Ok, update! Leaving it off for a few hours + another rest (The manual details a "jumper" CPU reset seemed to clear it up). So, it's working FB now :) Seems like I know what happened. I think the serial port for this machine has a really, really low "off" state (12V). This biased the transistor, I think, and sent the wrong polarity to the PTT of the thing.. At least, I think that's what happened.