how to check capacitors on old PCB boards
how to check capacitors on old PCB boards
(OP)
Hello,
We need to check aged electrolytic capacitors on PCB boards to see if capacitances still available or not. Per some manuals of component testers, the methods to take actual characteristics of capacitors the capacitors should taken off from boards. Taking them off from boards troubles me. Once the they taken off from boards, they might not be weld nicely back to board. Therefore I am trying to ask if there any alternative testing methods. Thank you all.
We need to check aged electrolytic capacitors on PCB boards to see if capacitances still available or not. Per some manuals of component testers, the methods to take actual characteristics of capacitors the capacitors should taken off from boards. Taking them off from boards troubles me. Once the they taken off from boards, they might not be weld nicely back to board. Therefore I am trying to ask if there any alternative testing methods. Thank you all.





RE: how to check capacitors on old PCB boards
Dan - Owner

http://www.Hi-TecDesigns.com
RE: how to check capacitors on old PCB boards
The caps on PCB boards has already stored in warehouse orver five years. I am worried their capacitance still ok good or not. Therefore I would like to check their performances before those boards join into operation. I may provide some field pictures later.
RE: how to check capacitors on old PCB boards
Mike Halloran
Pembroke Pines, FL, USA
RE: how to check capacitors on old PCB boards
I think I was stuck in this question.
Thanks for your solution. That's easier and cheaper.
RE: how to check capacitors on old PCB boards
Either test them In Circuit, or perform a functional test of the circuit card.
Five years isn't that long. It's likely that there's no problem.
RE: how to check capacitors on old PCB boards
The Al2O3 insulating layer deteriorates when the capacitors stay at zero volts and that increases the leakage current initially when voltage is applied. The Al2O3 layer is then quickly reformed when voltage is applied and I have necer had any incidents with small electrolytic capacitors - say 10 000 uF at 35 V or 100 uF at 350 V, the latter is common in old radio sets.
If you really want to make sure that there's no problem, I think that connecting those boards to nominal voltage for a while, say around ten minutes, will reveal any bad capacitors. But I doubt that you will find any.
An example: I do collect old radio sets and I have some from the thirties, fourties, fifties and so on. I was very careful when I switched the first ones on. Half the voltage, series incandescent lamp and all that. Never a problem. Nowadays I just switch on - even if it is a fifty years old set. And, again, never a problem.
Gunnar Englund
www.gke.org
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Half full - Half empty? I don't mind. It's what in it that counts.
RE: how to check capacitors on old PCB boards
RE: how to check capacitors on old PCB boards
RE: how to check capacitors on old PCB boards
"Power capacitors" are a much greater risk than smoothing capacitors and they are in their turn somewhat riskier than capacitors in RC filter applications, where the risk is zero.
Leakage currents reduce themselves when voltage is applied. Increased ESR is only a risk in power capacitors with high ripple current. And increased ESR cannot be reduced through reforming. If low ESR is important (like in SMPS and VFDs), all you can do is to test and replace. But increased ESR usually comes from operation and not from storage over long time.
The rest of the answer is: It depends. It depends on capacitor make, temperature and other things.
Gunnar Englund
www.gke.org
--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.
RE: how to check capacitors on old PCB boards
Dick Smith is an Australian electronics store that used to sell components and kits etc. Nowdays they sell TVs and stereos :(