[pmrid (Peter)]

I'm trying to put my old EQ6 back into useful service as a stand-by. But have been having endless difficulty with one of the motors - or it may be in the circuit board - or even so odd combination of both.
I can absolutely eliminate gears, worms, and any sort of purely mechanical/alignment issue - because this problem occurs even when the mount is disassembled.
When the motors are connected, power applied and the usual introductory Synscan stuff is out of the way, and I send a slew command to the RA motor, the motor rattles loudly but does not spin its gears. When I swap the RA and Dec motors on the circuit board both motors run smoothly and with no protests. When I sawp them back, the RA rattles again and goes nowhere.
The motor seems OK because it runs fine when on the other connection. The RA connection seems fine because it runs the Dec motor just fine.
I am at my wits end trying to unravel this riddle. Any suggestions would be welcome.

Peter