I've got vintage Casio keyboard which upon power on gave scrambled sounds, command states, etc., stuck with it. I've managed to reset old uPD7802 in it with grounding short it's reset pin and everything started to work. After not using it for some months it got scrambled again but this time the reset doesn't work any more. It just changes state in to different scrambled. Found out that it's a common issue with this keyboard.
Data sheet says - "29 RESET (Input, active low) RESET initializes the uPD7801. "
1. am I doing reset the wrong way?
2. did microcode went bad?
3. can some failing discrete element on board prevent normal reset?
Data sheet says - "29 RESET (Input, active low) RESET initializes the uPD7801. "
1. am I doing reset the wrong way?
2. did microcode went bad?
3. can some failing discrete element on board prevent normal reset?