| ampage Tube Amps / Music Electronics |
For current discussions, please visit Music Electronics Forum. |
ampage archive
Vintage threads from the first ten years
| previous: Mr. Droopy-Drawers Your test method will work for a dr... -- 1108829021 |  |
|---|
Re: Testing Filter Caps
 2/20/2005 9:06 AM |
||
| R.G. | Re: Testing Filter Caps
To test for leakage *with high accuracy* requires specialized equipment. For a rough and ready test, all you need is high voltage and a resistor. Hook the cap up to near its specified voltage in series with a resistor; 100K works nicely. DC leakage current is the voltage across the 100K resistor divided by 100K. Capacitor leakage resistance is the inverse ratio of the voltages times the test resistor - i.e., 10V across the 100K with a 400V DC test voltage means 390V dropped across the cap, so the cap's leakage resistance is (390/10)*100K, or 3.9M. Use 1M if you get unusable readings on the 100K. I suppose that you could use a 1M pot and diddle the pot until half the voltage is dropped across the pot; the pot is then equal to the capacitor's parallel leakage resistance. If you can't get half the voltage across the pot, the cap is plenty high resistance / low leakage. You **must** have your cap's leakage resistance be large enough to cause an insignificant heating current (V^2/Rleak) to use it. ...ooops, I did forget the specialized voltmeter... | |
|---|---|---|
| Replies: |
| Mr. Droopy -Drawers Well, I learned a different way to ... -- 2/20/2005 10:28 AM |