Have just been making a minor repair to a nicely made, home built multi-voltage power supply that I picked up from a UK vintage radio club auction some time ago. The unit was made to substitute mains power at various preset voltages to supply older transistor radios. So it has 3v, 4.5v, 6v, 9v, 12v and 18v settings, plus a fully variable position. It's based around a TO3 variable linear regulator, with switch selected presets to set the output voltages. Quite a neat little unit, nicely built and very useful.
So, having used it for a number of years I decided to have a peek inside to make sure everything looked ok, good thing I did because one of the 2 4700 uf reservoir caps had started to puke itself!
So, checked the value and voltage and obtained a couple of nice Panasonic replacements. Had to mod the mounting arrangement because the original, older caps were much larger. Did all that so it looked ok to my OCD vision, turned on and all was working fine. Here is the doh' moment though, I decided to check the voltage across the caps and discovered to my horror it was 10 volts higher than the rating of my nice new caps
Even though the new caps were exactly the same rating as the old caps, at 25 volts! So the original constructor had either thought, oh it'll be ok, or never noticed the error! No wonder that original cap had started to puke!
So, a reminder for me, don't take anything for granted!
All my careful mounting will now have to come apart and new caps bought, bu66er!!!
Although, I do wonder how long those new caps would last running at 35 volts
No, stop it!