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I'm trying to troubleshoot why my TV isn't turning on and was advised that it might be an issue with a capacitor. There are no visible signs of bursting or leaking on any of them so I've started measuring the resistance using a multimeter, however I have no idea what I'm actually looking for.

  • Testing a 35V 2200µF capacitor shows a gradually increasing resistance that plateaus at around 730Ω.
  • Testing a 25V 2200µF capacitor shows a gradually increasing resistance that plateaus at around 4.1kΩ.
  • Testing a 35V 1000µF capacitor shows a gradually increasing resistance that plateaus at around 9.85kΩ.
  • Testing a 450WV 150µF capacitor shows a gradually increasing resistance that eventually exceeds the measurement capabilities of the multimeter (2MΩ).

Is there any way to calculate what the resistance should be for a given capacitor? Or what readings would indicate a problem with one?

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    \$\begingroup\$ Are you removing the capacitors from the circuit board before testing them? If not, you're mostly measuring whatever is connected in parallel with the capacitor on the board. \$\endgroup\$
    – The Photon
    Commented Feb 5, 2015 at 23:53

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I'm guessing that you are measuring these capacitors WHILE they are still soldered to the PCB? If so, the resistance readings that you are getting are caused by the other components in the circuit.

Capacitors fail in a variety of ways. One of the more common problems is that the ESR of the capacitor increases to the point where the circuit will not operate. The cool thing about testing capacitor ESR is that it usually can be done while the capacitor is still soldered to the board.

Although there are several capacitor testers available commercially, it's fairly easy to build (or even bread-board) a simple tester that finds capacitors that have either failed OPEN or have had the ESR rise to unacceptable limits.

One such device is shown here: DIY Capacitor ESR Tester

You haven't said what kind of test equipment that you have available. Hopefully, this helps a little bit.

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  • \$\begingroup\$ Yes, they were still soldered to the PCB. Currently I only have a multimeter so building an ESR tester could be a bit much, but they also seem to be rather expensive. I might buy some spare capacitors and then detach the ones from the board for testing/replacement. Thanks for your help! \$\endgroup\$
    – DanielGibbs
    Commented Feb 6, 2015 at 1:18
  • \$\begingroup\$ Please visit the link that I provided. You will see that the person who made that Web page put his first version on a breadboard. You can do the same thing and use your existing multimeter as the display. \$\endgroup\$
    – Dwayne Reid
    Commented Feb 6, 2015 at 2:29
  • \$\begingroup\$ I don't really have a the skill to assemble something like that myself unfortunately. I think it'll be quicker and easier to just take the capacitors of the board for testing. \$\endgroup\$
    – DanielGibbs
    Commented Feb 6, 2015 at 5:32
  • \$\begingroup\$ The link for the DIY Tester is dead (failed open): Members Webspace has been retired \$\endgroup\$
    – Martin Zaske
    Commented Mar 18, 2017 at 21:29

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