Bandsaw motor just hums, Capacitor?

[Mac McQuinn]

After doing a restoration on my old 1950's Sears (3) wheeled Bandsaw which has a 1/2HP Century motor, I plugged it in and hit the switch, it ran fine. After turning it on and off all a few times to check things out, it quit. Everything had been rewired along with new plug to duplicate original wiring and now when turned on, the motor just buzzes/hums and will pop the breaker button on my EXT. cord plug. I've checked for loose connections although found nothing questionable. Tried plugging direct into a wall plug, same thing...buzzes and hums. The motor had sat for 7 months and I'm not really sure of it's history although it did run the saw when purchased. I'm thinking the capacitor may have burned out, Any suggestions?


Mac

[Ken Fitzgerald]

Mac,

It's sure possible it's the capacitor. Does the motor have a pulley and drive a belt? If so, I would remove the belt and then plug it in and with the motor turned on, use something like the end of a stick and see if you can spin the pulley. Be very careful. Don't do this too many times. The motor turned on without turning can cause the motor to draw too much current and damage or ruin it.


Another possbility is that is the centrifugal switch in the end of the motor. If the switch gets sawdust in it, it may fail to close after the motor's shut down. This results in the capacitor not not being in the circuit and thus the motor won't start.

Also....often if the capacitor goes bad, the capacitor will split and you will see electrolyte oozing from it. This can be observed by removing the cover from the capacitor. Always unplug the machine when working on it.


Good luck.

[Mac McQuinn]

Ken,
Actually the first few times I turned it on and it ran fine was w/o a belt in place. I then installed a belt and it still ran fine. I was checking belt tracking and satisfied with that, I turned it on again and got the buzzing/humming. That is where I'm at at this point. I've only let it buzz for 1-2 seconds before shutting off. Motor did not get warm when it was running
Thanks for the input,
Mac


Mac,

It's sure possible it's the capacitor. Does the motor have a pulley and drive a belt? If so, I would remove the belt and then plug it in and with the motor turned on, use something like the end of a stick and see if you can spin the pulley. Be very careful. Don't do this too many times. The motor turned on without turning can cause the motor to draw too much current and damage or ruin it.


Another possbility is that is the centrifugal switch in the end of the motor. If the switch gets sawdust in it, it may fail to close after the motor's shut down. This results in the capacitor not not being in the circuit and thus the motor won't start.

Good luck.

[Lee Schierer]

It sounds like a capacitor to me. Turn the switch off, wind a piece of rope around the pulley and pull start it like an old lawn mower. While the motor is still spinning flip on the switch. If the motor runs your capacitor went bad. It can also be a stuck starter switch too.

[Mac McQuinn]

I pulled the motor back out and removed Capacitor. Took it to repair place and they stated it was still good and tested fine. I'm going to pull motor end plate to check things later tonight. I did take an air hose and blew out things from both ends and still get just a buzz/hum.

Mac


It sounds like a capacitor to me. Turn the switch off, wind a piece of rope around the pulley and pull start it like an old lawn mower. While the motor is still spinning flip on the switch. If the motor runs your capacitor went bad. It can also be a stuck starter switch too.

[Mac McQuinn]

Success. Upon pulling the end cover, I discovered a few things, The mechanism which activates the points was free and worked well although points had a small burnt spot and were pretty dirty. I cleaned these with a "Points File"(Still had one from my old 6 cylinder Chevy days) and then cleaned the residue off with contact cleaner. I then discovered what had happened.

There is a clear plastic retainer/seal in which shaft of motor slides through before fitting into bushing in the end housing. This had popped out of it's cavity in the housing and was distorted. I removed it and underneath was enough packed fine saw dust to fill the palm of your hand. It actually looked like cookie dough. It appears the sawdust had built up enough to force the retainer/seal out of the cavity causing it to press against the point assembly, forcing the points to close.

Once I cleaned out the cavity and blew the end housing off with air, I was able to get the retainer/seal straightened out and re-insert it back into the housing. I finished reassembling the motor, made the electrical connections and threw the switch, Voila, Ran like the proverbial clock.:D

Thanks Ken & Lee for your help!

Mac