Yamaha PSR-225GM - No response when depressing keyboard keys
(Colorado Springs, CO, USA)
I have a Yamaha PSR-225GM. It powers up, but I get no response from depressing the keyboard keys. The demo song works, the percussion background works, but nothing that uses the keyboard. Also, the keyboard in the LCD display does not respond when depressing a key or trying the chord accompaniment.
I have purchased the service manual, which is of little help since the only test sequence requires the keyboard to work for it to initiate. I have tighted all of the connectors throughout the unit, particularly those connecting to the keyboard and MKS5 (replacement for the MKS3) circuit board. I did check, and I have +5 volts entering the MKS5 board.