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Old 19th April 2012, 02:56 PM   #1
kp93300 is offline kp93300  Malaysia
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Default How to test an old 60000uf cap ?

My antique dealer friend gave me these 60 000 uF cap for me to diy.
My cap meter only measure up to 20 K uf.
I intend to use it in a +/_ 22 v dc power supply for the Death Of Zen amp drawing about 3.5 to 4 amp continuously.

How to test these cap before using it ?
I do not have a ESR meter and any simple circuit to test it ?

thanks
kp93300
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Old 19th April 2012, 11:24 PM   #2
Enzo is offline Enzo  United States
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Look up "capacitor forming" and do that to them first. Just to get them capacitating.

If you have a bench power supply use it, otherwise knock together a small power supply making 25-30 volts DC. COnnect a volt meter to the cap, and connect the power supply to the cap. That should charge the cap up to the supply voltage. Now disconnect the power supply from the cap. Monitor the meter to watch what the charge in the cap does. If it slowly drains away, that is a good sign. If it wants to just drop down fast and get out of town, that is no good.

Not very scientific, but no special gear required to perform this admittedly crude test.
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Old 20th April 2012, 12:38 AM   #3
kp93300 is offline kp93300  Malaysia
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Thanks Enzo for a advice .
easy to follow and do.
kp93300
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Old 20th April 2012, 01:35 AM   #4
cbdb is offline cbdb  Canada
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Might be a good idea to put a small resistor between the supply and the cap incase the cap shorts (sometimes happens) The resistance large enough to limit the current to below the max supply current, it will also prevent the large inrush currents that a supply may not like to see.
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Old 20th April 2012, 03:40 AM   #5
Enzo is offline Enzo  United States
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Good idea.
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Old 20th April 2012, 04:22 AM   #6
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If you want to really test it, there's a quick cap bridge that also does losses here that will go to 100,000 uF and just uses a few components. You could also measure the charge time with a known resistor and calculate the value. If you download Visual Analyser (free- Google it), it has a full LCR meter built in. All you need is the right interface to your sound card. Not sure how high it reads. They look like Sangamo. If they're old, check the leakage as well. Chances are they're good.
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Old 20th April 2012, 03:01 PM   #7
kp93300 is offline kp93300  Malaysia
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Default cap bridge

I read the link posted by Conrad.
I will try the circuit .
Please see the attached image .
What does this symbol mean ?
thanks

kp93300
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Old 20th April 2012, 03:51 PM   #8
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Pi
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Old 20th April 2012, 04:32 PM   #9
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Oh my god.
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Old 20th April 2012, 05:11 PM   #10
john65b is online now john65b  United States
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Can't you could put another smaller known capacitance cap less than 20,000uf in series and re-measure total capacitance with your LC Meter??

1/Ct=1/C1 + 1/C2

EDIT - It's been a while, and I think I got that right.
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Last edited by john65b; 20th April 2012 at 05:23 PM.
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