> "Phil Allison"
>>>I have an LCR meter which shows the ESR for electrolytic caps,
>>** Make and model please.
>>> but I have no idea how to interpret this number.
>>** As with any measurement, you must know what to expect or it is
>>meaningless to you.
>>> How do you know if a cap is shorted or boardering on that status?
>>** Use an ohm meter.
>>The reading should be tens or hundreds of thousands of ohms.
> One fun thing about electrolytic caps is that they store and even generate
> voltages, through dielectric absorption and electrochemical effects. That
> really fool a DVM on its ohms range, especially if you let it auto-range.
** Quite so.
FYI: by "ohm meter" I meant an analogue one, ie a moving coil
multimeter. In any case, a shorted electro would show up on a
DMM quite reliably.
The OP is asking the impossible cos verifying some old electro
is still OK requires a bank of tests, meters and PSUs.
Where possible, after doing an ESR test, I just switch old equipment
on and watch out for smoke.
I had a new in box power amplifier for repair some years back that
insisted on blowing its AC fuse at switch on. However, I found it
could be brought up gradually using a Variac, pulling a large AC
current if done too fast.
Made in Germany it used a pair chassis mount, 30mF, 100V Siemens
electros in the PSU - the kind with 5mm bolts on top.
Both were getting damn hot and even after an hour the Variac was
set not much beyond half mains voltage - so I stopped torturing them.
Turned out, the amplifier had been left in storage for about 2 years
and the electros had depolarised something fierce.