FW: BE-5 - what do the controls on the BE-5 do? Selenium rectifier voltage drop

Mike Langner mlangner at SWCP.COM
Mon Dec 15 20:29:39 EST 2008

-----Original Message-----
From: Mike Langner [mailto:mlangner at swcp.com]
Sent: Monday, December 15, 2008 6:28 PM
Subject: RE: BE-5 - what do the controls on the BE-5 do? Selenium
rectifier voltage drop

>From a web site about British Land Rover charging systems --

Rectifier CAV Type RUS-3
Air cooled three-phase full-wave with selenium elements
Forward resistance 10 ohms
Reverse resistance 1,000 ohms

>From my experience with selenium rectifier battery chargers in the '50's,
this seems about right --

Many of the Heath battery eliminators had absolutely rotten voltage
stability with load changes.  As a result, Heath and many others had a
voltage control, usually a wire-wound power resistor rheostat, to compensate
for load changes so the voltage could be set.  Typical old automobile
broadcast radios were near unchanging loads, no matter where the volume was
set, since the filaments, vibrator loss, etc. comprised nearly all of the

When I was a kid (I'm now 66) fixing TV sets and radios, we'd always replace
selenium rectifiers with the new silicon diodes, and put 27 or so ohms in
series with them to approximate the forward resistance of the selenium
rectifiers.  Of course, they were B+ units -- not single wafer or dual wafer
as usually found in battery eliminators & chargers !

Good luck !


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