I would be looking at the e unit. Power should go in the eunit on the black wire, then out to the armature on the yellow wire, back in on the blue wire, then out to the field on the green wire. Check to verify that these connections are being made. E unit fingers are very fragile and can get bent so they are not touching the drum. You should be able to light a lamp between the green wire and the frame every other cycle of the eunit.
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