Quote:
Originally Posted by madlabs
I am not planning to test caps in old gear with en eye to re-use except micas and ceramics to see if they are ok to keep or need replacing, as one would usually prefer to keep those. I'm sure I will check old paper caps for a while as they are pulled out just educate myself on how many are bad and just how bad they are. I'd also use it to check new caps before installation, not just that they are good but that I have the right value.
And I just figured out that it is much closer than I thought. I decided to re-check my leakage test with resistors and realized that with the leakage range switch set correctly for the DUT that it is pretty close. Good enough, I'm happy with that.
So, is there a rule of thumb for unmarked/unknown mica and ceramic caps for leakage? I'm trying to get an idea for when trouble shooting for those times when they do go bad. Same for paper caps, what would likely still work and what is just plain shot?
Pretty happy with it for a freebie.  Only bummer is that it kinda shoves my Heathkit C3 with its lovely magic eye off the bench.  |
99% of the ceramic and mica caps give an error when testing on my LC102 - no detectable leakage. In 38+ years of repairing electronics, I've seen exactly two mica caps that were leaky. I've seen one leaky ceramic - it burned, in fact, in a Motorola B/w set, a victim of high humidity and being in a smoker set...
Tubular ceramics? (White or off-white body, color dots along the cylinder) -Leave 'em alone - they are never bad, and are in some circumstances fragile, so let them be. Dipped micas, leave them alone. Chiclet micas/Dot code micas, give them a check for value - if good, leave them alone. Disc caps - usually they drift (as they should, by the tempco..) but rarely fail, and when they do, spectacularly. Paper/Wax/Bumblebees/Black Beauties/Elmenco ceramics? Gotta go...
On the Electrolytic side, everything older than the year 2K should be checked and replaced as needed - but some brands demand replacement - namely the
Callins caps - black with red ends, particularly found in Zenith TVs and radios.
A little experience under your belt with the LC76, and you'll soon be a wizard with caps....
