I've just gotten through replacing capacitors on a trio of dead LCD screens (nothing's blown up yet, so far) - they either had one or two capacitors on their inverter circuit SLIGHTLY bloated, and not quite leaky. I ended up replacing all capacitors of the same brand/'colour', even the ones that looked fine, in case.

Now, checking a bad resistor is simple - i can use a standard multimeter to test it, and i tend to check my solders with the continuity testing option of the multimeter.

How would i test a capacitor ? Is there some standard, common way to test one?


3 Answers 3


Charge thru a resistor to the working voltage. Choose a resistor so RC (where R is the resistance, C is the capacitance, and RC is the time constant) is workably large. The final voltage should equal the applied voltage - IR, where I is the leakage current. The rate of charge will give you C ( if I is large you will need to correct for that ) This ignores the burden of the meter which is probably above 1 meg and for a supply cap probably does not matter.


Use a DMM with capacitance measuring. If you don't have one, try charging and discharging the cap through a resistor and measuring the voltage curve.

  • 3
    \$\begingroup\$ Capacitance mode of DMM won't show if an electrolytic is dried enough to make the circuit do not function properly. I tried that, lol :) \$\endgroup\$ Commented Dec 25, 2011 at 15:33

Even though this is a very old question, I feel like I have something useful to add here, so I will answer it anyway.

The standard, common way to test a capacitor is to use an instrument called an LCR meter. This is a device similar in appearance and usage to your standard multimeter, but which measures inductance, capacitance, and resistance (hence "LCR"). LCR meters measure more figures of merit as well, however; you can use one to measure the equivalent series resistance of your capacitors, which is very important for power supply filter caps, and a better indicator of a failing electrolytic capacitor than capacitance alone.

Some, though I don't think all, LCR meters will even tell you the equivalent series inductance of your capacitor, self-resonant frequencies, and all sorts of other useful and useless data.

Unfortunately, good LCR meters don't come cheap. Low-end LCR meters (from reputable brands) are generally more expensive than equally low-end multimeters. A quick google search shows the Agilent/Keysight U1733C priced around $600, and even the cheap Extech brand one is over $200.


Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.