I got this enormous Zenith "Video Director" Beta VCR from 1979, model number is VR9000W. It threads tapes really well and the belts are in good shape but for some reason it just will not play. It will make kind of a solenoid click sound and push out a tape guide but then immediately click again and move the tape guide back in, and I don't know why. Could it be a dirty mechanical sensor inside, maybe?

Here's some pics of the unit:

https://i.imgur.com/nbTCQY9.jpg

https://i.imgur.com/UDMT3W6.jpg

https://i.imgur.com/vEvYOgv.jpg

https://i.imgur.com/aJHJPoT.jpg

Make sure you're capstan motor isn't stuck. IIRC it was on mine, but when I did mine I also repaired the Sony badged version, a front load Zenith beta and an older top loading Zenith beta so I could be smearing the memories of 5 consecutive repair jobs together...

Make sure you're capstan motor isn't stuck. IIRC it was on mine, but when I did mine I also repaired the Sony badged version, a front load Zenith beta and an older top loading Zenith beta so I could be smearing the memories of 5 consecutive repair jobs together...

Hmm, it is possible a motor is stuck. Capstan motor being stuck would explain why the tape threads but refuses to play/rewind/fast forward.

Verified nothing is stuck, sprayed down the mechanical switches on the board with contact cleaner, and it still has the same behavior as before. Pressing Play causes a solenoid to engage and push out a tape guide but then said solenoid immediately disengages and the head drum stops turning.

I also notice that trying to play causes the tape to become noticeably less taught, as if the supply reel is supplying more tape but the take-up reel is not taking it up, in addition to the other not playing symptoms.