[ARC5] Forward: Diode Effect in Cap's.

[J. Forster]

Subject:
        Re: [Milsurplus] Re: [The WS No19] Diode Effect in Cap's.
   Date:
        Wed, 6 Oct 2004 20:36:17 -0500
   From:
        aGEnuine Ham <gl4d21a at juno.com>
     To:
        jfor at quik.com
    CC:
        milsurplus at mailman.qth.net, jbbr35487 at blueyonder.co.uk




(Would someone on their list kindly forward this to the Wireless 19 and
ARC-5 groups?  I'm not a subscriber.)

Gents:

There is a long history of old paper capacitors showing non-linearity.  I
became familiar with it in the early '50s, working on TV sets.  One
obvious characteristic was that these exhibited a DC voltage, even after
being discharged multiple times.  The applications where high pulse
voltage was applied seemed to be most likely to fail in this manner.  We
always suspected that some triboelectric effect was taking place, but no
careful scientific investigation was ever pursued.  Also, these were in a
hot environment in a TV chassis, and unlikely to have absorbed
significant moisture.  In any event, a capacitor in an equipment which
had been turned off for several days and which still exhibited several
hundred millivolts to a 20,000 ohm per volt multimeter was obviously in
need of replacement.  I do not recall seeing the effect in mylar
capacitors as much as the old (cheap) paper caps used in B & W TV sets of
the 50s and 60s.

Hope this adds some useful information.

73,
George
W5VPQ