I got given this and on testing it worked in Playback /FF/RW mode at least for a while. It has obviously been somewhere very damp judging by all the rust.  After taking it apart to clean the very noisy headphone slider and re-assembling, It did not work. Having checked I found one of the voltage regulators (-15V) had gone and by renewing it and the leaky cap associated near the fuse, that is restored OK.

Next the fuse on the uP board was blown, so I replaced all the electrolyitic caps for luck on the board, replaced fuse and it stayed intact. Lights were on, VU meters full on, no response from the keypad. Measuring at the fuse, I see 12V, but next to it a 6.2V Zener, which on inspection is physically broken. Replaced 6.2V zener and fuse has gone. I presume the VCC pin 40 is looking for 5V not 12 so maybe its gone bang?

Any ideas what to do!!

Thanks Peter