On 2018-09-08 18:27, Bob Engelhardt wrote:
On 9/7/2018 6:20 PM, Bob Engelhardt wrote: [...]
The windings at the back of the commutator are wrapped in string &
coated. I'm thinking that I can cut back the string & get at the
winding.

With a small bit in a Dremel I excavated behind the segment, down to
its connecting wire. There was no continuity from that wire to
other segments! Then I noticed what had been staring me in the face
all along - the connecting wire exposed and broken:
https://imgur.com/a/jhIcgqf

Its connection to the segment also came loose, so I soldered in a
jumper: https://imgur.com/a/yiBcCit

It surprised me that the original connecting wire was steel. I
don't know why steel would be used, but it made soldering difficult.

Congrats! Now that the connection is done, make sure to touch up the
worked area with epoxy to protect it from vibration and from being
sandblasted. Since it's going back into a drill and drilling dust is
highly abrasive at typical rotor velocities, neither the wire nor the
soldering should be exposed. The epoxy coating should be made smooth so
that the "bump" over the rework does not stick out too much into the air
and dust stream. When applying epoxy, try not to leave any unfilled air
pockets underneath as far as practical.