1.Power Check Flow
Power switch on
Amber LED ON?
NO
Check S1 and its cable
Check F901
Check the standby Transformer
Check IC1 on the standby board
YES
Hear the relay’s click?
NO
Check the MCU on the keyboard
Check Q91 Q92 and OP91
Check if the main transformers
has been plugged in
YES
+/-70V
un-regulated power supply
is correct?
NO
Press the standby button
A
ELECTRICAL TROUBLESHOOTING GUIDE
5V is Right ?
NO
YES
Check the MCU on the keyboard
Check U84 and Q82
Check the D81
Check F902 and F903
Check the main transformer
Check B603 B604 B703 B704
Check D602 D603 D702 D703
Check PSU PCB
YES
+/-20V
power supply is correct?
NO
Check R648 R649 R748 R749
Check B605 B705
Check IC603 IC604 IC703 IC704
Check the PCB track
YES
+/-18V
power supply is correct?
NO
Check the sockets and plugs
Check 1Q21 1Q22 2Q21 2Q22
YES
3-2
