Casio CTK-691 Service Manual page 18

= Rest of above characters turn on.
A Press "REGISTRATION 4" button.
B Each characters turn in order.
There no lack of dots and characters
12. TUNE check (If no TUNING METER, this check can be skipped)
1 Connect the TUNING METER to the phone jack.
2 Press "8" button.
3 The TUNING METER must indicate "C".
4 Disconnect the TUNING METER from the phone jack.
13. APO check
1 Press "EXIT" button.
* Go out from TEST mode (Power off).
* The keybord turns off after about 2 seconds.
* The LCD turns off.
DIAGNOSTIC PROGRAM IS FINISHED.
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