I have a small vacuum cleaner motor, single-phase, AC commutator motor, 120V, 4 A Max., series wired (all coils, brushes connected in series), no start capacitor, two-pole field stator, with thermal fuse in series with circuit and taped against one of the field coils.
My issue is this: Originally not working/no power. I tracked down the problem to a blown thermal fuse. In the process of removal, I damaged one of the stator pole coils (they are apparently aluminum wire, so more fragile than copper). I decided to remove all the aluminum coil wiring and rewind both field stator coils with enameled copper magnet wire. After re-winding the coils and putting the armature/stator assembly back together, I tested it before complete re-assembly by using wired jumper/test clips to join unconnected wiring points.
It started and ran well--running it for 2 hours as a test. When I went to re-assemble, and soldering the wires to connect, I energized the motor again, but it moved only a small fraction of a rotation, then froze in place and sat there humming. There was no physical restriction on rotation-- it always turned smoothly by hand. I checked and rechecked various aspects of the motor a number times, such as brushes, commutator, connections but could find no obvious reason or change from when it ran upon first trial.
Can anyone offer any possible reasons why motor not now working when worked on first power up? What am I missing?