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Home Forums 68kMLA How do you test diodes, resistors, and capacitors? — #13
Post #13 by Gorgonops
Source Forum68kMLA
CategoryHardware
Post DateFri, 11 Nov 2011 - 16:51
Original URLhttps://68kmla.org/bb/threads/how-do-you-test-diodes-resistors-and-capacitors.24200/
Post
I've personally had very little luck testing capacitors in-situ . . .Maybe that's just my experience, but I wouldn't trust a multimeter reading to diagnose a bad cap.
Have you used an ESR Meter at all? ISTR, 4sPhoto saying that he's had great success using one.
No, just the capacitance setting on my cheap multimeter. And looking at the prices of an ESR meter I think I'll stick with that. ;^b

(I could replace every capacitor on all of my Commodore PETs several times over for the price of the cheapest one I see.)

As noted, if the capacitor is sitting loose the multimeter seems to give a reading close to the rated value of the capacitor, which really is good enough to me. (Gives me a quick double-check to verify I'm installing the right one, as the markings on tiny capacitors can be really difficult to read and interpret.) But in the most recent particular case: I was repairing a bad 555 Timer-based RESET circuit which involved three capacitors, and in-situ none of them registered anything close to a sensible reading on the meter. I tested one, got excited that it looked off, replaced it, and it turned out to not solve the problem. (And the one I'd just installed "tested bad" once it was soldered in there.) So I tested the two remaining ones, they both gave funky readings, so I just said "screw it" and replaced them both at the same time. Problem solved, but I destroyed the capacitors when I snipped them off so I don't know which one was the bad one and I couldn't test after the fact. I'd be miffed, but really all it cost me was an extra 60 seconds with the soldering iron and about 3 cents for the extra capacitor.

Maybe a better meter works moar better. I have a *fantastic* $20 China Special.

mp.ls