This may well qualify as a "Lost Cause", but ...

I have 2 dual decks per the subject line. On both, the record drive will
not spin a (good, tested) tape. Same tape works OK in the play-only
drive.

On a workbench with the case open, I push button for play or record or
rewind (forward or backward), the machine appears to do a check for
end-of-tape, clicks, and stops.

I disconnected a motor thinking it might be frozen: it was not.

The behavior it exhibits is identical to what the device is supposed
to do when I, say, tell it to play a tape that is pre-positioned to
end-of-tape. I'm guessing that the problem is with the end-of-tape
sensor.

I am neither expert nor helpless with electronics.

Any hope for repairing such a beast?

TIA,
Puddin'

"Law Without Equity Is No Law At All. It Is A Form Of Jungle Rule."