Check U34 and any components nearby for bad soldering, open/short circuit, damage, etc.
Remove F/W (U25) and replace it with a working No F/W, check if the machine will function normally. Yes Remove the top cover, remove the panel; check if there�s any signal output on pin15, 16 of U1 on the front board(also check for bad soldering)
Replace main board
Check SW1~SW7 and any components nearby for bad soldering, open/short circuit, damage, etc.
Check the 12pin cable that connects the front board No with the main board, check if the cable is properly connected. Yes Check the 12pin cable that connects the front board with the main board, check if the cable is properly connected.
Replace front board
Use the oscillator or multimeter to check if the voltage between p10 No and GND of JP6 on the main board �27V and also check if the voltage between pin2 and GND 5V
