New CX 709 motor problems

[Todd McBride]

I just bought a CX 709 from Busy Bee, used it lightly for a few hours and then the starter circuit seems to have failed. Push the start button, it doesn't turn, it hums, draws huge current then blows the breaker in about 5 seconds. If you throw the chuck over by hand as you hit the ON it starts just fine and I used it that way for a few hours to finish my first projects. But that probably isn't a good safety practice!

BusyBee provided a replacement capacitor on the assumption it was that start capacitor, I replaced it, and now the lathe starts immediately but makes heavy motor noise and blows the breaker in about 20 seconds. Took the belt off and the motor spins freely so no problems there despite the cold in my shop. I think the start circuit is staying on and that makes the noise and draws the heavy current.

Has anyone else had this problem with a new CX 709, or with any 110V induction motor made in China? What has BusyBee done to rectify these defects in the past? Do they hire an electrician, let the owner remove and replace the motor, or have the customer haul the whole unit back?

 

[PeterT]

It could be other things but I would check the centrifugal switch (assuming it has one). If it fails to engage & disengage properly it can impede how the capacitor is supposed to come on & off during start. The 'heavy motor noise' as you say is probably electrical cogging. Exactly what I had on my mill when the CS was not set right. (Different mill but common problem source apparently).

 

[Todd McBride]

That's my theory, the centrifugal switch is staying closed. Maybe that burned out the original capacitor and with it gone the lathe drew normal current in the main windings but had to be "kick started". I assume the new capacitor wouldn't last long if my 15A circuit didn't blow to save it. Didn't notice anything electrical when the first capacitor apparently failed, the lathe just buzzed but didn't start after we had shut it off one of many times on our first threading project. And it started immediately when I tried the kick start method.

I assume that whole motor has to be replaced since the switch would be inside. Now I just need Busy Bee to tell me whether they will send an electrician or should I disconnect it and return the motor myself.

 

[Dabbler]

PeterT had a similar problem with a 2HP motor on a mill. I think adjusting the contacts helped for a while. eventually the motor had to be replaced, I think.

Fortunately motor problems like this usually turn up early, like in the first 100 hours of use, then they work forever.

 

[PeterT]

In my case (different mill) the motor cooling fan was probably set a bit too close to the centrifugal switch to begin with. Over time it slowly worked its way down the motor shaft until it impeded the CS from opening, thus the start capacitor wasn't phasing in & out like its supposed to. The capacitor was replaced because it went bang but the motor was fine & continues to run. Your mileage may vary condition wise but that's why I think check into the CS. When you disassemble, make note of positions like with felt pen or mini scribe lines so you have some reference to trouble shoot.

 

[PeterT]

Your motor assembly may be different but just for illustration here is mine. The assembly sequence is: motor, contact plate, centrifugal switch, fan, end bell. In particular look at the condition of the points. If they are pitted or burned best to replace. Also check that wiring did not come loose, electrically that would equate to similar problems.

 

[Tom O]

Take a look at the brushes I had a few encounters with mine on my mill I think the springs are weakened when heated.

 

[DPittman]

What has BusyBee done to rectify these defects in the past? Do they hire an electrician, let the owner remove and replace the motor, or have the customer haul the whole unit back?

When I had headstock bearing problems with a lathe, BusyBee first told me that I needed to change the oil in the headstock...(my lathe does not have headstock gear oil)...they then told me they could order parts that I could install but couldn't tell me when those parts would come in, or give me any real useful instructions on how to make the repair. After some considerable "persuasion" from me, they agreed to take the lathe back and order me a new one. I then waited for months for the new lathe to come in and they could not tell me at the time how long that would take.

I have since decided that BusyBee tools are just like any other imported machinery that is readily available from numerous sources and therefore, unless the BusyBee price is cheaper than others, there is no reason to purchase from them (at least that's how I see it). And I find it is very rare that BusyBee has better prices.

 

[Dabbler]

Last christmas, they had a great deal on 3X79" sander/grinder. My metal/wood bandsaw CV101 was far less than the competition.

I'd never touch a BB lathe or mill again, knowing what I know now.

 

[Janger]

For a time I owned a cx701. At one point the rpm sensor on the shaft came loose and broke. I sent pictures to busy bee and they sent me a replacement part in a few days. I put it in the machine. Simple enough. I think they told me if it needed more extensive service I’d have to bring it to the store. It was heavy enough that there was no way I could just pick it up and throw it in the truck. Need a engine hoist. Anyway that is my experience. It seems to really vary from fine (me) to horrible (Don). I hope it gets resolved without too much drama.

 

[Janger]

Your motor assembly may be different but just for illustration here is mine. The assembly sequence is: motor, contact plate, centrifugal switch, fan, end bell. In particular look at the condition of the points. If they are pitted or burned best to replace. Also check that wiring did not come loose, electrically that would equate to similar problems.

Peter how does that switch work? Does the spinning motion open a circuit or close the circuit? It looks like the bent donut ring would be pushed by the spring wings in the switch but I don’t see what that does exactly.

 

[Brent H]

Hi John,

The centrifugal force from the motor spinning will cause the weights (second picture) to swing out and the unit in picture number 2 will snap into place releasing the bent donut ring opening the circuit and dropping the capacitor out of the circuit.

Things that typically go wrong: The bent donut ring assembly gets loose and fails to open or close , the centrifugal switch part (pic 2) gets loose on the shaft and does't open the circuit or keeps the circuit closed, the contacts weld together and prevent the capacitor from dropping out or the contacts are dirty and the capacitor is out of the circuit and motor won't start. Lots of other things as well.

I had a motor in a busy bee drum sander - Clogged up with sawdust and would't work. Cleaned up everything, motor ran great - built more dust collection to prevent further issues

 

[Todd McBride]

I noticed that the original capacitor was 60uF whereas the replacement one they gave me was a 260MFD. Unless I'm misreading the numbers that is a 60 micro-Farad capacitor changed to a 260 milli-Farad one, about a 4000 fold capacitance increase. Can that be possible? Could the starting circuit and windings possibly work with such an increase in the capacitor?

BB says tomorrow their warranty people will finally return my call and I expect to be pulling the whole motor and returning it on warranty. Hopefully that won't take forever.

 

[Brent H]

Peter how does that switch work? Does the spinning motion open a circuit or close the circuit? It looks like the bent donut ring would be pushed by the spring wings in the switch but I don’t see what that does exactly.

More info

Start capacitor AC induction motors
One way to improve on the single coil design is by using an auxiliary coil in series with a motor starting capacitor. The auxiliary coil, also called starting coil, is used to create an initial rotating magnetic field. In order to create a rotating magnetic field, the current flowing through the main winding must be out of phase in respect to the current flowing through the auxiliary winding. The role of the starting capacitor is to lag the current in the auxiliary winding, bringing these two currents out of phase. When the rotor reaches sufficient speed, the auxiliary coil is disconnected from the circuit by means of a centrifugal switch, and the motor remains powered by a single coil creating a pulsating magnetic field. In this sense, the auxiliary coil in this design can be regarded as a starting coil, since it is only used during motor startup.



Read more http://www.capacitorguide.com/motor-starting-capacitor/

 

[PeterT]

Its been a while since I pondered this. I thought I had it figured out at the time with the parts on the bench, now I'm actually scratching my head looking at my pics again. In the attached video (assuming its the same principle) it shows: Start mode: weights up = points closed. Run mode: weights extended = points open

Behind the scenes electrically Start mode has the start capacitor in the circuit. At some threshold rpm the CS & points take it out of the circuit.

Now the puzzle. When I look at my pics again it seems like when weights are up the (black plastic) plunger on the CS is long. When weights are extended the CS plunger is short. The CS has a collar on top with set screw so its fixed on the shaft. So I assume the plunger is acting on the top of washer spring, long would mean the points are open which is bass-akwards to video. Brent what am I missing here?

 

[Brent H]

Hey Peter,

So when the motor is sitting the weights are up and the black plunger is pushing the donut down - Points closed and the capacitor is in the system (Your picture #2). When the motor is running up to speed (about 70% full RPM) the centrifugal force will drive the weighted ends out and pull the black plunger away from the donut - (Your Picture #3) and the donut opens the contact.

I re-wrote my replay a couple times thinking it back over. With the spring force in there you should get that "click" as the motor builds up speed and the click when you stop the motor and it winds down. It is a good way to tell if the centrifugal part is working if that click is working properly.

One way you can tell if the contacts might be dirty and not engaging the capacitor is that your motor will not start - might hum - and if you spin the motor it will start turning on its own. Could also be a dead capacitor but not as likely. Those are pretty robust most of the time.

 

[PeterT]

I'm having dejavu all over again. I think I was getting the upper stop thingy mixed up with where the points contact. Does this sketch capture whats going on? Maybe what I am calling the upper stop is actually electrically tied to the run capacitor side of the circuit... so the washer point has to be in contact with either the upper or lower?

 

[Brent H]

Wow - nice drawing so fast - that looks correct to me. The electricity flows through the donut to the contact point (red) for the switch to allow the capacitor into the circuit. (motor not up to speed)

I am sure there are manufacturers that make this reversed (switch goes down to open the circuit) but your interpretive drawing works for me

 

[PeterT]

LOL, Excel 'cad drawing' to the rescue.

With this established, the only thing that still has me wondering now in hindsight was the influence of fan body which is clamped to the motor shaft slightly higher than the CS. I could have sworn it was impeding the counterweight action because I tried it with & without fan temporarily, with CS locked in same position on shaft. Moving the fan up (I presumed out of the way of CS) solved the issue, no more problems. Unfortunately I didn't take a picture of the underside at the time. Hopefully my brain cells will kick in & it will come back to me.

 

[Todd McBride]

On my CX 709 I found out that the 60uF capacitor was the run capacitor, the start one was mounted lower on the motor (and a bit out of sight) and it was a 300MFD capacitor, and surprisingly of considerably smaller dimensions.

Now I am waiting for BusyBee to send me a replacement for that 300 MFD start capacitor. I will also have to swap the original 60 uF run capacitor back in place of the 250MFD one they originally provided as repair. It was apparently OK.

Haven't figured out why a 250MFD capacitor installed in place of the 60uF run capacitor allowed the motor to start and run, though apparently at much high current draw. IF the problem was the other 300MFD start capacitor, and it had failed, why did the motor start with that erroneous replacement of just the run capacitor?