I have a Korg Triton Pro that I am repairing. At power on, the touchscreen will flash blue, and then go black, and not work. With a working KLM 2091 power inverter board, and a working touchscreen, the problem still persists - a black, non working touchscreen. Other red lights work, and the screen will beep when touched. What causes this problem???
If there is no audio coming out then i would start with checking the power supply output voltages. You might have a bad cap or component that shorts out after startup hence powers down other stuff. The power supply has HIGH VOLTAGE exposed parts so i would be very careful around it.