** 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

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

"Phil Allison" wrote in message
...

** 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




Or you can order a blue ESR meter kit from Anatek, solder it together and it
gives you readings and a reference chart to determine good and bad caps.
Much faster and convenient. Plus you have the fun and satisfaction of
building it yourself.

BTW: there not that expensive

Shaun

Shaun wrote:
"Phil Allison" wrote in message
...
** 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




Or you can order a blue ESR meter kit from Anatek, solder it together and it
gives you readings and a reference chart to determine good and bad caps.
Much faster and convenient. Plus you have the fun and satisfaction of
building it yourself.

BTW: there not that expensive

Shaun




I think Phil's point here was if you only wanted to check a couple of
capacitors that you don't need to buy the kit.

Of course if you are servicing machines then an ESR meter is rather
handy...(and we sell the Bob Parker design - Anatek BLUE ESR kit (rather
shameless plug)).

There are also links at the bottom of my original ESR page for
alternative testers including a $0.99 version (yes, that's 99 US cents -
or 98 cents Canadian these days;-).

John :-#)#

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