Hi, thank you for contacting JustAnswer.com. My name is Russell. I will do my best to provide the right answer to your question.
That most likely is owing to amplifier failure.
It might possibly be related to a blown fuse in the audio circuits, or shorted speaker outputs causing a blown fuse - check the speaker wiring, if any has been hooked up or if any is visible.
The only thing close to a schematic that I could find was this:
I would advise you to seek a qualified Suzuki piano servicer in your region. If you will indicate your region (by zip code) I will research contact information for several if I can find any in your region.
If you would prefer that I advise you further, I will do so as well as possible.
Do you intend to disassemble the piano yourself?
Do you have electronics tools, and experience with electronics repairs?
Neither did I find any Suzuki manuals for repair or service - except for Suzuki motorcycles and the like.
Since I'm admittedly not tops at finding schematics, and since you need one distinctly much, I have Opted Out, in favor of another Expert with a library of schematics or good schematic-finding skills.
Note that Opting Out does not cut off communication, and I can still see and respond to your further postings as needed. But it does open the case to other Experts.