overheating AC turntable motor?

[TubeDriver]

After 15 years of use, I noticed that my WT turntable motor is running very hot. It is quiet and holds speed but the top plate gets hot. It uses an AC synchronous motor and has a trim pot that allows adjustment to reduce vibration. Part of the power cord near the motor has some shrink wrap that covers part of the trim pot and maybe a few other components (capacitors?).

Any suggestion for what I can do to trouble shoot this thing? Thanks.

[Roscoe Primrose]

Two things come to mind:

Lubrication. Take the belt off and see if the motor still spins freely. You ought to be able to give it a spin and have it keep spinning for several seconds.

It may have a capacitor to provide the phase shift necessary to provide pseudo-synchronous operation. If so, and if that cap is going bad, that could be causing some problems.

Roscoe

[TubeDriver]

Thanks. When I try to spin the motor pulley by hand, it feels "cogged" i.e. it does not spin freely, rather it turns and then stops as if on a detente.

When powered up it works fine (quiet, correct speed). I did accidentally leave the turntable on for 24 hours straight a while back and that is when I noticed the hot temps on the motor top plate.

I did some online research and I believe the motor is a Hurst SP-3116 600rpm, 115V, 60Hz, 10w unit. I sent Hurst an email to see if they still make this model.

Two things come to mind:

Lubrication. Take the belt off and see if the motor still spins freely. You ought to be able to give it a spin and have it keep spinning for several seconds.

It may have a capacitor to provide the phase shift necessary to provide pseudo-synchronous operation. If so, and if that cap is going bad, that could be causing some problems.

Roscoe

[Guy]

Check that lubrication and let us know if anything improves (or not)

[TubeDriver]

It looks like a sealed unit, not sure where to lubricate?

Check that lubrication and let us know if anything improves (or not)

[Guy]

Hmm, you can try just a little oil (maybe 3-in-1?) on the exposed shaft and see if it will work into the bearing area with gravity and turning the shaft. The other bearing is a problem if we can't get to it.

Is the motor a permanent-magnet type? If so, that would explain some of the stepping or pulsing when you turn it - the rotor poles move from one stator head to another. I know it's an AC motor, so PM doesn't make a lot of sense.

Any response from the manufacturer about another motor?

[TubeDriver]

Hmm, you can try just a little oil (maybe 3-in-1?) on the exposed shaft and see if it will work into the bearing area with gravity and turning the shaft. The other bearing is a problem if we can't get to it.

Is the motor a permanent-magnet type? If so, that would explain some of the stepping or pulsing when you turn it - the rotor poles move from one stator head to another. I know it's an AC motor, so PM doesn't make a lot of sense.

Any response from the manufacturer about another motor?

Thanks Guy. I'll give that a shot. No response yet from Hurst. They have a motor which looks basically the same PN 3203-001 which is a 600rpm motor which the same basic specs. If I dont hear back from them, I might just order this and see if I can get it ti work. Motor is $75 which is peanuts compared to replacing the turntable. One other option is an OriginLive DC motor conversation kit which costs anywhere from $300 to $700 depending on options but will work and maintain the original appearence.

[TubeDriver]

I heard back from Hurst. The motor used fir my WT is a discontinued product. I was correct in that the 3203-001 is ALMOST a direct replacement with one large caveat. The shaft diameters are different. I sent a reply asking for the measurements for both shafts.

The WT motor has a press fit pulley that also use a set screw. The new motor (3293-091) looks to have a slightly larger diameter shaft. Any machinists here? What are the chances of successfully drilling out the pulley (aluminum)?