I found a huge cap-like looking part in an old parts bin of mine. I tried making sense of its marking and I don't really understand what they mean. I googled for the part number and I found eBay listing and such, suggesting it's indeed a cap according to the eBay category, but even there I didn't find further information about the specs of this thing (somewhere it was suggested it's a 40uF 1250V cap but I don't see 40 anywhere written on the part).
Testing it with my component tester delivers very weird results: it's detected as a diode but also with 1.8mF capacitance…?! (usually the tester works nicely and rarely lies to me)
Can you help me identifying this?
EDIT: Interestingly, while playing with it again, the tester detected it once as capacitor, with 1759uF and 7.9 ohms ESR. But I can't reproduce it, now it's back to the diode rubbish… Anyway, I don't get how to read these markings correctly.
EDIT2: Multimeter gives me 1755uF.
Best Answer
"1250 MFD" is 1250 µF — it's a capacitor.
"50 W.V." is 50 working volts.
Specifically, it's an electrolytic capacitor. If your tester is feeding it AC, it might identify it as a diode, because of the reverse leakage current.
When it does identify it as a capacitor, it isn't surprising that the value is off by quite a lot. Tolerances weren't tight to begin with, and this unit has some age to it, which probably means a lot of drift in the value.
You could try connecting it to a power supply of about 25V or so for a while to see if this re-forms the oxide layer. Pay attention to the correct polarity! If the electrolyte hasn't dried out completely, this might allow your tester to identify it more reliably.