The story of this Sony WM-FS495. The main board was badly corroded by battery fluid and I don't think it's worth repairing. Fortunately the motor still runs so I turned it into a device that can extend other players' life and save some tapes. Basically I removed the top plate covering the head and the head assembly itself. Now with the tape running, I can use a Q-tip dampened with denatured alcohol to remove mold on a tape. It has worked very well for me. I can also use it to fast forward and backward an old tape (to loosen it up) before I play it. Unfortunately I can't make it sing anymore, but it can do some tasks nicely in silence.
honestly it running at all after getting royally screwed by a leaking battery is a miracle in itself. if it somehow still runs and plays a tape more power to it ive seen some battery acid corrosion so bad the board was barely even suitable for parts, let alone the thing somehow still powering up lol
