I am working on this unit which had not operated in some 20 years
according to the previous owner. I changed the belt, oiled the
motors, capstan, and pinch roller. Cleaned and demagnetized the heads.
The right side reel holder had somehow managed to get out of
alignment and I had to loosen the setscrews on it raise it to the
level of the other reel. The unit now plays, but it might still have
these issues:

Hissing. I can hear hissing noise, as you do with a cassette deck
when not using noise reduction, or perhaps a bit louder. Is this
normal? The hissing persists for about 10 seconds after I turn the
unit off. I am playing through a '70s vintage Pioneer, but that is
not the cause. Are these units suppose to be this noisy? This is
definitely not hifi.

Tape tightness. The tape seems awfully tight to me, but I have never
used one of these before. It takes up and rewinds okay.

Alignment. I think the tape on the take up reel is showing a little
crinkling, On the first tape guide before the head, the tape does not
appear to be fully in the slot, rides a little. How can I make sure
that tape alignment is right on? The head adjustment screws are
dabbed with a marking compound and do not appear to have ever been
tampered with.