Caught or broken ribbon of cassette

Make sure your ribbon is tight going in. Look at the bottom of the tape, and spin the two winding wheels to remove any slack. Next, I would get yourself a wet head cleaner kit from Radio Shack. Or, get the solvent cleaner in a can, and some long swabs to clean the heads, pinch roller and clean the tape path spindles. Some where in there, you have some debree. Note: this is as far as one would be able to go before going to the repair shop.