Yamaha p80 starts ok but after some seconds clicks with no sound

What electronic component may cause clicking to turn off the P80 some seconds after turned on? During the time the unit is turned on everything functions well, but some seconds later a click near the jack board is heard consequently turning off the tempo/other value display and leaving no sound when any key is pressed.

The click is a relay on the jack board that is turning on/off the speakers. The signal (MUTE) that holds the relay on the on position (relay engaged) comes from the main CPU on the DM board. If the CPU finds an error or fails that MUTE signal drops and hence the relay dis-engages.
So - problem could be anything from power issues, Power adapter and various 5VDC and 3.3VDC regulators on the DM board, to bad memory or bad CPU to corrosion on the board(s) somewhere
Unless you are well versed in electronics you need to see a tech with it!