one that has a problem, I hope this logic is ok and a sound basis?

So:-

Res Designation Ch1 (design value) = In circuit value, Res Designation Ch2
(design value) = In circuit value

R314 (576Ohm) = 424Ohm, R339 (576Ohm) = 424Ohm
R315 (576Ohm) = 424Ohm, R340 (576Ohm) = 427Ohm
R317 (1.82KOhm) = 1.082KOhm, R342 (1.82KOhm) = 1.084KOhm
R318 (1.00KOhm) = 779Ohm, R343 (1.00KOhm) = 777Ohm
R319 (1.58KOhm) = 1.024KOhm, R344 (576Ohm) = 1.026KOhm


I don't see any real difference between the two circuits to indicate a problem
with the resistors on channel 1, I am assuming the difference to design is the
in circuit influence.

So I considered that as these circuits are identical and if we believe that
potentially IC 3102E is bad on ch1 then my logic would say if I can remove the
chips successfully then swap IC 3102E from ch 2 into ch1 and see if problem goes
with chip? Any danger of damaging the chip other than physical damage of course.

Thanks

Kevin

On 16 May 2017 at 17:02 "David @DWH [TekScopes]"
<TekScopes@...> wrote:



On 16 May 2017 14:03:52 +0000, you wrote:

>Hi David
>
> Been a little busy so took a while to get back to this. So today lunch
> time I started to measure some voltages with my DMM as suggested,
> results as follows, something a little amiss (I think?)
>
> U555B Output pin 6 ch1 = 0.139V (0.2V) (0.06V error)
> U555B Output pin 6 ch2 = 1.476V (2.5V) (1.02V error)
>
> U310 Output pin 1 ch1 = -3.26V (-3.4V) (0.14V error)
> U310 Output pin 1 ch2 = -2.443V (-2.1V) (0.34V error)

You can check the values of R314, R315, R317, R318, and R319 around
U310 but I think the answer is going to be that U310 is bad.

The signal into pin 1/11 is suppose to be low when channel 1 is
selected. When that happens, the output of U555B is disconnected
(pins 1/11 of U310 should not draw any current) and should reach all
the way to ground which is what we are seeing and U310 should be
working but it is not.

When the signal into pin 1/11 is high, channel 2 is selected but pin
1/11 draws more current from U555B. In this case, it is drawing too
much current indicating that either U310 is damaged or R314 and/or
R315 are open.

The fact that U555B is not reaching its full output is irrelevant
because under that condition, U310 should not be forwarding the
trigger signal anyway.

> I also looked at the feed from the A3 Board Connection as follows:-
>
> Pin 18 (6.2V) = 6.5V (0.3V error), this also shows (0V) for XY but can't
> see how to check this on front panel.
> Pin 32 (0.0V) = 0V
> Pin 33 (5.0V) = 4.996V
> Pin 34 (5.0V) = 4.996V
>
> Some of the values are slightly higher / lower than they should be, is
> this the issue?

No, nothing is wrong there.

I wonder if there are any good sources for CA3102 transistor arrays. I
do not see any so if you cannot find one, blast me an email with your
mailing address and I should be able to mail one to you. I will have
to pull it from a junked board but will test it somewhat.





Re: Type 503 Oscilloscope Issues

Dave Casey
 

The fact that the new caps took significantly longer to charge until the
meter went out of range is a good sign that the old caps don't have a lot
of capacitance anymore; the comparison assumes that you still left the
multiple sections of the cans tied together for your tests.

If any of them are particularly leaky once they get up to working voltage,
then you may not see improved performance by the power supply until you
remove the offending part from the circuit. That is to say that temporarily
tacking on the new caps will not necessarily show signs of improvement if
the old caps have high leakage current and are still connected. Temporarily
connecting the new caps with the old caps disconnected before you go
through all the trouble of hollowing out the cans and making the
installation more permanent is a good test. I suspect you will see marked
improvement, but I've been wrong before.

Dave Casey

On Thu, May 18, 2017 at 1:29 AM, enchanter464@... [TekScopes] <
TekScopes@...> wrote:



Hello all,

From the past week, I only had the chance today to look at the scope (but
the new capacitors came in yesterday), so just reporting in:


Doing the simple resistance test on C682 and C684, with the leads
disconnected, both seemed to show a similar trend. C684, on the 20k
setting, gave only a very brief reading before going out of range, which
was the same on the 200k setting. C682, however, showed the out of range
instantly on both settings. As such, I tested both on the 2M setting, and
this time both showed a reading in range, and then rapidly went out of
range (although I know it was mentioned that this setting would complicate
the readings' accuracy from the caps' faults). I performed the tests both
on the analog meter and on a DMM to confirm.


With each test, I switched both probes to confirm the test worked in the
reverse direction, and again the same rapid increase to out of range
occurred. However, the difference between the two caps was in the voltage
measurements. C684 took on a voltage ~3.5 VDC when attached for 1 min,
while C682 only went up to 0.4 VDC (even when connected for 5 mins). I am
not sure if this is significant (since the caps are different ratings), and
I do not have a capacitance/ESR meter to check the findings, but compared
to doing the same tests on the new capacitors, the new ones have a much
more gradual increase in resistance over time from 0 ohm to out-of-range
(over the course of many seconds at 20k, to a minute or two on 200k).


I intend to replace the caps anyway since I have the new caps in, but I
won't be able to do that until possibly the weekend, as I forgot that my
dremel bit for metal cutting had broken (and I want to put the caps in the
original containers). Both caps are can-negative, but that should be okay
since I will not be using the leads from the original caps (just threading
through the new ones in the modded can).


If I have time tomorrow, I'll just temporarily connect the new caps in
place and see what effect that has on the scope's performance and the -100V
bus reading.


- Evan

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


Re: Type 503 Oscilloscope Issues

Evan
 

Hello all,

From the past week, I only had the chance today to look at the scope (but the new capacitors came in yesterday), so just reporting in:


Doing the simple resistance test on C682 and C684, with the leads disconnected, both seemed to show a similar trend. C684, on the 20k setting, gave only a very brief reading before going out of range, which was the same on the 200k setting. C682, however, showed the out of range instantly on both settings. As such, I tested both on the 2M setting, and this time both showed a reading in range, and then rapidly went out of range (although I know it was mentioned that this setting would complicate the readings' accuracy from the caps' faults). I performed the tests both on the analog meter and on a DMM to confirm.


With each test, I switched both probes to confirm the test worked in the reverse direction, and again the same rapid increase to out of range occurred. However, the difference between the two caps was in the voltage measurements. C684 took on a voltage ~3.5 VDC when attached for 1 min, while C682 only went up to 0.4 VDC (even when connected for 5 mins). I am not sure if this is significant (since the caps are different ratings), and I do not have a capacitance/ESR meter to check the findings, but compared to doing the same tests on the new capacitors, the new ones have a much more gradual increase in resistance over time from 0 ohm to out-of-range (over the course of many seconds at 20k, to a minute or two on 200k).


I intend to replace the caps anyway since I have the new caps in, but I won't be able to do that until possibly the weekend, as I forgot that my dremel bit for metal cutting had broken (and I want to put the caps in the original containers). Both caps are can-negative, but that should be okay since I will not be using the leads from the original caps (just threading through the new ones in the modded can).


If I have time tomorrow, I'll just temporarily connect the new caps in place and see what effect that has on the scope's performance and the -100V bus reading.


- Evan

Re: Tek and Darlingtons...

David DiGiacomo
 

On Wed, May 17, 2017 at 8:55 PM, edbreya@... [TekScopes]
<TekScopes@...> wrote:
So far the biggest array I've found with suitable arrangement is the CA3081 - 7 NPNs with common-emitter, so I can divide the input emitter current by 7. The output will be reflected in a PNP mirror, made from an MPQ3906.
Unfortunately, MPQ3906 transistors are not matched.

Have you looked at the BCV62?