Casio CTK-900 Service Manual page 15

To remove the key PCB (CSM618T-KY1M, KY2M)
19. Remove 13 screws and the bottom case.
Note: Tighten the screw with the arrow mark in the figure first when reassembling.
20. Remove 19 screws and then the key PCB (CSM618T-KY1M, KY2M).
21. Remove the rubber keys.
Note: Pay attention to the positions of the rubber keys
as one of them has a different length. Match
the projections of the rubber keys with the holes
of the lower case when reassembling.
Projection
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