(From: Clifton T. Sharp Jr. (
[email protected])).
I still do just enough work that I'll one day break down and buy an ESR meter
(I always give in and indulge myself with the toys of my "trade"). For now,
though, the quickie method I use is the oscilloscope. It goes something like
this:
1. Scope positive lead. Any significant AC? If not, go to next cap.
2. Is the AC more than about 5% of the DC? If not, note this location and
go to next cap.
3. Scope negative lead. AC here roughly the same as on positive lead? If so,
go to next cap. (If this lead is *obviously* grounded, skip this step.)
4. Set off; note value; jumper in roughly same value at safe voltage rating.
(Note: make sure both caps are discharged! --- sam)
Set on; scope positive lead. Significant difference? If not, note this
location and go to next cap.
5. Replace cap. Test set. If not okay, go to next cap.
If that doesn't catch it, a quick review of the "noted locations" often does.
This fixes 98% of cap problems. Not exhaustive or perfect, nor is it intended
to be.