• 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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#22
I have some 475V quad Sprague TVLU electrolytics in my tube amp, still going strong since I built it in the 70s.
Those were great capacitors. And they sounded better than other brands. I used lots of them building stuff.
I would use them today, if they were still made.
 
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#23
I often see electrolytic "can" multi-caps in Golden Age amplifiers from the late 1950s, early 1960s that still measure fine and work. They need to have been in fairly regular service and never been awakened to B+ after being a Sleeping Beauty for a decade or more. I reform electrolytics over about 24 hrs, increasing the voltage very gradually, and observing current draw and ESR (indirectly, by feeding them rectified AC and observing ripple). Rate of decrease of ripple seems to work as an indicator of "forming", so determines when and how fast to increase voltage.

Those that were abused by inactivity, then shock, usually can't be saved. The OP probably doesn't need to worry about that, fortunately.

BTW, those needing replacement can caps might try Hayseed Hamfest, who do beautiful new cans (look like spun stainless) with Nichicon 105C innerds, at Ham, not audiophile prices, 3 or 4 lug bases.

All good fortune,
Chris
 
#27
kouiky said:
Does this indicate that electronics which have not been used for years should not be started normally?
I ask, because many devices cannot be brought up slowly on a variac and must reach an operating voltage threshold almost immediately for them to be stable.
Click to expand...

Maybe use an external supply initially to test the circuit, while disconnecting the old caps for reforming.
 
#29
kouiky said:
Does this indicate that electronics which have not been used for years should not be started normally?

I ask, because many devices cannot be brought up slowly on a variac and must reach an operating voltage threshold almost immediately for them to be stable. This is a bit of a pickle.
Click to expand...

If it’s possible, I try and start switching power supplies with a resistor load. Not worth risking a rare piece of equipment to a supply that might release magic smoke. Anything with a linear supply will be fine with a variac.
 
#31
We are talking about ~80 years old parts, not the usual vintage parts of the sixties or seventies. Great technological progresses were made from the sixties, and I doubt that WWII caps can be saved, except special parts, sealed under vacuum which were eye-watering expensive at the time.
Wirewound resistors, tubes, inductors, etc. should mostly be OK but the rest should be kept for decorative purposes only
 
#32
Yeah, and in this special case (only) the OP is a visual artist with possibly some priorities that might differ from most of us. Don't know, can't say, but maybe true-ish. Others have commented on restoration of classics, and we've not really been pertinent. The predictably great WWII milsurp are valves (that still have vacuum, or can be resuscitated, like Eimac's) and MIL-T-27 potted and welded into steel cans, transformers and chokes. Now going, going, gone.

All good fortune,
Chris
 
#34
The optimistic?

Functionally, you want fresh as possible Japanese made 105C or better electrolytics. But sometimes in restorations some adjustments are made for authenticity, preserving resale value, all that. None of us actually "need" museum quality things, but we'd all like to have a real WWI 1911. And it be all original. Don't lie - you know you want it.

Arf!,
Chris
 
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#36
 
#40
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!
 
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