Missing note.
Contact needs cleaning.
Contact 'boot' distorted and contact rubber not striking onto keybed PCB when key is pressed
Missing octave. Broken or cracked copper track on keybed PCB. Disconnect keybed from instrument and carefully inspect keybed pcb tracks for continuity by using an ohmmeter
Ribbon cable plug not correctly mating into socket
Open circuit in ribbon cable or more often a loose crimp connection within plug on ribbon cable. The micromatch (red) plug crimp connections can become intermittent on the ribbon cable. Carefully check ribbon cable for continuity for each pin using ohmmeter. Attach fine flex wire to meter probes to allow probing.
Each keybed PCB has its own ribbon cable, either 18 pin or 20 pin dependent on the number of keys. Obtain a digital logic probe and use this to check output from instrument pcb to keybed pcb Keybeds are continuously scanned by the instrument pcb when the instrument is powered up so the logic probe must indicate a 'pulse' when touched against the anode (non banded end) of each diode on the keybed pcb. The pulse is rectified by the diode so the cathode (banded end) of the diode must read logic high, is: +5 volts
If any diode does not show the 'pulse' recheck the keybed pcb for track break and trace back to the micromatch (red) socket. The pulse should be seen when probing on the underside trackside of this socket.
Contact needs cleaning.
Contact 'boot' distorted and contact rubber not striking onto keybed PCB when key is pressed
Missing octave. Broken or cracked copper track on keybed PCB. Disconnect keybed from instrument and carefully inspect keybed pcb tracks for continuity by using an ohmmeter
Ribbon cable plug not correctly mating into socket
Open circuit in ribbon cable or more often a loose crimp connection within plug on ribbon cable. The micromatch (red) plug crimp connections can become intermittent on the ribbon cable. Carefully check ribbon cable for continuity for each pin using ohmmeter. Attach fine flex wire to meter probes to allow probing.
Each keybed PCB has its own ribbon cable, either 18 pin or 20 pin dependent on the number of keys. Obtain a digital logic probe and use this to check output from instrument pcb to keybed pcb Keybeds are continuously scanned by the instrument pcb when the instrument is powered up so the logic probe must indicate a 'pulse' when touched against the anode (non banded end) of each diode on the keybed pcb. The pulse is rectified by the diode so the cathode (banded end) of the diode must read logic high, is: +5 volts
If any diode does not show the 'pulse' recheck the keybed pcb for track break and trace back to the micromatch (red) socket. The pulse should be seen when probing on the underside trackside of this socket.