Broken Nova Comet II

[David Quillen]

Hi everyone, new to the forum and need some help. I bought a Nova Comet II a couple of months ago and have really enjoy learning to turn. Last weekend I smelled something funny when turning a bowl and then the lathe quit. Opened the motor control box up and found a burn up NTC thermistor. I looks like a flat capacitor. I think when the overload switch was installed it pushed the thermistor and the wire leads that are attached to the circuit board got close enough to each other to short.

I live in Florida, 2 hours from Teknatools headquarters, but that didn't help. Spent all last week frustrated with unanswered emails, unclear responses and I still don't know if they are going to get me up and running.

If anyone has a recent comet lathe and would look into the control box to tell me the specs on the thermistor, I might be able to put one in and be up and running. Got to be a 25 cent piece. The first picture is the burned up thermistor resting on the motor. The second photo is of the motor control unit. Unfortunately the flash refection is exactly were the thermistor was from.

Thanks!

David

313768313770

[John K Jordan]

Can you trace how it is wired in the circuit, specifically, is it an inrush current limiter? It appears it may be, since it is an NTC type. I believe those are sized based on the load. I'm no electronics expert but I have a good friend who is and might be able to tell from how it's wired. Do you think the short was between the two legs of the thermistor? If in series with the load it seem unlikely a short between the legs would blow the thermistor since the current would be through the legs and bypass the component. I hope the short didn't pass startup spikes to fry something else, but maybe not since the failure didn't happen at startup. Maybe it was defective - they are designed to have high resistance when cold and lower when warm, maybe it overheated. I would worry that some other failure fried the thermistor.


If you can get more info, I could ask my buddy Joe. He knows everything.

Curious, what is this overload switch and why was it installed? Was it installed by the factory, retrofit or something?


Maybe you could pull the board and drive over to headquarters and insist they look at it! Assuming of course that there are more than bean counters there.


JKJ

[Jim Underwood]

You called them on the phone yet?

[David Quillen]

To answer John's question about the overload button, I may have describe it incorrectly. It is one of those mini circuit breakers. Too much strain or such and the little button pops out and disconnects the power. It was original with the lathe.

To Jim's question, yes, called a few times. Finally found out today that they will ship me a new motor controller when they next get one in stock, week or two?

Thanks for responding to my questions.

David