# Need Help From Any G0704 Owners



## wrmiller (Sep 6, 2014)

Have a question for any 704 owners here:

Have you guys had trouble with the motor/electronics on your machines? If so, what were the symptoms?

Today, I was looking forward to working on a little weekend project that required some mill and lathe work. Always a good thing.  

So I'm working on the mill, to the tune of about 3 hours, and about half way through I started noticing the display acting weird (all one number, gibberish, etc.) but it would clear and properly read the motor rpm after a few seconds. Motor wasn't hot, neither was the control box, and I wasn't pushing the machine hard at all, as I don't like to do that with these small mills.

Things started getting worse, right up to the point where the display just stopped working. Motor will spin, but I can't tell if it's turning at the right speed for a given position on the speed knob. Back of the control box was very slightly warm, but that's it. It is too much to expect these machines to run at say a 70% duty cycle over a three hour period? 

Disappointed doesn't even begin to describe the situation...

Bill


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## tmarks11 (Sep 6, 2014)

wrmiller19 said:


> I started noticing the display acting weird (all one number, gibberish, etc.) but it would clear and properly read the motor rpm after a few seconds....Things started getting worse, right up to the point where the display just stopped working.



disappointing for sure. 

If I was a betting man, I would say that you have loose wiring between the control module and the display based upon the symptom of the display switching to gibberish and back.  If you are handy with that sort of thing, I would take the front faceplate off the control panel (as you see in the upper picture below) and check that the ribbon cable (the upper white cable in the photo) between the display and the circuit board (shown in the lower photo) is firmly plugged in. 



It is possible that the spindle rpm sensor has failed or is unplugged, but I doubt it, since you said the display was showing gibberish.

Since the speed display is independent of the motor control, the speed you set on the control dial is no different than what it was before.  If you had a $20 hand-held photo-tach, you could check the speed to make sure it was what you wanted (which might be a short term solution until you can get repairs done). Without the tach, you are in the boat most people are in with mills without digital displays where they only have general knowledge of the speed.

http://www.ebay.com/itm/Handheld-Di...790?pt=LH_DefaultDomain_0&hash=item1c45cc0cb6


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## wrmiller (Sep 6, 2014)

Thanks for the help tmarks,

Being an embedded engineer used to working with microprocessors and such, that (your suggestion) was one of the first things I did.  

Reseated the cable, at both ends, reseated the socketed chip on the display board (socketed...in the 21st century?) and did a visual on the other cables.

Nothing.

After about an hour, to let things cool down, I went back out there and started the motor and stared at a blank display. Then a weird thing happened. After a few power cycles, I suddenly got all 5s on the screen. Then a little later, 8s. Then, finally I got a numerical reading that changed with the rpm. OK, sounds like bad/cold solder, or intermittent wire, or a socketed chip somewhere. Guess I'll have to take the thing complete apart and inspect under my magnifier.

Bill


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## kizmit99 (Sep 6, 2014)

Sorry to hear you're having issues...  I have the same mill and regularly use it in 2 to 4 hour stretches.  I have never experienced any issues (knock on wood).  I doubt I'm hitting 70% duty cycle during that time though.

From the symptoms you describe it definitely sounds like something gone bad in the display unit itself.  Given the shaking I've put mine through, I wouldn't be surprised if you find a cracked cold solder joint.  Even if everything looks ok, it wouldn't hurt (assuming you have some experience with soldering) to touch all the joints with a hot iron to reflow them.

Good luck!


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## mattthemuppet2 (Sep 7, 2014)

I vaguely remember someone on here toasting their control board in a similar mill, think it just overheated after a couple of hours use. I'd consider adding a small fan to the box the controls are in as a little bit of airflow makes a huge difference.


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## Rbeckett (Sep 7, 2014)

I would call Grizzly tech Monday and see if I could get it straightened out through them too.  They may have seen this issue and already have a fix.  

Bob


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## tmarks11 (Sep 7, 2014)

Well, that is (sort of) good news... at least the machine is useable in the short term.

When the G0704 was first released, there were some major issues with overheating the motor  or frying the SCRs on the control board.  The motor was redesigned slightly, and the electronics upgraded.  I haven't heard of any problems recently.  But matt could be spot on, you might extend the life of your investment by watching the temperatures in the instrumentation box (you have any thermocouples and a fluke lying around?), and maybe add a small 1.5-2" muffin fan if needed.

The overheating on the motor was primarily a problem (as I am sure you would expect) when operating it low speed for extended periods of time.  The internal cooling fan isn't much good when it is loafing along at 150 rpm.  One solution is to mount a decent 115V muffin fan on the back of it to keep up airflow.  Again, this problem might be OBE, some googling, maybe some reading on cnc zone (popular cnc conversion mill) could tell you if anyone has had a problem since the motor redesign.

http://www.cnczone.com/forums/benchtop-machines/123517-another-failed-g0704-motor-controller-2.html


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## wrmiller (Sep 7, 2014)

Thanks for all the help guys. Appreciate it!

I really was trying to take it easy on the machine so as to not hurt it. I need to 'hog out' some column braces out of 3"x5"x1" mild steel, and was using a USA made 3/8" solid carbide rougher taking .2" DOC and half to full width passes @ 1500 rpm. When the chips started coming out with a slight blue tinge, I backed down the rpm to ~1400.  

But the machine was running very smooth (no banging/major vibrations...really good cutter) and the motor was barely warm to the touch, which is why I was a little surprised when things went bad. I never did like the idea of having the electronics bolted directly to the head though. Who designs this stuff?!!

So during my major bout with depression yesterday, and while I was considering chucking the whole blink'n thing into the trash, I noticed yet another problem: 

Some here may or may not know that I took part in a early production run on a two-speed pulley kit for the PM/G0704 millls. After many months and a few part replacements, things were looking real good. Max spindle rpm is now 3800 rpm. But during yesterdays fiddling/power cycles while attempting to debug the display issue, I noticed a 'rattling' in the headstock at certain speeds. It appears that now the spindle can move slightly back and forth within the new bearing carrier's splines. I still have the first one I received that was for a PM25, which I don't seem to have, and noticed that the length of the internal splines that transfer power to the spindle are not even one third the length of those on the factory piece. Guess this wasn't engineered well either...  :angry:

Should have followed my gut and bought that G0695 in the first place. Now they are on back order. *sigh*

Thanks again guys, appreciate the help.

Bill


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## kd4gij (Sep 7, 2014)

Did you try cleanning the pickup on top of the spindle and adjusting it. I had to clean mine once as it was acting up.


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## Dr.Fiero (Sep 7, 2014)

Bad pickup wouldn't cause a loss of display. Most likely just read 0 rpm.


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## tmarks11 (Sep 9, 2014)

Bill, did you call Grizzly and inquire about replacement parts?

Are things still working for you?


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## wrmiller (Sep 9, 2014)

Motor works. I'm out a display for now, until I can troubleshoot some more. At least is still runs. May bring a scope home from work to see if I'm getting signals/pulse train to the display board. That would narrow it down some.

Can't call Griz as I didn't buy the machine from them. Unless I can pin it down to a specific part (display, control board, etc.) and pay for it.

I've got to figure out this spindle/spline issue before I go any further. Have an idea though. 

Bill


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## Smudgemo (Sep 10, 2014)

Focus on the board on the left side of the control box.  When my display died (during warranty), Grizzly threw at it two back boards, a display, a display cable, an RPM sensor, maybe something else I've forgotten, and finally the board on the left side (which fixed the display not working.)  Calling for help won't be much help.  Nice guys, but not terribly knowledgeable on my issue.  I kept wondering whether that board would be the  issue since that's where the display cable ran, but I figured I'd let them sort it out since that's what warranties are for.  

The other issue I had (which occurred at the same time) was the speed pot was dying about the same time causing the motor to not run to speed (I can't recall exactly what it was doing), but once the pot was replaced, it ran perfectly aside from no rpm display.  The guy said the pot is a common problem.  

-Ryan


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## wrmiller (Sep 10, 2014)

Thanks Ryan, appreciate the input. Figured the board on the left was the motor control, and the back board is the motor driver.

Pots are always suspects for failing early on these Chinese machines. Already planned to replace it with a wire-wound. )

Bill


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