My question is about whether there would be a problem with aluminum electrolytic capacitors that have been installed in an amplifier, then factory tested (so a current was run through them), then stored for four years.
I know that the shelf life of electrolytic capacitors is 2-3 years. But I have read some say that if they have been mounted on a circuit board and have received a charge during testing at the factory, they can then survive for much longer than their shelf life that with no problems.At the same time, others claim that the shelf life holds also for caps in circuits, when starved of electrical current.
So, the question is: does the shelf life of electrolytic capacitors also apply to capacitors in amplifiers that have in the past received an electrical charge, but have then been put into storage for a long time, at room temperature, in dry conditions? Or does having received a charge make the caps more resistant to chemical degradation in the absence of further charges.
Best Answer
Shouldn't make any difference whether they are mounted or not.
The main factor in electrolytic capacitor lifetime is what temperature they are stored or used at and for how long at high temperature. Rule of thumb is that life halves for every 10°C rise.
So if they were stored in a cool place they'll have a long shelf life. If they were stored in an attic in Phoenix during the summer, less so.
Voltage was applied during testing at the factory (and before that to the raw etched foil), and it certainly leaked off within a short period after that.