Re: Charging Capacitors

Hello,

A yahoo search of reforming capacitors serves up several useful sites.

Some use a 7W AC nightlight to limit current; thers a 30-50K , 5W
resistor.

I even saw one schematic for a complete capacitor reformer with range
switches, etc.

IOW, The process is fairly well-known and well documented online at
several sites.

Since we're offering some 47Kmfd, 40V computer grade older caps at
cncresource.com so I've recently been reforming caps...

I set one of my DC lab supplies to limit current and start with low
voltage, then turn the voltage up to a bit below the WVDC of the cap
and keep the current low. After an hour or so, I turn the voltage up
to match the WVDC of the cap. You don't want to set the voltage too
high as it will reduce the overall capacitance of the cap.

I've most recently used a 10K resistor to give me a voltage reading
(DMM across the R). If it--the measured voltage-- doesn't start
heading down within the first few minutes, reconsider this cap for
use... (I get away with the smaller R due to current limiting in the
lab supply)

When you do the reforming caps search, you'll also be led to some
sites for purchase and construction of ESR meters. Very worthwhile
instruments to have if you plan to refurbish older electronics, or
sell NOS caps!<G>

Hope this helps, It's actually kinda fun to do. Be careful. Caps can
explode and more likely release unpleasant and potentially harmful
outgassing during the process.

Ballendo


--- In CAD_CAM_EDM_DRO@yahoogroups.com, "oldpayphones" <larry@...>
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.
>
> Thanks,
> Larry Olson
>