[AMPS] Noises in electrolytic capacitors

Wed, 26 Sep 2001 07:38:49 EDT

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Hello All,

Back in June I posted a question about a failed electrolytic in my Henry 2KD 
Classic. The consensus was that: 1. that the arcing and white discharge from 
the cap indicated venting of the electrolyte (a confirmation of what I 
thought I knew already) and 2. all the caps were probably of similar 
condition, or close to it and should be replaced.

I finally got around to changing them when a friend swapped a "new" set of 
caps for some gear I had. They were bought to replace caps in a Henry VHF 
amp. They are Mallory 210uf, 450V, 85C (sri Rich) with the following date 
code: 659-9918-371. Here's the rub.

Although there is no indication of voltage change on the panel HV meter, I 
get a metallic "clink" every so often from the caps. I have used the lights 
out method to look for arcs (which revealed the initial problem) and thought 
I may have had an arc from the HV wiring to the panel CW/SSB switch but have 
pretty well ruled that out. I can find no evidence of arcing.

I did try running them at about 500V in the amp by pulling the tubes and 
running low line voltage to condition the caps. They went more than an hour 
with no sound, but started again as soon as I went back to normal line 
voltage.

Should I test for leakage, and if so how? Is this phenomenon well-known in 
metal-can electrolytics (with a problem, obviously)? One knowledgeable member 
on the reflector that I contacted directly concluded that an internal arc in 
the caps would show up on the HV meter.

Without just replacing all the caps and tossing these, can someone suggest 
what the exact nature of the problem is and how to isolate it, perhaps to a 
single cap without buying one more and sequentially swapping it in?

Your thoughts would be appreciated.

73, Mark

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<HTML>Hello All,
 
 Back in June I posted a question about a failed electrolytic in my Henry 2KD Classic. The consensus was that: 1. that the arcing and white discharge from the cap indicated venting of the electrolyte (a confirmation of what I thought I knew already) and 2. all the caps were probably of similar condition, or close to it and should be replaced.
 
 I finally got around to changing them when a friend swapped a "new" set of caps for some gear I had. They were bought to replace caps in a Henry VHF amp. They are Mallory 210uf, 450V, 85C (sri Rich) with the following date code: 659-9918-371. Here's the rub.
 
 Although there is no indication of voltage change on the panel HV meter, I get a metallic "clink" every so often from the caps. I have used the lights out method to look for arcs (which revealed the initial problem) and thought I may have had an arc from the HV wiring to the panel CW/SSB switch but have pretty well ruled that out. I can find no evidence of arcing.
 
 I did try running them at about 500V in the amp by pulling the tubes and running low line voltage to condition the caps. They went more than an hour with no sound, but started again as soon as I went back to normal line voltage.
 
 Should I test for leakage, and if so how? Is this phenomenon well-known in metal-can electrolytics (with a problem, obviously)? One knowledgeable member on the reflector that I contacted directly concluded that an internal arc in the caps would show up on the HV meter.
 
 Without just replacing all the caps and tossing these, can someone suggest what the exact nature of the problem is and how to isolate it, perhaps to a single cap without buying one more and sequentially swapping it in?
 
 Your thoughts would be appreciated.
 
 73, Mark</HTML>

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