Yes...I knew about all the Record switches...they were all lighting up when engaged, etc.
BUT I HAVE GOOD NEWS!!!
I removed the head block, and ran some continuity tests on the heads, and also checked some of the wiring on the head PCB and on down to the main REC AMP PCB...and during that process, something shifted, and now I can record on both channels!!!
I will still need to locate the cause...though it's looking more and more like just a bad connection or a cold/intermittent solder joint along the path I was checking...though it could also be somewhere else, since I had to move the PCBs around to get inside, and something moved somewhere.
At least I think I've ruled out bad heads or bad switches or blown electronics...now I just have to find the bad connection and fix it so it stay good.
But I made it this far, though I got a migraine staring at the schematics...they could have made them even smaller! ;-)
Now for the next step?
I'm going to throw on a reel of tape, put it in Record, and them gently tap/move/pull on some of the wires/connections while watching the Left VU meter.
Hopefully, I will find the bad connection easy enough...and HEY, so far I haven't broken anything during the process or lost any of the screws! (I'm going to keep my fingers crossed.) :-D
I should have it sorted out and all back together sometime tomorrow afternoon and I hope to be recording some music by the early evening.
OK...so a couple of days troubleshooting down the drain?but it should be an easy fix in the end, and best of all, no need to take it in for major service, though I still have to check the electronics/calibration, and I don?t have a test tape for it yet, so I?m hoping everything is pretty much spot on and I won?t need to get that serviced, though I won?t care if it has to go in for that, at least the deck is not broken in a bad way like I first thought.
When I locate the source of the problem...I will post back for sure.