"Iirc, you can remove the wire from TB11-1 (#29) to verify the card output to the potentiometer. This is around 8vdc."
I'll do that this morning and report results.

TB11-5 and TB11-6 were measured independently with the F-R control lever first in forward, then in the reverse position. When 5 measured 11.5, 6 measured almost zero and vice-versa.