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Old 12th March 2013, 10:18 AM   #21
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Reforming Electrolytic Capacitors

Gajanan Phadte
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Old 12th March 2013, 11:17 AM   #22
forr is offline forr  France
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Quote:
Think of a 3300 uF reservoir cap measuring only about 100 uF. The capacitors that were mounted close to the heatsink had degraded most.These caps were significantly younger than 40 years, but they all required replacement.
I agree that heat is the ennemy for electrolytics. Some degrade much faster than other, it depends from the manufacturer. In case of doubt, a conservative measure is to replace electrolytics older than 20 years.
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Old 12th March 2013, 07:57 PM   #23
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and the good ones are also extremely expensive
I laugh only when i read that they do not form or reform but it is just the ear that adapts to the sound
I am listening to a little nad c352
It was left unused for 6 months
At the beginning I was very perplexed about the sound ... after some 100hrs it is quite better
The only possible cause are the caps ... not any other components
These electrolytic caps are a nightmare
They change with time like no other component
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gino
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Old 12th March 2013, 08:19 PM   #24
DF96 is offline DF96  England
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An electrolytic will generally reform in under 24 hours or not at all. 100hrs changes are more likely to be your ears/brain getting used to the sound. There may be some minor changes in leakage over a longer period but these should not affect sound. If leakage is an issue then an electrolytic should not be used at that point in the circuit.

6 months powered off will require a few minutes reforming at most.

Last edited by DF96; 12th March 2013 at 08:20 PM. Reason: 6 months
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Old 12th March 2013, 09:34 PM   #25
Elvee is offline Elvee  Belgium
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Quote:
Originally Posted by ginetto61 View Post
They change with time like no other component
I could name a few counterexamples: beloved tubes for one, carb comp resistors, paper capacitors (the dodgy ones) mylar capacitors (the ones that copied the dodgy metalization processes from the dodgy paper caps).... etc

In short, I'd trust better a well used and well (over)heated Siemens axial E-cap from the early seventies than many other components, older, younger or contemporary: even Ge transistors of that time can have unpleasant surprises in store
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Old 12th March 2013, 09:59 PM   #26
timpert is offline timpert  Netherlands
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Just today I started refurbishing a tube power supply. Actually, two identical units. First, I took the capacitors out and measured them. To my surprise, the reservoir caps of one unit all measured 55uF per section, where the can says 50 uF. And they pass the leakage test. These caps are 60 years old and well used! With the other unit, I was not so lucky, I had to replace all electrolytics, because they degraded. One section even seemed to have vanished entirely (measuring only 300 nF).

The units are full of carbon-comp resistors. Many of them are out of spec and have to go. Luckily, they are all very accessible. The last components that give me a headache are the selenium rectifiers. I am suspicious that they have a bit more voltage drop than they should, and that they will overheat in time due to this. When that happens, the result will be very unpleasant.

All in all, the result will be a set of almost fully rebuilt power supplies. I had hoped to get away with it a bit cheaper, but then I can not ensure safety and reliability.

Last edited by timpert; 12th March 2013 at 10:03 PM.
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Old 13th March 2013, 10:11 AM   #27
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Quote:
Originally Posted by DF96 View Post
An electrolytic will generally reform in under 24 hours or not at all.
100hrs changes are more likely to be your ears/brain getting used to the sound.
There may be some minor changes in leakage over a longer period but these should not affect sound.
If leakage is an issue then an electrolytic should not be used at that point in the circuit.
6 months powered off will require a few minutes reforming at most.
Thank you very much for your valuable reply
I did not know about the 24 hours only. This is nice (I do not like to wait)
I strongly think i will replace those two caps with something new
Thanks again
Kind regards,
gino
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Old 13th March 2013, 10:17 AM   #28
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Quote:
Originally Posted by Elvee View Post
I could name a few counterexamples: beloved tubes for one, carb comp resistors, paper capacitors (the dodgy ones) mylar capacitors (the ones that copied the dodgy metalization processes from the dodgy paper caps).... etc
In short, I'd trust better a well used and well (over)heated Siemens axial E-cap from the early seventies than many other components, older, younger or contemporary: even Ge transistors of that time can have unpleasant surprises in store
Hi ! the problem with aging is that caharacteristics are time dependant
I do not feel comfortable with a sound changing with time passing
I find it disorienting
Unfortunately caps are caps
thanks and regards,
gino
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