Capacitor maybe?

[mike wacker]

A buddy of mine (really) has a shop with several Walker Turner bench drill presses. One has a starting issue. When you give it power (120 volts) it shakes rattles and rolls, sometimes turning one way, some times the other. It has a 120 volt 1795 rpm frame size 56 (maybe) motor. Once you grab the chuck and give it a spin, the correct direction, it works fine. I'm guessing it has a bad starting capacitor. How do I check it. I have opened the capacitor cover and there is no obvous evidence of the cap being smoked.

[David G Baker]

Mike,
When I have problems with motors that are similar to the ones you described I replace the capacitor because I have found that most of the time that is the problem and capacitors are not really that expensive. I am not sure of how to test a capacitor to see if it is okay, another reason for my changing them when I start having motor starting problems.

[Rod Sheridan]

Mike, it can be the starting capacitor, the centrifugal switch or the starting winding (least likely).

If you have an ohmeter you can remove the capacitor from the motor, discharge it by shorting the terminals together, and then put your multimeter on ohms scale.

Connect the capacitor to the meter leads, the capacitor should show low resistance, rapidly changing to high resistance. Reverse the ohmeter leads and see that it does the same thing again.

If it passes the above test, it's not shorted, or completely open, which means it may be OK.

Obviously if it's leaking, swollen or burned, replace it.

You can check to see if your start switch and motor start winding are OK by measuring the resistance from the line to neutral pin on the drill press cord with your ohmeter. Record the value. (You have to put the switch in the ON position on the drill press).

Short the two motor wires that went to the capacitor and re-measure the motor resistance as above. If it has dropped substantially (maybe to half the previous value), your start winding and start switch are OK.

If the start winding and start switch pass the above resistance checks, it's the capacitor, replace it.

Regards, Rod.

[mike wacker]

Rod,

I can do that. Thanks for the detailed explaination. Fortunately I don't immeadiately draw blood when I pull out the VOM. ;o)