I found a Sony SL-HF750 deck today (drawer-loading) at a thrift store today and got it for dirt cheap, but it unsurprisingly has issues.
As I was getting the deck off of the shelf, a customer explained to me that the deck had been there for six months and was originally priced higher until "someone broke it," and now, the deck rewinds when "play" is pushed. His testimony was true, but it seems to be a symptom of a deeper issue. The mechanism does go through the motions to play a tape when the play button is pushed, but only for a second, and then it rewinds instead. Pushing the "fast forward" button results in the mechanism advancing the tape forward for a split second, but then stopping, and at that point, the only function that the deck will allow you to do is rewind.
So, it seems as if this deck has an issue with advancing a tape forward. What could be a cause for this? Since that customer said that "someone broke it," I wonder if there was something in the mechanism that was put out of whack when it was "broken."

Sounds kind-of like the tape end sensor isn't working, erroneously signalling the system controller that it's at the end of the tape when it isn't and going into auto rewind. Time to pull out the service manual and do some troubleshooting.

Sounds kind-of like the tape end sensor isn't working, erroneously signalling the system controller that it's at the end of the tape when it isn't and going into auto rewind. Time to pull out the service manual and do some troubleshooting.
That would make the most sense. The deck appears to have the mechanical capability to play and fast-forward tapes, since playing and fast-forward works for a split second, but the deck seems to stop itself from doing that.

The unit could have had a tape jam, that customer yanked the tape out and busted something. There could possibly be two problems existing. Hopefully, parts are still available.