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?
Best Answer
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.