In message , The Natural Philosopher
writes
On 25/03/17 18:51, Tim Lamb wrote:
I've given the com a clean up with emery cloth and raked out the
segments. Thorough blow through with compressed air and I'll see what
new brushes achieve.


if you have it out check resistance to the frame/armature stampings
from the commutator segments. Its rare for arcing to blow an RCD unless
you have **** loads of electronics (RFI caps) between live and earth in
the house and a rather high impedance supply.

Open circuit on 20 meg range between frame and all comm segments.

Fair bit of carbon dust came out with the compressed air.


--
Tim Lamb