No special tools, but the repair is likely to involve quite a bit of dis-assembly, including unsoldering and resoldering wire connections. Another poster opinioned that the handle may have slipped on the shaft. IMHO, those handles are really quite firmly attached to the shaft. As I recall, the shaft is knurled, and the handle appears to be cast right onto the shaft. I don’t think it can slip. On the other hand, it would be rather unusual for the wiper arm to slip on the shaft too. The original poster commented that this problem occured once before. Perhaps the wiper arm was not properly attached at the factory, and is a bit loose. The previous repairman might have used a chisel to stake the arm in place on the shaft, which loosened over time. If that’s the case, the arm could be staked again, but I’d look for another control assembly. They were fairly readily available a couple of years ago (new, old stock). Perhaps there are still some around.
That is exactly what I would do. I don’t see a downside if the rest of the transformer checks out OK.
I understand the photo that lionelsoni posted & that it is of the C-D side of the ZW. And yes, off of the windings to the left & onto that vertical metal plate is what the throttle wipers contact when in the max ON position. What I was referring to was the same (to me) type of vertical metal plate to the right of the windings. My C throttle does not go that far but remains to the rightmost side of the winding in the OFF position. In contrast, the D wiper (as well as A&B on the other side) come to rest on that vertical metal plate adjacent to the windings when OFF. I have the same black arc path on the windings as shown in the photo, although 2 of them on each side with the lower ones made by the A & D wipers, but again, the C wiper remains in contact with the extreme right of the windings when the C throttle is in the OFF position.
One correction to my previous post, the vertical “metal” strip to the rightt of the windings is in fact probably black plastic (it is non-magnetic at any rate). I just assumed by its appearance that it was metal like the one on the left, but my wiper movement description remains the same.