Re: New use for my old FM transmitter
If your cassette player plays fine with regular cassette tapes, then the adapter is likely defective/ broken. It could be a misaligned head (not precisely aligning with the cassette head), loose wiring etc.
I've been using a cassette adapter for years on my older car, and it has worked great. I used to have an FM transmitter, aside from regular interference which degrades sound quality....during travel , some strong stations well interfere with the tuned frequency forcing you to change frequency.