Careful disassembly of the motor revealed that one of the brushes was somehow skewed in it's slot and was crossconnecting the commutator slots. How this happened is beyond me, as I have taken many of these motors apart and not seen this before. Be aware that disassembly is NOT for the faint of heart as getting the springs and the brushes is tricky, but using sewing needles to hold the springs back while reassembly is a neat trick. Pulling the needles out after the brushes and holders are back into position is the secret for me. A LOT of the pieces of these slightly different models of the motors are interchangeable, but not all. Many of the gearboxes use the same frames with only slight changes in gears, so changing the ratios is often possible if you have a selection of them. They often come on sale on the auction site in batches so for hobbyists, picking up a few occasionally is a good idea.
Mike VE3EQP .....>
