Jet bench grinder and PA Multitool problem

[drewvdw]

I've got a JBG8 with a PA Multitool belt sander mounted to it and its acting like the startup capacitor is shot. I called Jet and they sent me a new capacitor and after installing, there is no change. Still have to start it spinning by hand before it will run and it takes a long time to get up to speed. I tried removing the belt and then it would start up without issue, just taking a little longer than I think it should. Has anyone else ran into this problem with these products? I've thought about buying a larger capacitor, the Jet unit is a 200 MFD capacitor and I think I could physically fit one up to around 550 MFD in the original location, but I want to make sure that that is the problem...not that spending $10 on a capacitor would be terrible, but I just want to be able to use the damned thing.

 

[Dingleburry]

I've got a JBG8 with a PA Multitool belt sander mounted to it and its acting like the startup capacitor is shot. I called Jet and they sent me a new capacitor and after installing, there is no change. Still have to start it spinning by hand before it will run and it takes a long time to get up to speed. I tried removing the belt and then it would start up without issue, just taking a little longer than I think it should. Has anyone else ran into this problem with these products? I've thought about buying a larger capacitor, the Jet unit is a 200 MFD capacitor and I think I could physically fit one up to around 550 MFD in the original location, but I want to make sure that that is the problem...not that spending $10 on a capacitor would be terrible, but I just want to be able to use the damned thing.

Does it move at all before you hand start it? Or just hum and not move?
Check the motor spins freely?
Check that you didnt get a faulty cap?
Check that the belt spins freely?
Check the centrifugal switch isnt stuck open?
Check ohms (or for an open circuit) across cap leads w/o cap installed? Cycle the cintrifugal switch by hand with dmm on cap leads see if anything changes.
Perhaps its not anything to do with your sander and something before your sander. Supply power etc.


I think.. putting a bigger cap will increase starting torque by like 50% but double the amps. Apparently excessive oversizing can reduce starting torque.

Thats all i got for now.
https://gearmotorblog.wordpress.com/2010/01/26/hotrodding-capacitor-motors/

 

[drewvdw]

Does it move at all before you hand start it? Or just hum and not move?
Check the motor spins freely?
Check that you didnt get a faulty cap?
Check that the belt spins freely?
Check the centrifugal switch isnt stuck open?
Check ohms (or for an open circuit) across cap leads w/o cap installed? Cycle the cintrifugal switch by hand with dmm on cap leads see if anything changes.
Perhaps its not anything to do with your sander and something before your sander. Supply power etc.


I think.. putting a bigger cap will increase starting torque by like 50% but double the amps. Apparently excessive oversizing can reduce starting torque.

Thats all i got for now.
https://gearmotorblog.wordpress.com/2010/01/26/hotrodding-capacitor-motors/

It just hums and doesn't move
Motor and belt spin freely other than a few wires on my wire wheel sticking out
I'll have to go back in to work to do some more testing on it.

 

[6PTsocket]

Dingleburry mentioned the most likely cause. There is a winding inside the motor called the start winding it is connected to a switch called the cenrifugal switch. The other side of the switch is connected to the capacitor. The three components are in series across the AC line. When you turn the motor on the start winding and the capacitor help the motor to start. As soon as the motor starts, spinning weights that are part of the switch open the contacts, disconnecting tbe capacitor and the start winding. When you turn it off, as tbe motor slows down you should hear a click as the switch contacts close to be ready for the next start. It is simple circuit and the possible problems are esy to understand. The switch is stuck open mechanically. The contacts are dirty or burned up. There is a disconnected wire from the winding to the switch The winding is open. Put a meter across the switch to see if it is closed. Take a reading from the switch to the wires going to the AC line. You should read some resistance to one of those wires if the start winding is good. Make sure there is continuity between the capacitor and the other wire going to the AC line. You are not starting under load, There is no need for a bigger capacitor than the,one supplied. If it does not start by itself, this three component circuit is open some place. It is most likely the switch.. Either the weights are stuck or a spring fell of or broke or the contacts are dirty or burned. The whole switch is replacable as a unit. I looked at the drawing. I think it was part # 65.

Sent from my SM-G900V using Tapatalk

 

[Dingleburry]

You are not starting under load, There is no need for a bigger capacitor than the,one supplied

Oh yeah forgot to mention that. The cap isnt really for torque here. It is to give the motor direction. You can hand spin it backwards and it will run fine.

So your problem is part of the cap circuit. You just gotta pinpoint it!

Good luck! Let us know how it goes.