Date: Thu, 10 Oct 2013 10:58:50 -0400
From: "Carl" <km1h@jeremy.mv.com>
To: "Jim Thomson" <jim.thom@telus.net>, <amps@contesting.com>
Subject: Re: [Amps] Alpha PA-76A bleeder/equalizer resistors
Jim, the tolerance is not that critical since there is plenty of voltage
overhead and the original 5% carbons worked for about 35 years.
Standard 5% 3M MOX from Mouser or elsewhere is fine for another 35 years.
All the ones Ive checked are within 2% anyway and modern replacement caps
are listed at 20% but come in around 10% or less at the values used in most
amps.
Carl
KM1H
## I noticed that Rich measures 560 uf HV filter caps read aprx 19% on the
low side for
some reason. I had a batch of GE caps that all read 1800-2300 uf.... but were
stamped
1600 uf..go figure.
## some folks like to operate caps almost at their max V rating. Factor in
caps that
vary a lot of uf between each other, and you might be cutting it close in some
cases.
In these HB HV supplies I build, I never run the caps at more than 70-75% of
their
max V rating, so plenty of headroom.
## Those .2% tolerance resistors cost dick, so I thought I would give em a
try..and
bought 300 of em. It brings the concept of forced V drop across each cap to a
whole new level..as
in they all read identical V drops..right down to 2 x decimal places. All
300 resistors measured the
same, identical 99,980 ohms. I know its overkill, but I sleep better at
night.
Jim VE7RF
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