Here's a rare tape mechanism from a Sony TC-K777ESii cassette deck. I overhauled this unit about four years ago and it has been working well since.  Replaced the left side pinch roller, belts and rubber rollers in the reel assembly.  Original laseramorphous heads are still in good shape.  Last I checked, wow and flutter was running about 0.03 - 0.04% and tape speed was good.  Rewind and FF are fast and quiet. Cassette lamp was replaced with LED light of the same voltage rating as the original.  One issue is that the tape counter is running slow. Not sure if this is due to the rotation detection circuit or something with the hubs.  A nice unit all-in-all though.  It sounded great in my setup.  

These units have an industrial build quality and I have never seen one fail after working on about 15-20 of them. They are extremely reliable.  Although this mechanism is very similar to the 777ES unit, I don't think it's compatible with that model due to the different wiring harness.