Ralph Mowery wrote:

Cecil Moore wrote:

Dave wrote:
what does the voltage read when it is turned on? an rs-20a is probably
not so old that caps would go bad, and the low voltage left over when
you
turn it off probably means the caps are holding a charge.

Or if anything is externally connected to the power
supply, the left over low voltage can be coming from
that connected device. I have my RS-20 connected to
a deep discharge marine battery. If I forget to
disconnect the battery from the power supply when
I power down the supply, the meter on the supply
displays the battery voltage. I'm told that can
damage the regulator within the supply but that
has never happened to me.
--
73, Cecil http://www.w5dxp.com

I have not done the modification to one, but here is a modification for
the
floating batteries.

http://www.repeater-builder.com/astr...rsbattmod.html

http://www.repeater-builder.com/astr...n-rsbatmod.jpg

There is much info on the Astrom supplies he

http://www.repeater-builder.com/astr...ron-index.html


Thanks Ralph - very interesting reading. My mid 80s vintage RS20A seems to
be falling out of regulation under the ~15A load of my HF xcvr during xmit.
Fortunately for me, I homebrewed a PS from an article titled "An RF-Proof
30-Amp Supply" (ARRL Handbook, 1988-89) that works much better. The output
doesn't start to fall off until the load approaches 27A (using 4 x 2N3771s).
With the exception of the outer cabinet itself, it's entirely homebrew...
fabricated the chassis, made my own photo-etched PCB, and rewound a 750VA
transformer.
73,
Bryan WA7PRC