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Brad H
 
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So I can parallel either diodes alone, or rectifier blocks to get
increased current capability? I understand about the cascade failure
if one should go. Since the charger has about 6 taps on the primary,
for increasing rate of charge (simply higher voltages) can't one just
select a lower setting and ignore the voltage drop the old selenium
rectifier had? I'm not quite sure I understand how the old unit acted
as a voltage regulator. Is that just because it had resistance/voltage
drop that modern diodes don't have?
The old amp meter has a shunt of about 1/2" wide copper about
1/16" thick, so it was just a milliamp meter with a calibrated scale.
I suppose I could hook up something like an old toaster with a known dc
resistance to calibrate a surplus one if I wished.
Alternator diodes are a good idea. They might be rated high enough
to do the job individually, without paralleling them. I looked at some
online places and didn't see much over 50A with a quick peek, hence the
first post here.
The old unit has the selenium stack under a fan, so it should be
easy to mount the new rectifier on a surplus heat sink and place it in
the air flow.
This was a curb find, so at a minimum its a good high current/low
voltage ac transformer.