hifi engine

Marantz PM 8004

Hallo everybody, \

Ive got a PM 8004 of wich the selector indication (and switch) is not working, I checked various voltages and I noticed the 18 volt rail to be 15.6 Volt and also I don't see any Data and clock coming from the uProcessor.
Funny thing is that the amplifier has been 'repaired ' a number of times for the same problem but the same fault has returned every time.
Owner is totally sick of the thing and asked me to look at it for the last time.
With greetings