Here are some images taken from the [https://elektrotanya.com/yamaha_dgx-640.pdf/download.html|service manual] for the keyboard which may help to find the problem. The manual shows how to dis-assemble the keyboard so that access to the boards, connectors etc, is possible. Be patient if you go to download the manual as it takes a little while to go from processing to download, once you have passed the recaptcha test and clicked on go to download, below the document preview box.
-
The C and the F# notes share the same two wires through the key board keys and back to the DM processor board.
+
The C and the F# notes share the same two wires through the keyboard keys and back to the DM processor board.
See the composite image below that shows the two wires where they leave the keys on the GHL88M board Connector 2 wires n16 and n26 to go to DM board Connector 6 wires n16 and n26 to get the power and also to connect to the CPU.
The n16 power feed is via resistor R102 and the n26 power feed is via R129 on the DM board.
-
You need to check that the +50V is on both resistors and that the connectors are plugged in securely.
+
You need to check that the +50V is on both resistors and that the connectors are plugged in securely and that the wires are terminated OK on the connector etc.
-
I have only shown the relevant sections of the circuit for the keys and also where the GHL88M is in relation to the other keys, but since the power leaves the DM board and then gets to the GHL88M board 1st before it multiples to the other keys and as all the C and F# notes are affected these are the most likely trouble spots.
+
I have only shown the relevant sections of the circuit for the keys (notes? - I’m not musical at all) and also where the GHL88M is in relation to the other sections, but since the power leaves the DM board and then gets to the GHL88M board 1st before it multiples to the other boards/keys and as all the C and F# notes are affected these are the most likely trouble spots.
Hi @hall_pass_please,
Here are some images taken from the [https://elektrotanya.com/yamaha_dgx-640.pdf/download.html|service manual] for the keyboard which may help to find the problem. The manual shows how to dis-assemble the keyboard so that access to the boards, connectors etc, is possible. Be patient if you go to download the manual as it takes a little while to go from processing to download, once you have passed the recaptcha test and clicked on go to download, below the document preview box.
The C and the F# notes share the same two wires through the key board keys and back to the DM processor board.
See the composite image below that shows the two wires where they leave the keys on the GHL88M board Connector 2 wires n16 and n26 to go to DM board Connector 6 wires n16 and n26 to get the power and also to connect to the CPU.
The n16 power feed is via resistor R102 and the n26 power feed is via R129 on the DM board.
You need to check that the +50V is on both resistors and that the connectors are plugged in securely.
I have only shown the relevant sections of the circuit for the keys and also where the GHL88M is in relation to the other keys, but since the power leaves the DM board and then gets to the GHL88M board 1st before it multiples to the other keys and as all the C and F# notes are affected these are the most likely trouble spots.
Hopefully a start.
[image|2138639]
[image|2138638]
(click on images to enlarge for better viewing)