I bought a used AM/FM/Cassette deck for my car. Unfortunately, the heads, capstans, and pinch rollers were filthy. A cleaning tape barely made a dent in the grime, so I cleaned everything gently with Q-tips and rubbing alcohol. But there is still visible corrosion on the tape head, causing playback to sound muffled (in one direction only; in the other direction, the music sounds fine; it's a reversible deck). I have run the (wet) cleaning tape through the machine about 15 times, to no avail.
Does anyone know of a safe method to remove corrosion from audio cassette tape heads? Not sure if I'm savvy enough to try to remove the tape head from my old player and put it in the new player. Maybe I just need to buy another used deck from a more reputable seller.