Casio AP-20 Service Manual page 9

7. Disassembling keyboard PCBs
7-1. Turn round the keyboard unit to face the PCB
up.
7-2. Disconnect the connector at the middle of
keyboard.
7-3. Remove screws on the keyboard PCBs.
8. Replacing the main PCB
Note: The main PCB contains a lithium battery for memory back-up. Please remove the jumper
before replacing the PCB. And make sure that the jumper is reset on new main PCB after
replacing the PCB. Because no jumper is set on a spare part of the main PCB.
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Jumper