Hello Everybody,
This is my first post on here so please be nice

I have a Yamaha PSR-31 keyboard and until a couple of days ago, it was working fine. Now, when I turn it on, nothing happens. No LED and no sound when I press the keys. I have tested the power supply with a multimeter and it is absolutely fine. I then tested the main board inside the keyboard and there seems to be 13v (the power supply is 12v) everywhere. Even across the LED and in signal cables going to the sound chip. The capacitors closest to the power jack charge to ~5v and then discharge to 0v and stay there. I'm including a copy of the schematics that I obtained directly from Yamaha in the hopes that it will help you to help me.

https://www.dropbox.com/s/50senlfd7281yfz/PSR-31_C.tiff

 

I´d start with a meter and check the supply in the lower right corner and check if the voltages fit the labeled points.

 

What's the voltage between the collector to gnd and emitter to gnd of TR2 2SD880?

Did you check the power switch? Is it a slide switch with spring contact sliding on the PCB? It can get dirty sometimes and makes bad contact.

Where is the capacitor did you measure 5V and going to zero? There are at least 8 caps around that area....

Allen

 

Thank you both for trying to help but it seems the problem was with the ancient power supply I was using. It died during a test and after replacing it, the keyboard works fine.

I have opened a new topic for my Creative Inspire T3030 Speakers here.