Motor Run Capacitor...

[underdog]

Looking for a Motor Run Capacitor for a Jet mini 1014....

Yeah I burned it up somehow. I was batching out those little Oak handles the other night when I heard the motor slow down. I shut off the lathe immediately. It was still too late. I'd already let the smoke out of the capacitor and it don't work no more...

I began to review all the things I had done wrong.. and agonize over ruining a borrowed lathe, but that's for another post...

I've done a lot of research on this...

Jet sells this capacitor (JML-35-1) for $11.45. That's about twice what it's worth, but the really outrageous thing is that they're charging $19.95 to ship the stupid thing!

Supposedly it was a "run" capacitor. I've already asked the guys over in the Jet Tech department about it. They said it was a **edit(oops)** start capacitor, 25 MFD, 250 VAC.

So I looked around for a capacitor and thought I'd found one today. I trotted on down to the local motor store (Grainger didn't have it) and picked one up for about $5.00. It was a perfect fit under the cover... I mean "PERFECT". No room to spare.

I decided to do a little testing before I committed to it though... I checked the motor amperage with the capacitor on and off the motor. Without the capacitor, the motor ran at 5.06 amps (5 amps is it's rated amperage!), and needed a manual boost to get it going. Sure enough, with the capacitor, the motor started right up and ran at a low amperage (around 2-3 amps). So far so good. I was relieved that it appeared the motor was ok! BIG sigh of relief! (the motor is $135 from Jet- not to mention tax and shipping)

I decided to check my voltage in the building, and I got a good steady 120 VAC. I also decided to check the voltage to the "Start" capacitor after the motor started up to see if it was cutting off after the motor spooled up. NOPE! That was my first clue that this wasn't a start capacitor... The voltage across the capacitor leads was 238 VAC with the motor running. Or in other words 119 VAC to ground (although I didn't measure that). It was just after I felt the capacitor getting hot, and reached over to shut off the motor, that the thing blew... HISSSSS! the darn thing spewed black gook all over the place. Yup... I let the smoke out. again. Now it don't work no more either...

I took the motor apart expecting to find a centrifugal switch gone bad... Huh! This little motor is just about bullet proof! There's nothing in there but an armature, bearings, and stator windings! No brushes, no switches, NOTHING! I did find that the bearing in the pulley end was noisy, but that's easily fixed, (and understandable). I think it's a very common $6.00 bearing (6200 series double metal shield- NTN-62002 to be exact).

The interesting thing is that the capacitor leads are spliced directly into the motor leads and windings. In other words this has to be a "run" capacitor, because the voltage never shuts off. But it's confusing because it's a little black plastic cylinder, just like the start capacitors...

And that's where I'm stuck. I can't find anything like it anywhere but at Jet. And I'll be darned if I'm gonna pay 20 bucks for shipping something thats smaller and weighs less than my cell phone...

Just yesterday I shipped two 45 pound boxes for $11.50 each...

Got any advice, besides never borrow a friends lathe?

 

[arbud]

Have you tried to find the part at Radio Shack? I've had fairly good luck there.

 

[underdog]

Thanks for the idea.

I just checked on it but all they've got online are electronics capacitors. This is a relatively big capacitor (2 1/8 long x 1 1/8 diameter).

 

[Bill Boehme]

There some induction motors that use a single capacitor for both run and start and because of that they do not need a centrifugal switch. The capacitor is in series with a second winding and produces a phase shift in the second winding to simulate two phase power being applied to the motor where the two phases are slightly less than 90 degrees apart. In order to run most efficiently, the replacement capacitor when used for both run and start needs to be very close to the value of the original and also the voltage rating needs to be the same or greater. The fact that you measured 238 volts is not really relevant because you were actually measuring the voltage across the two windings which are not in phase with each other because of the capacitor in the circuit. If the replacement capacitor was the right value and voltage rating (and also suitable for continuous duty, UNLIKE a start capacitor which is only operated intermittently), then I would start looking at the motor as the culprit. If the insulation in the winding with the capacitor has broken down in places causing internal shorts, there may be too much current flowing through the capacitor, causing it to overheat. Since the winding resistances are so low, it may be difficult to measure any shorted windings and, besides, the arcing/short-circuiting may only happen when full voltage is applied.

Where to go from here? Try to measure the resistance of both sets of windings and then ask Jet tech support what readings to expect. If the resistance measurements are significantly off, it is likely that the motor is the problem. Otherwise, who knows? Well, a motor rewinding shop would know and they would charge a lot less to rewind the motor, if necessary, than Jet would charge for a new motor.

Did you verify that there is no centrifugal switch? It is almost always at the back end of the motor and sometimes can be sort of camoflagued if you don't really check closely. I re-read your edit and a start capacitor that is always in the circuit will not be long for this world.

Remember, the important thing is to not let the smoke out. Smoke is the magic ingredient that makes electrical things work. When the smoke gets out, things quit working.

Bill

 

[underdog]

Bill,

Thanks for the reply.

The new capacitor that I fried this evening was definitely a "run" (***EDIT*AAAGGHH- I keep doing this! It was a "START" Capacitor***EDIT***) capacitor and had no business being on the motor. The fact that it made the amperage lower seems to indicate that the motor is ok.

I see no evidence that the windings have been heated or are breaking down. This thing looks as shiny and new as the day it was built. It's totally enclosed. I know that is no guarantee, but the fact remains that I didn't have the correct capacitor. And that is where I'm stuck.

I guess I could take the motor down and have it tested, but that's $25... I'd rather find the correct capacitor and try that. Of course if the motors bad I'll spend that $25 frying capacitors...

Are you getting the idea that I'm a little tight with the money? 😀

As for the switch being "camoflagued". No way. I took that motor all the way down. Both end caps are off, the stator windings are completely visible on both ends. The three wire cord goes into the motor, and then is spliced directly into the windings and the capacitor leads. The armature is nothing but a shaft, the magnet, and two bearings. This thing is really slick. It's really bullet proof. There's nothing to break unless you really overheat it.

As for the Tech department giving me correct information, I'm afraid they've already handed out incorrect, or at least incomplete, information when they told me this was a "run" (***edit***And AGAIN! They told me it was a "START" Capacitor...***edit***) capacitor. This guy also said that the motor was ok running at 5.06 amp too. I don't think so...

Nevertheless, I'll see if I can dig the winding specs out of them..

 

[cjd]

If you were looking to order online at Jet, the twenty dollars for shipping is wrong. I ordered a couple of parts the other day that were less than a pound and the computer still said twenty bucks, so I called jet and asked, shipping turned out to be about two bucks. Hope this helps.

chris

 

[Bill Boehme]

Jim,
If there is no centrifugal switch, then the capacitor HAS to be a run/start capacitor since there is noting to switch it out of the circuit. A start capacitor is only in the circuit for about a half second before the centrifugal switch opens and cuts it out. I would open up the motor on my Jet, but I am not feeling that industrious right now. I have been all over the motor on my Delta 1440 and recently rewired it so that it could be reversed. It was very easy to do on that motor, but that is not always the case.
Bill

 

[underdog]

Chris,

Thanks for the tip. I was going to call Jet today and ask about this. I'll get off my can and do it for sure now.... I'd just as soon get the right part and quit hunting around at this point.

Bill,

I double checked for a centrifugal switch. Unless it's tucked into those splices which are covered by that braided insulation, there ain't one. So I'd guess that you are correct that it is a start/run capacitor. Where would I find one of those? 😕

You can rewire the motor to reverse it? I'd like to see how that's done. I bet this could be done on the Jet also.
Of course... what's the advantage of having a reversible lathe? 😕 😱

 

[Mark Mandell]

what's the advantage of having a reversible lathe? 😕 😱

The advantage comes for sanding and finishing. If you sand with the lathe running, it tends to make some of the fibers lay flat. When reversed, those fibers are "brushed up" and cut by the abrasives. You do have to be careful since putting much resistence on the piece or running with much speed will quickly unscrew your chuck or faceplate that is not specially fixed. 🙁

The other use is for turning on the outboard end of the spindle where the rotation is clockwise and would otherwise dismount the fixing and workpiece 😱 if the lathe were not running "in reverse" to get a standard counterclockwise rotation.

M

 

[underdog]

Thanks for the information. I've always enjoyed forums for this kind of thing. Always new ideas and ways of doing things.

I've ordered the capacitor now that I realize the shipping is less if I order by phone... $5.21 plus the cost of the capacitor. I wish I'd known that before I bought the other one...

And it's as I suspected. Jet's tech department didn't know any more than I did about the windings values, or even the fact that this was a run capacitor, and he didn't know whether there was a centrifugal switch or not (he just knew they didn't sell one).

So now to see if the windings are bad. I hope they aren't. I don't think they are....

I'll be calling my local motor repair shop to see if they can tell me how to measure the windings.

 

[Steve Worcester]

If you have the actual capactity and vendor part# of the capacitor, you may be able to get it from http://www.digikey.com/.

 

[Bill Boehme]

Hi Steve,

I am glad to see that you are up and around.

The kind of capacitors that you find at Digikey or any other electronic parts house are not suitable for motor duty use. The large value electronic type capacitors are polarized electrolytics and can't be used in AC circuits, especially where large currents are involved. I checked the motor on my Jet mini and there is NOT a centrifugal switch which means that the capacitor is a start/run capacitor and is in the circuit continuously. The fact that two capacitors failed in very short order would be overwhelming reason in my judement not to kill another capacitor just to prove that the motor is bad.

Bill

 

[underdog]

The fact that the second capacitor was a "start" capacitor is good reason to believe that continuous voltage made it fail.... 😀

At least that's what I'm hoping. I really don't think the stator windings are bad on this thing. It's a gamble, but it's a risk I'll take. (Besides that, it's too late, the thing has already been shipped.)

Seriously, how long would you guess a start capacitor would last under continuous voltage? 😕

I'm thinking that over agressive cutting and a pile of sawdust covering the fan on the motor made the capacitor fail... Of course that might have overheated the windings... 🙁

 

[Bill Boehme]

Now, I'm getting confused ......

.........The new capacitor that I fried this evening was definitely a "run" capacitor and had no business being on the motor. The fact that it made the amperage lower seems to indicate that the motor is ok.
............ As for the Tech department giving me correct information, I'm afraid they've already handed out incorrect, or at least incomplete, information when they told me this was a "run" capacitor. This guy also said that the motor was ok running at 5.06 amp too. I don't think so.....

and then in a subsequent posting:

..........The fact that the second capacitor was a "start" capacitor is good reason to believe that continuous voltage made it fail.... 😀

If the second capacitor that you used was a START capacitor, then I am not surprised that it smoked. My last reply was based on the post that you made earlier that the second capacitor was a RUN capacitor. If Jet sends you a capacitor, hopefully, it will be of the right type, even if they don't seem to know what that type is. Unfortunately, that is about par for "tech support" these days. Maybe you could have them tossed in the jug for non-support.

Bill

 

[underdog]

Bill,

No wonder things seemed a little out of whack....

For some reason I keep saying "run" when I mean "start". I did that in my first post also.. 😱

Thank you for pointing out my misdirection and sorry for the confusion. I've edited my post to correct that....

And yes, since the capacitor wasn't meant for continuous duty, it certainly doesn't surprise me that it's life was very short... 🙄

I'll keep you posted on the results of the new capacitor. I've gotten the new bearings and would love to put them in, but the wife said I couldn't do anything else until I get the kitchen painted for her birthday present... Not even pick up the new lathe that came in yesterday... Augghhh!.... that was agony.

Oh well. She's worth it. :cool2:

 

[Bill Boehme]

....For some reason I keep saying "run" when I mean "start". ....

The cause of this problem comes from using a computer with a Windows operating system. It is a medically recognized syndrome. Witness the following Microsoft tech support exchange:
You say that you want to turn the computer off and can't figure out how to do it? The answer is that you select START.

No, no, I said that I want to stop, not START!

That's what I said, you select START if you want to stop.

. . . . .

Somebody at Microsoft is an Abbott and Costello fan.🙂

Bill

 

[underdog]

Bill,

That's Hilarious! 😛

That's exactly what I was thinking. "Who's on First?"

Actually I've been getting more and more psychologically dyslexic these days...

I first noticed it in another life when I played the part of an auto mechanic....

Jump starting a car:

"Red on Positive, Black on Negative.... Red on Postive, Black on Neg.... Dang! where'd all those sparks come from... OH SH..." 😱

Abruptly realize that I've done just the opposite...

I think it's old age creeping up on me...

 

[underdog]

Got the new capacitor the other day. I put it and the new bearings in and now the motor runs quiet and at low amperage. (I think it was a little over 3 Amps.) So now the old Jet runs like a new one....

Well not exactly. The headstock bearings are making quite a whining noise, but I figure they've seen a lot of miles. If the owner wants to replace them as well, I'd be happy to do it for him. I don't think it's too big a deal. I''m wondering what kind of bearings are in it. Those for the motor were pretty inexpensive.

I also picked up my new Jet mini yesterday, but have only had time to get it out of the box. I did check its run amps just for grins, and of course it has a lower amperage than the old one (about 2.5). I wonder if the bearings for the old one need a chance to break in?

I also picked up that 5 piece Pinnacle chisel set for $99.00. Couldn't afford to get the chuck too... I almost bought the chuck instead.