Thanks Bojan,
Just finished 'exercising' the gearbox with the help of a pair of pliers on the shaft turning the gears fast back and forth and succeeded in freeing up the gears to the stage where I could turn it by hand and, I gained two turns of the stepper motor shaft per minute. Great, now I might not need a replacement gearbox. But will now know where to go to get a one. And, no sign of any stalling of the motor.
Ken
