On Jan 24, 11:14*pm, "Phil Allison" wrote:
*** Anyone who needs to check the ESR of a few electros can lash up a test
rig in seconds *- *all you need is a bench audio generator and a basic scope
or CRO as poms and Aussies call them.

*Set the audio gen to about 100kHz (sine wave) use full level and connect
the output across the electro under test *- *then connect the scope probes
direct to the same cap, not the generator *- *this is important.

You should see a small voltage at 100kHz on the scope - say 2 to 100mV rms.

*By comparison with known good electros of similar ratings, one can note the
residual voltages and determine if a given electro is OK.

If you put a 1 ohm test load on the audio gen - *you can easily find the
output current and then use the voltage readings on the scope to get actual
ESR values for electros.

Tests can be done while caps are still in circuit *- *but be careful to make
sure they are fully discharged first !!!

.... *Phil

I didn't notice mention of any series resistor, and I have generators
of both 50 ohm and 600 ohm
output, but I guess if it doesn't blow out, it will be OK. !! Good
tip.

greg