Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems.

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Default Do these 'lytics need to be replaced?

Are these "bulging"? How much bulge is too much? Or is _any_ bulging
to much? "If you can see that it's not flat, it's too much"?

https://imgur.com/GymXlUb

Thanks,
Bob
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Default Do these 'lytics need to be replaced?

On Tue, 14 May 2019 09:54:39 -0400, Bob Engelhardt
wrote:

Are these "bulging"? How much bulge is too much? Or is _any_ bulging
to much? "If you can see that it's not flat, it's too much"?

https://imgur.com/GymXlUb

Thanks,
Bob


I had a few years refurbishing old equipment. I routinely replaced
power supply electrolytics as they were always suspect. I've found
some electrolitics that were not bulging but had no measurerable
capacitance.

I remember an Italian TV signal and video generator that had banks of
electrolytics wired in parallel rather than using high capacitance. It
was a good idea as small capacitors lasted longer than large ones. I
still changed them all!

Steve
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Default Do these 'lytics need to be replaced?

On Tuesday, May 14, 2019 at 9:55:17 AM UTC-4, Bob Engelhardt wrote:
Are these "bulging"? How much bulge is too much? Or is _any_ bulging
to much? "If you can see that it's not flat, it's too much"?

https://imgur.com/GymXlUb

Thanks,
Bob


Bulging is not an indication of the condition of a capacitor. I've seen many physically large capacitors in power supplies show some bulge and be dead on for value and ESR, and others that looked brand new and were decidedly low in value and high in ESR.

Either pull them and test them or at least scope across them (watch for hot ground with your scope).

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Default Do these 'lytics need to be replaced?

On 2019/05/14 8:23 a.m., John-Del wrote:
On Tuesday, May 14, 2019 at 9:55:17 AM UTC-4, Bob Engelhardt wrote:
Are these "bulging"? How much bulge is too much? Or is _any_ bulging
to much? "If you can see that it's not flat, it's too much"?

https://imgur.com/GymXlUb

Thanks,
Bob


Bulging is not an indication of the condition of a capacitor. I've seen many physically large capacitors in power supplies show some bulge and be dead on for value and ESR, and others that looked brand new and were decidedly low in value and high in ESR.

Either pull them and test them or at least scope across them (watch for hot ground with your scope).


In this case (I checked the photo) the bulging is certainly indicative
of a dying capacitor. Another clue is the black plastic sleeve has
pulled away from the top of the cap. As a matter of course we replace
any caps where the sleeve has shrunk - that is an indication of the cap
overheating or simply being in too hot an environment. A new cap has the
sleeve covering around 25% of the top of the cap, if you can see signs
of shrinkage then time to test and likely replace the cap.

As an aside, it is interesting that early amplifiers put all the
transistors in sockets (pretty reliable devices actually) and yet
soldered in the most failure prone part of all - the caps! Only on the
odd rare tube equipment did you see electrolytic cans that had an octal
style plug. Of course if the caps were in sockets then you would have
one more junction to fail (OK two junctions per cap) but at least you
could replace them more easily.

Ducking.

John ;-#(#

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Default Do these 'lytics need to be replaced?

In general, capacitors are relatively inexpensive such that if one is in any doubt at all, replace them. All and at the same time, an ESR meter is a helpful - but NOT absolute - screening tool.

Yes, those caps appear to be bulging Further, the shrink covering on them has pulled down from the top. A typical cap has that covering turning onto the top by some amount greater than what you show.

https://media.rs-online.com/t_large/F7152707-01.jpg

My guess is that they have gotten very hot, one or more times. Which would explain both the shrinkage of the covering and the bulge.

Peter Wieck
Melrose Park, PA


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Default Do these 'lytics need to be replaced?

On 5/14/2019 9:54 AM, Bob Engelhardt wrote:
Are these "bulging"?* How much bulge is too much?* Or is _any_ bulging
to much?* "If you can see that it's not flat, it's too much"?

https://imgur.com/GymXlUb

Thanks,
Bob


Thanks for all the prompt and helpful replies.

This is my step son's amp and I have decided that I'm not going to do
any repair that might not be perfect in his eyes. So I'm going to
return it and let him know that the caps should be replaced.
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Default Do these 'lytics need to be replaced?

On Tuesday, May 14, 2019 at 12:36:34 PM UTC-4, Bob Engelhardt wrote:
On 5/14/2019 9:54 AM, Bob Engelhardt wrote:
Are these "bulging"?* How much bulge is too much?* Or is _any_ bulging
to much?* "If you can see that it's not flat, it's too much"?

https://imgur.com/GymXlUb

Thanks,
Bob


Thanks for all the prompt and helpful replies.

This is my step son's amp and I have decided that I'm not going to do
any repair that might not be perfect in his eyes. So I'm going to
return it and let him know that the caps should be replaced.


"not going to do any repair that might not be perfect in his eyes"
Hmmm strange choice of words? How are you quantifying a 'perfect repair'?
Would 'perfect' mean replacing all components that may have been degraded? hence these caps are the first step. Do you suspect others? Carbon resistors change resistance with age...going to replace all of them?
How old is the amp? Is it experiencing any other abnormalities?
J
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Default Do these 'lytics need to be replaced?

On 2019/05/14 1:29 p.m., three_jeeps wrote:
On Tuesday, May 14, 2019 at 12:36:34 PM UTC-4, Bob Engelhardt wrote:
On 5/14/2019 9:54 AM, Bob Engelhardt wrote:
Are these "bulging"?* How much bulge is too much?* Or is _any_ bulging
to much?* "If you can see that it's not flat, it's too much"?

https://imgur.com/GymXlUb

Thanks,
Bob


Thanks for all the prompt and helpful replies.

This is my step son's amp and I have decided that I'm not going to do
any repair that might not be perfect in his eyes. So I'm going to
return it and let him know that the caps should be replaced.


"not going to do any repair that might not be perfect in his eyes"
Hmmm strange choice of words? How are you quantifying a 'perfect repair'?
Would 'perfect' mean replacing all components that may have been degraded? hence these caps are the first step. Do you suspect others? Carbon resistors change resistance with age...going to replace all of them?
How old is the amp? Is it experiencing any other abnormalities?
J


This might be the level of restoration where you hollow out the old part
and put the new part inside and then seal it back up... early vintage
(1920s) radio collectors enjoy doing that!

John :-#)#

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John's Jukes Ltd.
MOVED to #7 - 3979 Marine Way, Burnaby, BC, Canada V5J 5E3
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www.flippers.com
"Old pinballers never die, they just flip out."

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Default Do these 'lytics need to be replaced?

On Tuesday, May 14, 2019 at 6:55:17 AM UTC-7, Bob Engelhardt wrote:
Are these "bulging"? How much bulge is too much? Or is _any_ bulging
to much? "If you can see that it's not flat, it's too much"?

https://imgur.com/GymXlUb


That doesn't look like a problem at all. The "X" dents in the top of the
capacitor are a pressure-relief scheme, intended to rupture if steam
forms inside the capacitor, and there's no sign those are under stress.

A must-replace scenario is when the "X" has ruptured and fluid is seen leaking,
or (sometimes) the rubber seal on the other end of the capacitor has
failed, which sometimes lifts the entire aluminum shell. A significant
bulge but NO leaking means that there has been some overheating, which
can mean a rectifier has shorted and the capacitor is not the main problem.

Many low-ESR capacitor failures have occurred in recent decades, but these
look like general-purpose capacitors, not known for high failure rates. If they
are forty years old, replacement might be a good idea regardless.


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Default Do these 'lytics need to be replaced?

On Tuesday, 14 May 2019 14:55:17 UTC+1, Bob Engelhardt wrote:
Are these "bulging"? How much bulge is too much? Or is _any_ bulging
to much? "If you can see that it's not flat, it's too much"?

https://imgur.com/GymXlUb

Thanks,
Bob


The best answer is to test them for C & ESR. Or replace, bulging caps are usually bad.


NT
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Default Do these 'lytics need to be replaced?

On 5/14/2019 4:29 PM, three_jeeps wrote:
On Tuesday, May 14, 2019 at 12:36:34 PM UTC-4, Bob Engelhardt wrote:


Thanks for all the prompt and helpful replies.

This is my step son's amp and I have decided that I'm not going to do
any repair that might not be perfect in his eyes. So I'm going to
return it and let him know that the caps should be replaced.


"not going to do any repair that might not be perfect in his eyes"
Hmmm strange choice of words? How are you quantifying a 'perfect repair'?

....

The key part is the "in his eyes". I don't want to do work that _he_
might not find perfect. It's really annoying to do a favor and have it
criticized.
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