Rod,
You may have missed the other emails on this. I have isolated the fault to
the motor control board.
I assume you swapped the boards indivdually, so you know the fault is o
nthe motor driver PCB, not the main logic board.
I have tested the power transistors on the board, although it seems that I
have not tested some of them in the correct manner, will try to do that
today. There does not appear to be a printset available for this board,
although it is small enough that I may be able to draw it out for someone
who has the electronics knowledge to direct me what to test.
When I ahve some spare time I'll dig out an RD53 and see if I can roughly
figure out what is going on.
-tony