Re: [CAD_CAM_EDM_DRO] Charging Capacitors

On Fri, Jun 02, 2006 at 03:35:26PM -0000, oldpayphones wrote:

> I have some used 200VDC 5400UF capacitors from a 1970's Bridgeport that
> have been sitting for a couple of years and I was wondering if there is
> a correct procedure for charging them initally. I have had stereo PS
> caps explode after sitting for some time.

Initially, feed the current into them slowly.

My procedure for old AND new large value electrolytics is as follows.

Create a supply at the caps rated voltage and connect the caps to the supply
through a 10k resistor. Eventually, the caps will reach 95 to 98% of the
supply voltage. At that point (and remembering that in your case the caps
now contain a lethal voltage), discharge the cap through a 1K resistor,
measuring the voltage and leaving the resistor in place for at least 30 minutes
after the cap "seems" flat.

Repeat a couple of times.

Replace the 10k charging resistor with a 1K resistor and do this again .. and
again with a 100 ohm resistor and then maybe a 10 ohm resistor.

At this point, you should be done.

If the initial voltage with the 10K resistor never reaches 95% of the supply
voltage, I consider the cap bad. If it only reaches 99% of the supply voltage,
it is questionable but maybe serviceable.


Alan


--

Alan Rothenbush
Academic Computing Services
Simon Fraser University
Burnaby, B.C., Canada


The Spartans do not ask the number of the enemy, only where they are.

Agix of Sparta