# X2 Minimill DC Drive Failure



## agr (Aug 23, 2011)

So there I was, excited at using my rotary table my X2/C6 (Grizzly 0516) lathe/mill for the first time when without warning the spindle just slowed to a stop. Checked the speed control & emergency stop - still OK & the green "power" light was still on? Did the logical thing and turned it off then on again (because that usually fixes most electrical things  ) - still nothing.

I had only been milling 6061 Al with a 3mm mill & fairly light cuts - but I had been going for 1/2 or so. Maybe the motor has overheated? - turned the power off for a length of time but still no signs of life when switched on??

It then occurred to me to check the fuse mounted in the front of the control box below the speed pot - blown! Of course it was a 3.15Amp fuse & the best I could managed in that size was a couple of 5amp ones - Oh well, worth a try. However in my excitement to get back to milling (combined with the el-cheapo fuse holder) on re-inserting the fuse there was that dreaded noise of breaking glass. Several minutes with the pointy nose pliers and some thin wire (& power off) I managed to extract the glass and insert a new fuse successfully.

Powered back up but still nothing - removed the new fuse and sure enough the wire was vapourised - Time to employ the help of Google!!!

After coming across this site http://www.raynerd.co.uk/?p=567 I recognised the symptoms I had - perhaps I had the same issue with a failing bridge rectifier - the electronic component responsible for converting the AC mains into a rectified (but 'rough') DC voltage.

Of course my lathe/mill is located up against the garage wall & the control board is mounted in the enclosure on the back of the machine - but with a couple of stubby screwdrivers & some stretching I managed to remove the board












Testing with a multimeter suggested that the rectifier could well be to blame as I could get continuity (0 ohm resistance) between one AC terminal and the + terminal with the meter leads in either polarity.








I unsoldered the rectifier to confirm the test out of the board & got the same results - so off to the electronics store the next day for a new rectifier (plus some fuses of the right rating)

The new rectifier was soldered into the board & reconnected to the mill & success :big: the mill was back to normal :big:


So there you have it - if you X2 mill stops unexpectedly & before rushing out to spend $160 for a replacement speed controller it might be worth trying to replace the rectifier first (total cost 10A rectifier + fuse $3.65).

Tony.


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## websterz (Aug 23, 2011)

Good on ya' Tony! I have replaced the rec's on both my x2 mill and my 7x12 lathe, and I keep spares on hand for both as well. Sure feels good being able to get going again on the cheap ,eh? :bow:


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## Tin Falcon (Aug 24, 2011)

Yep been there done it sweated in the t shirt. I had a power surge take out the bridge on my mini mill and a diode in the mini lathe ,IIRC the summer before last. 
Thanks for the right up may save someone a few bucks.
Tin


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## chucketn (Aug 24, 2011)

I had a similar problem on my X2, but it was the large coil in the center of the board. I unsoldered the broken end from the board, unwound the coil enough to reach the board and resoldered.
My problem was caused by the vibration of an interupted cut while making dovetails with a single insert dovetail cutter. I purchased a HHS dovetail cutter and binned the indexable one.

Chuck in E. TN


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## Sshire (Aug 24, 2011)

Most of us probably have surge suppressors on our computers, TVs etc but forget that some mills and lathes are also vulnerable to power surges. When my electrical panel was upgraded to 200A service, I had the electrician put a whole house surge suppressor on the panel. IIRC the suppressor was less than $100 at Big Orange Box. This way I don't have to think about which stuff needs this kind of protection. 
It's a simple job to add to the panel. 
Best
Stan


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## Troutsqueezer (Aug 24, 2011)

In my younger years I was in the electronics repair business for a major company where I fixed literally thousands of "brown goods" (this refers to consumer electronics whereas "white goods" refers to large appliances). These included TV's, VCR's, stereos, scanners, all of it. I would estimate that 90% of the time, anyone with the moxy to dismantle their equipment and closely study the inner workings of the apparatus can find the cause of the problem. Simple continuity checks, such as the one you did across the bridge, are all that's needed along with a sharp eye and some inclination as to what a proper solder joint should look like. 

I hadn't realized the X2 had this weak point. Filed away for future reference. 

-Trout


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## Noitoen (Aug 24, 2011)

I would install an heatsink on that rectifier if it doesn't already have one. Also a word about switchboard power surge protectors, these devices decay in time and should be replaced from time to time. Some brands have an indicator that shows when it's time to change.


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## agr (Aug 24, 2011)

Noitoen - I did consider strapping a heating to the rectified before I re-installed it but thought that since the rectified was rated at 10 amps, and the mill is protected by a 3 amp fuse overheating should not have been a factor? I assumed it was just the use of cheap components that lead to premature failure?

I also forgot to mention that on the web page linked above is a link to a pdt manual for the circuit which provides a schematic for those that need to delve further into the workings.

Tony


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## moanaman (Aug 25, 2011)

Had an electric problem with my 4 month old X2 a couple of days ago. When I turned in on and tried to set a speed, it moaned then ran very slowly, then stopped altogether , After switching off and turning on again a couple of times, always same result. Lost the plot completely. Normally I would have grabbed screwdriver, spanner and anything else including big hammer and rip into said electrical box,  but eventually calmed down and hit the emergency stop button, reset it and away we went, all better. 

Barry G


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## Troutsqueezer (Aug 25, 2011)

agr  said:
			
		

> Noitoen - I did consider strapping a heating to the rectified before I re-installed it but thought that since the rectified was rated at 10 amps, and the mill is protected by a 3 amp fuse overheating should not have been a factor? I assumed it was just the use of cheap components that lead to premature failure?
> 
> I also forgot to mention that on the web page linked above is a link to a pdt manual for the circuit which provides a schematic for those that need to delve further into the workings.
> 
> Tony



I would feel the diode bridge after the machine has been running awhile (carefully) and see how hot it runs. If it runs cool, instantaneous current could be what's killing it. A three amp fuse will pass much more than three amps for a short period of time before it blows. The bridge, on the other hand, will not survive a short term surge of current beyond its rating.


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