Cursitor Doom wrote:

I don't think any of us here would take some semi-ancient item of
electronic equipment of unknown provenance and just plug it in the mains
socket and switch on. We know from experience or elsewhere that is not an
advisable thing to do. So we typically gently wind up the voltage via a
variac over an extended period of time. But is that enough? I read
somewhere one should also monitor the current drawn by the equipment as
one does this. I admit I've never been quite that fussy, but would be
interested in hearing what others think about this rather more cautious
approach and if it actually achieves anything worthwhile.
If not tantalum capacitors, and simple linear power supply, then this is
usually a good idea.

Tantalum caps can also be helped by this, but appluing very small voltages
for a long time (a day or so) may be better before more power is applied.
Replacing them is another way to go.

Slowly ramping up voltage is not generally compatible with switching
supplies.

Jon