I just picked up 3 boxes of WWII radio repair parts that have never been used. Mainly tubes, transformers, resistors, and can caps. All of it is NOS so are the caps no good?
Depends on the capacitor type. An electrolytic may be dried out and dead, or needs to be reformed, or (not very likely) may be good as it is. Paper capacitors most probably are leaky. Film foil capacitors may be good, as are ceramic types.
Best regards!
Best regards!
Some pictures would be nice! I suppose the quality of the parts could also be a factor. I have a lot of Sprague electrolytics from an old oscilloscope and I will test them before discarding them.
Also to remember is the value tolerance of those capacitors from 80 years ago was
abysmal when new, compared to what are produced today.
abysmal when new, compared to what are produced today.
Save the tubes and transformers, throw away the rest. I don't know in what conditions it was stored, and it is quite old and maybe the wire insulation on the transformers is bad, and that is dangerous. If the iron is good, maybe they can be rewound for some purpose. Tubes should be tested as well.
If the capacitors are bad, don't throw them away but donate them to a vintage radio society. They can always remove the contents of the cans and hide new capacitors in them to turn them into vintage-looking good capacitors for vintage radio restoration.
A few years ago I inherited a bunch of military / HAM radio gear and parts from that era.
Initially I thought most of it would be useless junk but I was pleasantly surprised how quickly everything sold on eBay.
There are still a lot of radio guys out there, so I wouldn't toss anything without trying to sell it first.
Like this?
Attachments
Yes, but preferably with the correct value and working voltage...
You can reform electrolytic caps with a power supply through a high value series resistor, say 100K 5W. Turn up the voltage close to the caps' voltage rating, say 250-450VDC, and let it "cook" overnight. If the voltage is brought up to spec, they are good to go. But if it's low, toss them.
Most if not all of the capacitors will be stale: E-caps obviously (yet I am a prominent advocate of old(er) E caps use), paper caps because paper is not durable and water-ingress measures in effect at the time were futile, mica caps will also suffer from ambient conditions (some might be OK but need testing).
Some glass or mica types are very durable, but they were the exception.
Carbon composition resistors with an organic binder will be completely out, the mineral types might fare better, but their initial tolerance will generally be exceeded, even if it is 20%.
Some components come in a vacuum glass-sealed vessel: resistors, capacitors, etc. and they are probably still OK, but they were rare and expensive.
Vacuum tubes could survive, but there is no general rule: some might have become gassy, due to internal parts or leaks; they need testing to assess their quality
Some glass or mica types are very durable, but they were the exception.
Carbon composition resistors with an organic binder will be completely out, the mineral types might fare better, but their initial tolerance will generally be exceeded, even if it is 20%.
Some components come in a vacuum glass-sealed vessel: resistors, capacitors, etc. and they are probably still OK, but they were rare and expensive.
Vacuum tubes could survive, but there is no general rule: some might have become gassy, due to internal parts or leaks; they need testing to assess their quality
If you don't want to spend the time reforming, then don't bother, "donate" the caps somewhere.
Yes, the tolerances of older electrolytic capacitors were pretty high. I recall seeing +80/-20% but it'll still make a decent supply filter cap at any value in its range.
It only takes a minute to set up, but it can take hours (sitting by itself, away from people and pets that might want to touch) to reform - if/when the cap gets to 98% or so of the power supply voltage, it's probably good. Be sure to discharge it with a lower value resistor.
The word "cook" here worries me a bit - the idea is to reform them without putting in enough power to warm them up. The limitation is current, and 10mA is a good upper limit for reforming higher voltage electrolytics. The 100k resistor value looks good, that will give 4.5mA at 450V.
Yes, the tolerances of older electrolytic capacitors were pretty high. I recall seeing +80/-20% but it'll still make a decent supply filter cap at any value in its range.
It only takes a minute to set up, but it can take hours (sitting by itself, away from people and pets that might want to touch) to reform - if/when the cap gets to 98% or so of the power supply voltage, it's probably good. Be sure to discharge it with a lower value resistor.