I have a Yamaha DX100. It does not turn on, half of the black squares appear on the display and the red LED lights up. I checked the voltages, they are all O.K. The processor power supply is also OK. I replaced the electrolytic capacitors on the power regulators. I corrected all the solders on the integrated circuits. No changes. It still won’t start. Do you have any other ideas what could be wrong with this instrument?
Have you got an oscilloscope … and have you got the circuit diagram ?
You need to go way back to the fundamentals … have you got a clock, have you got a 1/2 clock, have you got a 1/8 clock, is the Reset circuit working etc etc etc ?!