Jet GHB-1340 noise

[glassford]

My lathe has developed a problem: the motor makes a horrible noise when I start it. I replaced the capacitor two months ago. It ran normally for a month, then became noisy again. It's the same "grinding" noise it made 20 months ago when I first installed a new capacitor. The capacitor becomes warm and emits a burning odor.

What could kill the capacitor so fast? Could the centrifugal switch be involved? I appreciate your responses.

I have attached a short clip which plays the noise.

 

[markba633csi]

Probably the internal centrifugal switch is malfunctioning and the contacts are not opening causing the capacitor to overheat. You should open up the motor and investigate. Sounds like you might have a bearing issue going on too. Listening to the motor by itself with the belt off would tell you more.
-Mark
ps I have a brother in Phoenix but he's pretty useless when it comes to electrical stuff-

 

[glassford]

Thankyou. I will look for dust, corrosion, and loss of contact.

 

[glassford]

I removed the dust cover and examined the switch. It looked good from the end, but the contact was hidden inside. I removed it easily. My goodness.

 

[markba633csi]

Wow, my goodness is right. Looks like half-dome lol
Not sure how I would repair it- I'm sure Jet would want to sell you a whole new motor
You might consider replacing the points completely with one of the new solid state motor start modules- Ulma Doctor did a post about them
-M

 

[glassford]

Jet Parts has a contact ring fixture gizmo for $17.00.

 

[glassford]

The contact ring is in the mail.
Further adventures in motor repair. I thought I might should look inside to remove any iron chips that might have fallen in when I drilled out a buggered screw for the fan cover and retapped the hole. There were some metal chips and some sawdust. Bearings run smoothly, so I won't try to change them now. The nuts on the tie rods were rusted. I will replace with plated allthread.

 

[glassford]

Bearings are sealed. I installed the new contact ring, the original centrifugal switch, the fan, and the fan cover.
Removing and installing fan cover is best done with the motor unmounted from the frame.
The motor now purrs

 

[Janderso]

Excellent.