i know that electrolytic capacitors stored for long periods when they are energized have high leakage current, if i buy a new pc power supply that has been stored for a long time in the electronics company warehouse when assembling the pc and turning it on there is the risk from the source cause serious damage to the machine because of the capacitors that were stopped for a long time
?
It's unlikely for it to be stored for long enough for that to be an issue. You can also jumper green to black to test it before installing into a machine.
No, they'll just leak some current internally for a few seconds and then it will taper off. I just got done testing some very, very old capacitors recovered from some equipment and the leakage was nowhere close to being a problem even with fairly large capacitors and a low current supply. A PC power supply won't even miss the few tens of mA leakage.
The time frame of concern is more like 40 years.
A few years ago I bought a HuanYang frequency inverter and it suggests that if it has long periods without being used then to at least power it up for a few hours once a year.
A bit of leakage in the main capacitors is not such a big problem. It's mostly when leakage becomes so big that the capactitors start heating up because of the power dissipation because of the leakage.
So a simple precaution is to to measure capacitor temperature in a powered, but further unused supply. If they get hot, there is definitely something wrong.
You can of course also measure the leakage directly or indirectly.
Measuring it directly would require opening the thing, and that is a chore, but you can measure the power consumption of the whole power supply, and when idling it should be pretty low. Write it down together with some other notes and a date and stick the piece of paper to the power supply.
If you take it out of storage a few years from now, and idling power is higher, then it's probably the caps, and you can attempt any of the "reforming" procedures.