The drive logic is set up for manual loading (or when a drive loses power with tape wound on the take-up reel) where it will dump the tape into the vacuum columns and then begin seeking the BOT marker.
RESULTS OF ATTEMPT
Threading the tape through the transport is annoying since the drive is really designed for autoloading, but I was able to get it through and wound around the take-up reel. In fact, as I wound the tape I saw the Load Point light flick on, which helps validate that the Beginning of Tape sensor and logic works properly.
However, when I hit the Load button, the top reel allowed its tape to buckle out of the entry slot in the tape transport and not load down into the upper vacuum column. Sigh. I will need to do more tape path and loading debugging. Sure wish I had the clear plastic alternate cover for the transport chamber.
DISCOVERED BAD CONTROL LOGIC PCB FOR DRIVE B
My recent tests with drive B were done with two PCBs I had swapped in from drive A - the control logic PCB and the reel pre-amplifier board. Since I was going to move back to drive A for the manual loading test I described above, I wanted to move those boards back where they belonged.
When I put the original two boards into drive B, the place they sat when I acquired the drives, at power-up the supply reel began rotating slowly clockwise. This occurred without having pushed the Load button at all.
Through process of elimination I determined that the Control Logic Board is the one that is malfunctioning. None of the LEDs light up on the board. I have the board pulled out and will have to do a very careful examination as the first step in diagnosing this problem.