With reference to the attached schematic, I would proceed by first connecting the stalk and measuring the voltage at pin 2 of the PIC, IC4, as the controls were manipulated.
We have 5.03V here. Fiddling with the stalk (tip to collar trick) doesn't change anything.
If you don't get any voltage there, or it doesn't change, check the output of IC3 pin 1, the LM258. Also check it actually IS a 258
Again, 5.0V on idle. Pressing a button shows around 0.5V briefly (< 0.5 sec) and then 0.89V while the button is held down. As soon as the button is let go, its back to 5.0V
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