Casio CTK-591 Service Manual page 13

10.Remove 13 screws and then the lower case.
Cushion
Note: Tighten the screw with the arrow mark in the figure first when reassembling.
11.Remove 19 screws and then the PCB ASSY (KY1M, KY2M).
12.Remove the rubber keys.
Projection
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.
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