Well, I had done the mods and was testing it with several batteries around the shack when tragedy struck! I reversed polarized one and zapped something because the PS terminal voltage dropped to about 9-10 volts. So, going into debug mode, I did some poking around and put together a description of the problem to be posted on the Repeater Builder Yahoo Group. Herewith is my initial plea. (Note that I turned these into images to preserve the spacing that the HTML interpreter kills.)
- Repairing Astron 13.8V Linear Power Supplies
- Trouble Shooting an Astron Linear Power Supply
- Crowbar SCR Usage in Astron Linear Regulated Power Supplies
- LM723 Regulator Operation in Astron Linear Power Supplies
The main article was Repairing Astron 13.8V Linear Power Supplies by WA1MIK. It works its way from the wall socket to the binding posts and helps you trouble shoot by symptom. (Mine was "low voltage".) I reduced the main part of the article to a sort of checklist:
Going through the above, I thought that it drove me pretty convincingly to the regulator board as being the problem -- and that everything else was just dandy! Boy what a mistake that was!