Yamaha PSR S770 Won't turn off after Powering On

Good morning my good friends, how are you all doing at this pandemic period. I wish you all safety and good health. Amen.

Please I have a PSR S770, the issue is it won’t power off each time i power it on, unless I remove the adaptor for it to turn off.

Please buddies, what do you think could be the problem and possibly solution to it?

Am very open to your professional advice now. Thanks, I’m most grateful.

Best regards.
Be safe.

Probably the power switch. You can try cleaning it with some contact cleaner, deoxit etc. But it is a component that gets a lot of use.

1 Like

Alright, I will try this. Thanks buddy.

Very much doubt this to be caused by the power switch

PSR-S770%20Power%20Switch

If you look at the 2nd pic and follow the yellow/red line - the switch just makes GND contact that is all.

1st pic - follow the red line and the switch GND just turns on the FT100 FET and enables +16V to go through.

Now it gets tricky - PWSO and PWSI go directly tp the CPU. As soon as power is on and the CPU is running it holds PWSO high - hence FT100 FET stays on (green line).

Next time the power switch is depressed follow the blue line … PWSI gets sent to the CPU and it then de-asserts PWSO and the unit powers off.

Therefore - my guess would be either the CPU is not doing what it should --> do a FACTORY RESET maybe - or, more likely, bad contact of sorts from D102 via PWSI to CPU (it not seeing the off command) …