How to clean camcorder head?

One or more of my tapes has apparently destroyed the playback of three camcorders in a row, after just minutes of use! If it is oxide contaminating the heads, how can I clean it off? I tried everything on the first camcorder, and it made no difference (which is why I didn't think that was the problem and tried 2 other camcorders!); in fact the tiny heads around the spinnning cylinder are very delicate, and I probably broke them. If something transfers onto the heads so easily, it must be possible to get it off again!?