Scrap-n-Repair: Casio CTK-481 Key not working 

This unit was found in the trash area. Tested and one key (E) is not working. Further check found contamination on the PCB pad for Key (E). After cleaning using a contact cleaner and a pin to scratch off the contamination, the unit worked back to normal.
Tools and parts required:
-Philips screwdriver
-Brush for cleaning
-Electronic Contact Cleaner
-Pin to scratch off the contamination
Link for the Disassembly, cleaning, and assembly process: • Casio Electronic Keybo...
Link for the Fading or dark display repair: • Casio Keyboard Fading ...
Disclaimer: Perform this repair at your own risk touching any internal parts can cause an electric shock