Sony SD204

Yesterday I went to use this, my old cassette recorder/player, only to find that when I used rewind, it forward wound instead. Today it is in pieces for me to try and find the fault. It is very old and I have changed some of the circuit design so I am very aware of the electronics, but I have never had a mechanical problem with it and I am finding great difficulty in sorting out what has gone wrong; hence the blip.