Dear GKR1,

If you can see the head vibrate you need to repair or replace the fan. If you just sort of think it's vibrating, check with your grain focuser. If you can't see nice crisp grain you know you have an issue.

Replacement fans are cheap if you go to an electronics supply house like Digi-Key. Cheaper if you can find one at American Science and Surplus or the like.

Good luck,

Neal Wydra