Testing capacitors in circuit - Printable Version

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Testing capacitors in circuit - bridkarl - 03-26-2024

I think the answer is no, but is there any way to test capacitors without unsoldering them?  I can check with an ohmmeter for continuity I guess as a basic test.

I have a radio with what looks like a good set of Sprague caps. I plan to just leave them alone until I have an identified problem.  I need to replace these obviously physically bad electrolytic caps.

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RE: Testing capacitors in circuit - RodB - 03-26-2024

There are circumstances where you would be able to test a cap in circuit. You need to have one end out of the circuit otherwise other components will interact and make the measurement unreliable. If it is connected as the only component to a tube element then you could run a test on it. If the cap has a high DC voltage on one end it should block the DC from passing through, so you can measure the DC voltage on both sides to check if it is leaking.

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RE: Testing capacitors in circuit - David - 03-26-2024

Looking at the resistors would not be unexpected that many are high so test the caps after removing one end of a resistor. David

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RE: Testing capacitors in circuit - morzh - 03-26-2024

More or less what Rod said.

If your cap connects to a tube's pin (grid, plate) without anything else (e.g. a resistor), then, especially with the tube out, the cap can be tested in circuit.
Otherwise lift one pin up.

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