[450] Astron RS-50A Repair

john.foege at gmail.com john.foege at gmail.com
Thu Aug 27 21:38:15 EDT 2009

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
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