I cannot find a circuit for a Yamaha P-45 but have found the service manual for a Yamaha P45-B which hopefully will be close enough to be of some help.
To download the file click on the “I am not a robot” checkbox and then select download. Be patient it takes a little while to find the file.
I don’t know about notes in music but looking at the circuit it appears that a +3.3V supply is fed to each note in the scale and when a key is pressed this voltage changes and the change is detected by the CPU and the appropriate note is played.
Since only the first 4 lower D notes don’t work it may be that there is a break in the wiring multiple or a loose connector to the section of the keyboard.
Check that the harness plugs between the DM board Connector 201 and the GHL88M board Connector 2 and the GHL88M board Connector 1 and the GHL88L board Connector 1 are securely connected and that there is +3.3V appearing on the appropriate pins as shown below The GHL88L, M and H boards may be directly below the keys
Here are some images where I have shown the location of the power supply circuit for the D notes.
click on images to enlarge for better viewing.
The power for the D notes is on wire N12
and leaves the DM board on Connector 201 pin 27
where it comes in on GHL88M (M for middle?) board Connector 2 pin 2 to feed the middle numbered D notes (D2-D4) and multipled to GHL88H Connector 3 pin 2 to feed the higher numbered D notes (D5-D6) as well as GHL88M board Connector 1 pin 17
where it connects to GHL88L (L for left?) board Connector 1 pin 2 to feed the lower numbered D (D0-D1) notes
War diese Antwort hilfreich?