The patient is a JVC BR-S611U. This is an old professional SVHS edit
VCR. It loads okay, and positions the tape in the "half loaded"
position. No response to play, fast forward, or rewind. On eject, the
tape is not retracted back into the cassette. Using an empty cassette
shell, I can see that there's never any movement of the supply or
take-up reels.

Any suggestions on how to proceed? This went to a shop, which claimed
there was a power supply problem and the deck was not worth repairing.
The owner is a friend of mine and asked me to have a look at it.