Thanks fellahs, I'll check those suggestions out. And, almo, the original post I had brushes written as 'armature contacts' as I had could not remember for the life of me what thier proper name was...brushes! They all have a lot of life left in them, but I wonder if they're worn to a bad seat- maybe a little mushroomed or slagged edges and hanging up on the three-piece armature contact. They are not your usual spring-loaded graphite pick-up shoes. They seem to be copper rods about 1/8 x 3/8 in size. But you're right. I've changed brush sets before and that can make a big difference.