OK. As far as I can tell all voltages above look good.
I tried tracing the buttons from the Main Control board and they go through some transistors and out to Connector J to the Capstan Motor Control board.
They then go to the Capstan Block.
This may be hard to read, but I'll put the schematic in for reference.
See if you can locate the Capstan Motor Control board and Connector J (outlined in green below) and pointed to with purple arrow.
I tried tracing the buttons from the Main Control board and they go through some transistors and out to Connector J to the Capstan Motor Control board.
They then go to the Capstan Block.
This may be hard to read, but I'll put the schematic in for reference.
See if you can locate the Capstan Motor Control board and Connector J (outlined in green below) and pointed to with purple arrow.
- Measure the voltage on J pin 2 when the STOP button is pressed,
- Next, when the FF button is pressed,
- and when the REW button is pressed.