T.J.

I've worked in the broadcast industry as a sound engineer for 22 yrs, so all I can tell you, is what a professional would do. Pop of the lid of the unit so you can access all moving parts. Clean the heads using low-lint wiper and rubbing alcohol. The brand of wiper commonly used is called "Kimwipes" made by Kimberly-Clark. Drench the wiper with rubbing alcohol and rub gently over the audio head and all guides and spindals. Since you have gone to the trouble of removing the top, now is a good time to de-magnetize the head. Acquire a de-magnetizer (radio shack sells them - cheap) and approach all the moving parts including the tape path and head with the de-magnetizer on. While approaching and moving the de-magnetizere past the parts (don't actually touch the parts) make sure the de-magnetizer remains on. After following the tape path remove the de-magnetizer from the area and turn off. This is a routine that should all be required. If after this, you still have problems, you have worn belts, or some machanical defect, not electronic. Don't use head cleaners of the tape kind! No professional uses them, as they are too abrasive, literally...

Good Luck!