Lathe revverse only

[j4872]

Hello,
Have read most of past threads relating to this problem but unable to solve my problem I am new to machining and very green to electrical. Will try to keep short
and on point.
Lathe Model Smithy BZ239. 110v similar to ENCO 110-2034
Acquired lathe recently. Forward and Reversed worked, but Forward not working since delivered and set up in garage
Forward hums but very little movement and will trip circuit breaker.
Replaced both capacitors on motor
Tightened all wire screws
Emergency button and other buttons work as expected
Switched power leads on micro switches and both appear to work fine.
Assume wiring at motor is correct as it worked before. However the wire leads out of motor are 5 blue
and 2 red. The red is larger gauge than blues. So no idea which is what when attempting to wire motor direct to a pig tail.
Energizing contactors, cause set buttons to recess.

QUESTION On testsing OHMs on wires from beginging of power source to contactors., I assume that the hot and common,( Black and White) wires should not have
an ohm reading when testing Black to White. However they do show a connection. This leads me to believe there is a short somewhere. Is this a bad assumption?
Any advice would be appreciated. Thank you

 

[cathead]

Motor windings have quite a low resistance so it is not surprising that that the winding would show continuity. Depending
on the ohm meter and the ohms scale set, it is possible to measure the resistance of the winding. Usually the ohm reading
would be an ohm or or so or even somewhat less than one ohm. If one has an ohm meter that has a X1 scale, you may
be able to differentiate between a dead short()ohms) and the resistance of the motor winding. Of course a winding may only
be partially shorted too so something to think about as well. Also if the motor has a starter winding, the reading may appear
to be abnormally low.

Welcome to HM!

 

[j4872]

Thanks for reponse, but these readings are with motor removed and wire terminals on V1,V2,Z1,Z2 are not touching, so should I still get a reading?

 

[benmychree]

If the motor runs in one direction but not the other, I'd look elsewhere for the problem.

 

[j4872]

Ok that makes sense. So does it appear there is a short in the system with the ohms reading across the hot and common ?
If I disconnect the bridging of hot wire and common to each respective terminal on contactor, then readings before that bridge have no ohms reading when cross checked. Does that make since? Hope that explanation is clear .

 

[cathead]

Thanks for reponse, but these readings are with motor removed and wire terminals on V1,V2,Z1,Z2 are not touching, so should I still get a reading?

If you are reading the motor winding only, then yes you should read a low resistance. On the other hand if a capacitor is
in series with the winding, it would show an open circuit.

Benmychree is probably right so the problem could be elsewhere.

 

[cathead]

Maybe with the power plug unplugged and the motor disconnected and the on-off set to forward, you could do
a test and see if the wiring is shorted on the way to the motor.

The process of elimination can be very helpful in determining where the problem lies.

 

[j4872]

OK will give that try and report back.
Thank you

 

[silence dogood]

I had a problem similar to yours. Except when I put the motor on reverse, it would blow a circuit breaker. After taking the motor apart, I found the neutral white wire from start winding was pinched between the motor cover and the motor housing. Reinsulating the wire and carefully putting motor back together solved the problem. What had happened was at first the motor worked fine in both directions. But as time went on the copper on the wire became exposed and shorted to ground. On forward it was not a problem. But on reverse the neutral became hot and shorted to ground. I know your problem is not quite the same, but it is something to look at. Another thing to look at, do you have chattering when you first turn on the motor especially on reverse? The contacts on the drum switch and maybe the on/off switch could be burnt. I had to replace mine (probably because of the short) and now everything works just fine. Hope this helps, good luck.

 

[matthewsx]

I have a similar lathe branded Samson. Problem is likely one of the contactors, mine did the same thing when I got it home but I already knew I wanted to change it over to three phase with a VFD.

Highly recommend this option if you can afford it.

John