motor just hums

deves2 · Post by **deves2** » Fri Jan 17, 2014 3:48 pm

I got ready to use the shopsmith (Old mk5) , moved the switch and the motor just hums. wont start.

I replaced the switch 18 months ago with a shopsmith switch could it be the new switch has gone bad already oir is it something else??
any ideas?

JPG · Post by **JPG** » Fri Jan 17, 2014 5:13 pm

deves2 wrote:I got ready to use the shopsmith (Old mk5) , moved the switch and the motor just hums. wont start.

I replaced the switch 18 months ago with a shopsmith switch could it be the new switch has gone bad already oir is it something else??
any ideas?

Start switch internal to the motor. Likely a speck of sawdust keeping it from making. Hit it a few licks with a soft faced hammer(the motor pan, or motor if accessible). Blowing it out may help.

Since it 'hums', the replaced switch is working.

Do not let it 'hum' too long nor too often. A half second is long enough o tell if it is starting up.

I could also be a bad/loose connection inside.

wa2crk · Post by **wa2crk** » Fri Jan 17, 2014 5:14 pm

Probably something else. If it hums the switch is making contact. It could be that the belt is stuck to one of the sheaves. Put the sanding disc on and try to turn the shaft by hand and then come back for further analysis.
Do not keep trying to start the motor with this condition cause it WILL burn out the motor.
Bill V

JPG · Post by **JPG** » Fri Jan 17, 2014 6:28 pm

wa2crk wrote:Probably something else. If it hums the switch is making contact. It could be that the belt is stuck to one of the sheaves. Put the sanding disc on and try to turn the shaft by hand and then come back for further analysis.
Do not keep trying to start the motor with this condition cause it WILL burn out the motor.
Bill V

Let us be clear when referring to 'switch'. The power switch is definately working if it runs or hums. If it hums, the internal start switch is likely not made(or loose/broke wiring, bad capacitor, open winding). The start switch is the most likely culprit. A speck of sawdust can prevent the contacts from making.

Yes a stuck belt can cause this or anything that prevents shafts turning.

So yes do try to rotate the shafts. If they turn, we can get back to diagnosing the motor. If they do not turn, then explore that direction.

deves2 · Post by **deves2** » Fri Jan 17, 2014 7:05 pm

UPDATE:
I can turn the sanding disc but the motor still will not start.
The unit is from mid 70's and so far has been great ....no problems except for the mentioned switch.

JPG · Post by **JPG** » Fri Jan 17, 2014 7:15 pm

As a simple 'test', set the speed to mid range. You should be able to spin it so it coasts slightly. with one hand to the power switch and the other on the disc, simultaneously turn it on and spin the disc. See if it then tries to run. If it does not, turn it off quickly. Most likely you cannot spin the disc fast enough for it to get started quickly(the disc will itself add inertia), but if it seems to be 'trying' to continue in the same direction, we can then concentrate on the internal start circuit.(yes disassembly will be in thy future).

JPG · Post by **JPG** » Fri Jan 17, 2014 7:18 pm

BTW, HOW old a Mark 5? Greenie? Goldie? 3/4hp? 1 1/8hp?

If an older model with a GE motor, all this start stuff is EXTERNAL!!!!.

Then disassembly will not likely be needed, but dropping the motor pan will.

wa2crk · Post by **wa2crk** » Fri Jan 17, 2014 7:18 pm

Then do what JPG said and tap the headstock softly with a rubber mallet to try to dislodge any debris stuck in the centrifugal switch which is inside the motor. If no luck then come back here for more info.
Bill V

wa2crk · Post by **wa2crk** » Fri Jan 17, 2014 7:20 pm

JPG
Me thinks that you and I are double typing.
Bill

JPG · Post by **JPG** » Fri Jan 17, 2014 7:23 pm

wa2crk wrote:JPG
Me thinks that you and I are double typing.
Bill

Simultaneously(near) more likely!:D

At least we are headed the same direction.