Well that was fast and easy. Thank goodness. It turns out the culprit was the Astec power supply. It had a dry solder joint on the "DC OK" line. A few drops of fresh solder later and the terminal is good as new (well, as good as any 35-year-old terminal can be, anyway)
While I was inside, I removed a very old but thankfully non-leaky battery. Need to figure out a new battery if I want to preserve settings. If anyone is interested, I did dump the terminal's ROMs while I had it open. They're here: http://www.loomcom.com/3b2/att_4425_rom -Seth -- Seth Morabito s...@loomcom.com