Drill Press Diagnostic?

[great white]

KInda points me back to the start capacitor being duff.....but I'm no electrician or electrical engineer. FWIW.

Ran across this on a google search, so take it for what it's worth:

"Why is the single phase motor changing the running direction without changing the wire?

There are a few possibilities.

1. Your motor may be lightly loaded (e.g. requiring very little starting torque to start the load) and the start centrifugal switch, the start capacitor or start winding may have failed. In that case the motor will sometimes randomly start in either direction (though more likely simply stand still and hum)."

And:

"George Stratton, President at G. E. Jones Electric Co., Inc. (1971–present)

I must assume you have a split capacitor type single phase motor because of the problem the you are alluding to. I would suspect a capacitor problem. Or perhaps a short circuit between the condenser winding the oil capacitor is in series with and the main winding in which case the motor should be drawing excessive current.

Now for the other types of single phase motors…

A split phase, both with and without an electrolytic start capacitor(s), requires a switch to energize the start winding. A bad switch or open capacitor would cause the motor to simply buzz…not rotate. However if you physically turn the shaft in ether direction it will run. Some larger split phase motors have oil capacitors placed across the starting switch contacts. I suppose it may be possible that there would be enough capacitance there to boost the start winding one way or the other without a load. Doubtful though.

The other type of single phase motor is the shaded pole motor. That motor can run in one direction only but can be reversed by removing the rotor and placing it back in the bore in the opposite direction. Therefore…No way this type motor would cause your problem."




Don't know if any of that helps, but more knowledge is always better than less knowledge.....

 

[woodchucker]

do you have a capacitor test function on your digital multimeter?
I would like you to test the new capacitor if you do.
remove it and attach it.
keep your hands away from the wires until you short the capacitor with a screwdriver or wire.
it is possible the new cap is bad.. it happens. I assume you got the same value right?

 

[A_Ninja_Racer]

I have a Multimeter and it has the Capacitance test functionality but I never seem to get consistent results. I did order the same spec capacitor.

 

[woodchucker]

I have a Multimeter and it has the Capacitance test functionality but I never seem to get consistent results. I did order the same spec capacitor.

Just see if you get a value close enough to the rated micro farads if close the cap is good.

 

[markba633csi]

The symptoms are telling us that the start winding is open- if you can't locate a bad solder joint (post #19) then it's time to find another motor
Some meters with cap function can only measure caps up to a certain value- start caps tend to be large-ish
Cap is likely ok
Always discharge big capacitors before handling/measuring

 

[RJSakowski]

1. If changing a capacitor out doesn't resolve the problem, it is highly unlikely the capacitor is at fault.

2. A light gauge or excessively long extension cord is not likely to be the reason the motor won't start. An 18 AWG extension cord will have a nominal resistance of .012 ohms/ft. At a current draw of 20 amps, the voltage drop would be less than a volt. Although starting current draw is high, the amount of torque needed to start the motor is low. Spinning the motor by hand will usually start a motor with a bad start circuit.

3. If spinning the motor by hand results in normal running, the run windings are most likely good and the start circuit is at fault. That can be due to a bad capacitor, a bad centrifugal switch, a bad start winding, or a bad interconnecting wire. Another possibility is that a P.O. wired the motor incorrectly. A resistance check on the start circuit should show close to zero ohms

4. The capacitor will be in series with the centrifugal switch and the start winding. If the motor is a 120/240 volt motor, the run windings are connected in parallel for 120 volt and in series for 240 volt operation. One leg of the start circuit will be taken from the center tap of the run windings when operating in 240 volt configuration. A connection diagram is usually posted somewhere on the motor. The capacitor may be at the end of the series circuit or between the centrifugal switch and the start winding If at the end of the string, one terminal of the capacitor will be connected to the line. Case .1 The other terminal will be connected through the centrifugal switch and the start winding to the other line terminal, the resistance should be very close to zero. If it reads open or a high value, measure the resistance from the centrifugal switch terminal connected to the capacitor. If it reads close to zero there, the fault is in the connecting wire. If it reads a high value, measure from the other switch connection. If it reads high or open the fault is in the connecting wiring or the start winding. Trace the connecting wiring back to the start winding and measure the resistance to the line terminal, A low resistance there points to a bad connection. This could be due to a break in the wire or to a bad terminal crimp.. You should be able to isolate the fault.

5. Although most faults are caused by a single failure. it does happen that double faults can occur. They are usually due to a shared root cause. They can be tricky to diagnose though.

I had a motor on a wire wheel that I had used for forty years with no problem. It was not a reversible motor sot the start circuit windins were hard wired. Changing the capacitor had no effect and the switch was good. I -opened the motor up and found a bad connection to the start winding. I repaired the bad connection and all is good.

 

[A_Ninja_Racer]

Just see if you get a value close enough to the rated micro farads if close the cap is good.

Here is another link to Youtube with my Multi-meter it just keeps jumping all over the place.

Capacitance Test

Here are some additional pictures. The ABC Brand is the new Cap.

 

[markba633csi]

The meter may be malfunctioning- You've tried a replacement cap and it didn't solve the problem
And the centrifugal switch seems ok so...
I'm pretty sure you have an open start winding in the motor- often a bad splice connection to a lead-in wire
which can usually be fixed- if you dig a little deeper you might hit pay-dirt

 

[woodchucker]

I agree, bad winding. The good news is that there are plenty of used motors on the market. Just look for the same frame , RPM and HP if you want the same.

 

[great white]

All meters are not created equal and that looks like a fairly.....*ahem*......"inexpensive" one.

I have several "cheap" ones around and they have their uses. I mostly use them as voltmeters and continuity testers. Anything else I reach for my BK precision or fluke meters. Checking a cap would definitely be more in the range of the BK or Fluke.....