• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

Do capacitors go bad if they are not used?

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#41
rayma said:
Maybe use an external supply initially to test the circuit, while disconnecting the old caps for reforming.
Click to expand...

The problem is, I can’t envision myself disassembling an entire amplifier to reform every capacitor. If I go to that length, I might only attempt to reform the large main supply capacitors - everything else would get replaced. Even old Black Gates, I would probably replace them with modern Panasonics or Nichicons with appropriate ripple current ratings and “hours @X temperature” specifications.

My unwritten motto has been to replace them. The worst was desoldering them from double-sided boards where there was a solder joint on both sides and both leads needed to be heated simultaneously.
 
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#43
In a finished valve amplifier, all valves should be removed before any reforming process, including any valve rectifiers. No sense beating them up by running at low filament temps while Variac'ing. If you do this often, folk make up an octal 5T semicon replacement from an octal base, or you can just tack a pair of 1N4007s on the socket. Be sure to watch unloaded downstream voltages; temporarily add substitute loads if needed.

Strangely, I see most all low voltage old electrolytics, like cathode bypass caps, bad in old gear. No idea why.

All good fortune,
Chris
 
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#46
Kay Pirinha said:
That's right, Marcel, and it also holds true for German WIMA Durolit capacitors, even though they carry that trustworthy, triangular VDE symbol.

My experiences with these are just the reason why I keep warning from paper capacitors in general. This is nothing else than an outdated technology.

Best regards!
Click to expand...
I took some money in the past thanks to RIFA caps.
Several C.R.T t.v sets had come in for repair due to burned fuses+caps.
This is how I paid some of my son's education expenses!
 
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#49
1702834360172.png


This is the RIFA cap that fizzled on me last week. The stink takes a long time to clear out.
 
#53
In fact, what I mistook for WW resistors are inductors, and they are in pristine condition. What are you going to do with them? I don't know. Some Hams would find them useful, bur for audio projects, they are mostly useless. Class D maybe?
 
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