you need to check that the pinch rollers are being engaged, you might find that the rollers are just stuck in the down position, if you can remove the whole cassete mech and check the rollers are fitted into the metal chassis correctly. If you are unsure what they look like the are positioned to the left of the play/rec head (or on auto reverse mechs they can be on both sides if you system is fairly new. hope this helps
simon, June 2006
