Help-Induction motor coil hum: how/where to place wood shims

[barnettrp21122]

Hello all:
I've determined that one of the coils on my Victrola type 3 induction motor is vibrating, causing the low-level hum when running. The advice I've read is to drive a small wood or cardboard shim between the coil and metal core, but where is this exactly?
I've attached a couple pics with markings, and hope someone can help. Thanks!
Bob B.

type 3 Induction motor coil 1.jpg (49.63 KiB) Viewed 1455 times

type 3 Induction motor coil 1a.jpg (23.21 KiB) Viewed 1455 times

[wjw]

Bob, I've never heard one of these motors that didn't hum a bit- especially when mounted in the cabinet (a very efficient hum amplifier). First make sure all plate lamination screws are tight, and mount the plate tight to the frame. Tiny wood wedges can be daintily tapped down between the coil and the "pole" it's wrapped around. This would be at C and D in your first photo.
I had a Credenza motor that had the little wood wedges neatly done a long time ago and painted over with some sort of black doping to hold them there.
An additional scheme is to further isolate the motor from the motorboard and the motorboard from the cabinet with modern neoprene washers. I have done this a couple of times and have learned to leave the mounting screws only slightly snug. It helps a bit with an obstinate hummer.
One other thing. If the rotor gets bent it can create a hum with a "wow" effect as the gap narrows and widens between the rotor and the coils. A rainy day fix for sure! -Bill

[barnettrp21122]

Thanks, Bill, for the advice. I plan to make up a workbench mount so I can see and hear the motor out of the cabinet and do some careful pressing and prodding to pinpoint the area as close as possible. I don't want to make things worse by being careless. I figure it'd be possible to ruin a coil if the wires are broken by a misplaced wedge.
I have two other machines with similar motors, and both have little or no hum, and my goal is to get this one to run as quietly as the others. Thanks again!
Bob

[Henry]

Neoprene wedges, the type piano tuners use, are available. I'm not sure it would be worth it to buy a whole tuning kit just for the wedges. Try google!