Casio manufactures many models of digital keyboards, such as the Privia. Like a piano, the Privia is controlled via the keys on the front of the unit. Over time it is possible for these keys to become stuck or damaged. In these instances, you can replace the key. This will involve some disassembly of the unit but it can be completed quickly.
Power off your Casio keyboard and remove all cables from the rear of the unit.
Turn the unit upside down and remove all screws from the bottom of the synthesizer.
Turn the unit right side up and remove all screws from the sides and corners of the housing.
Lift the housing up to expose the internal workings of the keyboard. Locate the key you wish to replace.
Remove all screws on the key assembly and remove the key assembly from the unit. The key will be connected to a bushing, which in turn connects to the motherboard.
Remove the screws on the bushing and remove the key from the bushing.
Insert the new key into the bushing, making sure the end of the key with the "bubbles" goes in first. These bubbles at the end of the key are actually the contacts that connect to the motherboard.
Fit the key assembly in the keyboard and replace all screws on the bushing and key assembly.
Replace the keyboard housing and screws.