[450] Astron RS-50A Repair

David McKenzie kb1fsy at vhfwiki.com
Fri Aug 28 13:56:11 EDT 2009

hip hip

On Thu, Aug 27, 2009 at 9:38 PM, <john.foege at gmail.com> wrote:

> I'd like to share with you all how amazing lighting is. What I had expected
> was the surge traveled down the dog fence wire and jumped into the RG-8 on
> the ground over the top of the buried loop. Yes even in the wet ground in a
> huge copper loop, it created enough to blast a pinhole discharge through the
> RG-8s dielectric and down into the ICOMs HF antenna connector.
> What I noticed today when I shipped the ICOM out for service, was that it
> also jumped out of a screw on the ICOMs top chassis into the Mirage 80 watt
> brick amp that was sitting near it -- torching little black marks everywhere
> it went.
> It also managed, as I looked more carefully at my gear to totally kill my
> Astron!!! Not cool!!
> So, being ever hopeful, I thought that, most likely, everything in the
> Astron likely survived except the LM723 regulator chip. I called up Cables
> and Connectors, and they had one left in stock. An NTE923, which is a pin
> compatible replacement.
> I grabbed it and dropped it in. Voila! The Astron fired back up. I adjusted
> the voltage trim pot to get it up to 13.8V.
> I wasn't satisfied, however, with just seeing that it fires up and reads
> 13.8V. I wanted to test it under a full load. Not having a 0.3 ohm 550 watt
> resistor handy, I racked my brain all day, and even tried to build a
> salt-water resistor, which worked only marginally well.
> Finally, my dad and I came up with the idea of using a transformer as a
> ballast, and he suggested the 1kW microwave xformers I have in the basement.
> I wired up the Astron to the primary coil as a big fat wirewound resistor
> and cranked her up. She comes up at 40 Amps 13.8V and is humming along fine.
> I'm super happy about this and thought I'd share!! In the future, if your
> Astron gets spanked by lighting, try the LM723 first!
> 73s John
> Sent via BlackBerry by AT&T
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