You need the Backglass off and the front panel down to observe what "okorange" has stated above.
If "B" is rotating properly, it should be resting in the detent.
If it is, the fingers on that assembly might be dirty or rusty. You may have to clean them to get a
clean connection to light the lamps.
Or it could be the switch contacts in the 10,15,22, and 23 holes of the playfield. I would think the
problem is above in the "Magic Squares" assy.
*********** BE CAREFUL....... there is 115VAC on the MOTOR TERMINALS.***********
See Pic below of schematic...........
ScreenHunter_207 Mar. 19 06.47 (resized).jpg