I have been working on restoring 7 different Juno 106s from parts and have two HS 60 module boards that are not working. They both have new voice chips. One does not turn on when a particular module board is used with it. The other does not make any sound but turns on. Any suggestions or people to send to for repair? Just the module boards.
All you can do is check each and every transistor, capacitor, resistor on the board. Then check each wire connector as they break within the connector after being pulled on and off many times. It happens because people just yank on the wires instead of unplugging the cables by grabbing the plug ends.
The very technical and expensive route is to get a logic analyzer and a dedicated ic clamp to fit over the main IC to monitor all the pins for operation and compare it with the other board to see what is working and what isn’t.
The least is use a logic probe to document the bus pins. You will never understand what is happening on the bus pins, but all you want to see is rapid high-low communications. Then look at the other pins for output status comparing both boards.
Also get dedicated video camera system that can magnify pins that can see solder hair causing shorts, or expansion cracks in the pcb traces.