motor just hums

deves2 · Post by **deves2** » Fri Jan 17, 2014 7:29 pm

I tried spinning the sanding disc and throwing the start switch but still nothing other than a hum
I will go back in the garage tomorrow to get info JPG requested. (busy tonite)
as far as taking it apart that doesnt bother me I just dont want to buy parts I dont need and sure dont want to screw up anything else.
tomorrow!!~

JPG · Post by **JPG** » Fri Jan 17, 2014 7:36 pm

We will likely want pix!

beeg · Post by **beeg** » Fri Jan 17, 2014 7:42 pm

deves2 wrote:The unit is from mid 70's and so far has been great ....no problems except for the mentioned switch.

For JPG, who missed it.

JPG · Post by **JPG** » Fri Jan 17, 2014 7:58 pm

beeg wrote:For JPG, who missed it.

Of course I missed that!:rolleyes:

He initially said it was an 'old Mk5'.

But alas I was not paying attention!:o

Fergit the ?:)

It is all 'internal'.

deves2 · Post by **deves2** » Sat Jan 18, 2014 4:17 pm

Saturday update:
I lowered the motor and blew out all the debris on the motor and everything else inside the case. Motor spins freely connected to all belts moving by hand. Removed the switch and direct wired the motor to an outlet and the motor worked every time it got plugged in to the wall socket. I noticed that on one of the lugs on the switch there was some corrosion and it looked like it had arced a little. (black on lug with corrosion) I cleaned the lug and re installed the switch. Now the smitty starts about 60% of the time but when it doesnt start I can rotate the spindle to get it to start.
I am still leaning toward the switch being bad. (i know it doesnt make sense to me either.....should either work or not work)
do you guys have any other suggestions>????

billmayo · Post by **billmayo** » Sat Jan 18, 2014 6:07 pm

You can use either side of the switch for the black & blue wires and jumper the white wires together without them going to the switch to checkout the switch. When the motor hums, it means that the start windings are not getting any electric to its windings to help start the motor. Where are you located? You should add your location to your profile. A Shopsmith Forum member may be nearby to help.

billmayo · Post by **billmayo** » Sat Jan 18, 2014 6:22 pm

billmayo wrote:You can use either side of the switch for the black & blue wires and jumper the white wires together without them going to the switch to checkout the switch. When the motor hums, it means that the start windings are not getting any electric to its windings to help start the motor. Where are you located? You should add your location to your profile. A Shopsmith Forum member may be nearby to help.

This is the picture from Shopsmith for the above wiring.
[ATTACH]23815[/ATTACH]

JPG · Post by **JPG** » Sat Jan 18, 2014 6:29 pm

My lean matches yours!

Unusual though!

May be poor contact by the terminals to the wires.

Just curious, what is the hp rating of the switch?

wa2crk · Post by **wa2crk** » Sat Jan 18, 2014 6:51 pm

JPG
I think that in the first post he said that replaced the switch with a SS switch but he did not say if it was a new one or a used one. I assumed new. However it would not be the first new part I found to be defective. I am beginning to suspect that the Centrifugal switch mechanism is being obstructed and the actuator is not moving freely and causing intermittent closing.
Bill V

JPG · Post by **JPG** » Sat Jan 18, 2014 7:03 pm

Good point! If the start switch has been intermittent, the arcing from turning (the hum) off will be destructive of the power switch contacts.

He has blown out the motor and it seemed the start switch was making reliably when it was direct wired, but since spinning gets it to start up now, that brings us back to the start switch.

I think it was not making at all before blow out, and is intermittently making now. Rotating the armature causes the start switch to make and it starts up.

Is this an Emerson motor? Pesky start switch contacts to 'clear'.