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12222Re: [midatlanticretro] Capacitor testing (at Bill's?)

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  • B Degnan
    Apr 7, 2009
      Mike,
      If I felt brave I might try to reproduce this. I have a similar power
      supply at work. Maybe I could set one of these up for the weekend of
      the 25th. Anyone else coming?
      Bill

      Mike Loewen wrote:
      > I tore apart my IMSAI in order to remove the four large electrolytic
      > capacitors for testing/reforming. There are two 9500uf-30VDC caps and two
      > 95000uf-15VDC caps. Here's the rig I put together for bringing them back
      > to life:
      >
      > http://sturgeon.css.psu.edu/~mloewen/Oldtech/IMSAI/Reforming-L.jpg
      >
      > I put this together after reading many documents about testing old
      > capacitors. Hidden behind the cap is an 8K power resistor in series with
      > the cap. The small meter is measuring the voltage output from the the
      > power supply (a HP 6443B 0-120VDC/2.5A unit), in this case 25.0 volts.
      > The large meter is measuring the current flowing through the cap, 0.11ma.
      > The voltage across the cap is 24.7V at this point.
      >
      > I started out by raising the voltage by steps, from 3-6-9-12-15-20-25,
      > watching the current and making sure it went no higher than 0.5ma. At
      > each step, I'd let the cap charge up until the current was down to about
      > .05ma then increase the voltage. Once I got to 25.0 volts, I let it sit
      > for a while until the current was down to .03ma.
      >
      > So far I've done one of the 9500uf caps. I'm hoping this procedure is
      > effective. How about it, Dan and the rest of the electronics gurus?
      >
      >
      > Mike Loewen mloewen@...
      > Old Technology http://sturgeon.css.psu.edu/~mloewen/Oldtech/
      >
      >
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