Hi checkin (BTW, we use our real names here, please read Forum Rules),
Check/clean all switches and pots.
You can narrow things down if your machine has 3 heads. If so, see if it''s passing signal when switched to source and tape.
If it's out on source, it's probably not your heads.
If it's only on Tape, it's could be a problem with a connection between the head and the output amp.
If possible, find a service manual before you dig into the guts.