Used AC power supply instead of DC. Kawai electronic piano.

[JohnTripperson]

Hi, Everyone.
I have been clever enough to accidentally use AC 12V power supply on Kawai electric piano. It has worked for a few second, made some good noises when I pressed buttons, but then LED screen and lights got dimmer and went out. Later, when I got a correct power supply, it refused to work.
I have popped it open, but cannot see anything burnt out, no fuses.. it looks mint.
Please help by directing me towards what I should be checking first.
Model is Kawai X30 , I can also supply pictures of PCB if needed. There is a stamp on PCB "KES-046"
I am capable in doing stuff.. but this thing has so many bits in it (IC chips).
Thanks, people

[minnie]

Take a multi-meter and see if the plug in transformer is out putting. One lead in the center of the plug in and one on the outside metal. Put the meter on DC.