# Failed (overheated?) X2 Mini Mill



## Jidis (Jun 15, 2018)

Hi all,

I screwed this thing up the other day and thought I fixed it, but evidently haven't. It's the Harbor Freight version (44991) with the regular cylindrical black motor.

I tried to hog too much steel a couple days ago, which caused what I thought was some sort of overheating protection. The machine was dead, but still getting power (good fuse, power light and exhaust fan active). I tried to let it cool a while, which didn't help, so I pulled the PCB from the rear box to check it (not quite as easy as it sounds). Nothing showed any obvious failure or signs of heat, and the solder joints looked OK. There was a forum post where someone had the main bridge rectifier fail, so I checked that and was getting no continuity (in circuit) on diode checks. I put in a beefier heatsinked one, but somehow the original read OK after I got it out (possibly poor probe contact when I checked it -my fault).

Anyway, all was well. It powered back up and I figured maybe that was it. I did a couple light tasks on it afterward, and went back to my steel dovetails tonight. After a couple decent cuts, it dies again. I wait a while and it still won't start. I give it a light Fonzarelli bump on the side of the control box and it starts, so I'm figuring maybe there's a bad connection I can look for later. I now think that brief rebirth was just coincidence, as it died again during the next couple cuts. No tapping in, or outside the two boxes changed anything, and the connections look solid. Unfortunately, I even pushed the new rectifier's heatsink into the nearby inductor and popped some sparks, so I'm hoping I didn't break anything new.

Any idea what this might be? The stalls and shutoff are clearly happening on strain, and seems likely to have started after that initial overload cut. It also has reached a point where nothing is even warm anymore, and I've popped the top off the motor and looked around, and don't see signs or smells of burning. During the brief times that it was running again, it seemed fine.

Sorry for all the text and any help is appreciated. 

Thanks!

PS- I'm guessing that small red LED on the power board is supposed to be lit?


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## markba633csi (Jun 15, 2018)

Hi, there is a guru who could fix your board for 50$ flat rate:
olduhfguy.com
however, you need to make sure the problem isn't the motor itself- does this machine have a lot of hours on it? Could the motor brushes be worn out?
You might want to try taking them out and inspect them if they are removable
Mark


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## Latinrascalrg1 (Jun 15, 2018)

If it's the same as mine then there should be1 or 2 adjustable pods on the board somewhere one that controls the torque Limits of the motor before the safety breaker kicks in or something like that..I dont remember exactly so verify but it should give you a place to start looking.


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## brino (Jun 15, 2018)

Jidis said:


> I give it a light Fonzarelli bump on the side of the control box and it starts



EEEHHHHHHHhhhhhhhhhhh! 

I had a look at the manual, nothing useful there.

Some similar troubles and good reviews of the repair guy mentioned above:
https://www.hobby-machinist.com/threads/harbor-freight-44991-help.67613/

-brino


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## Jidis (Jun 15, 2018)

Thanks guys!

Mark- Actually, it's fairly new, maybe a year and something with low hours. I also had the brushes out when I was looking at the motor and they look long and in good form, though they seem to put a substantial amount of carbon crud on the commutator. I cleaned it up a bit. 

Latinrascalrg1- I think I remember a row of maybe four little micro trimmers or components with trim controls, but I'd probably rather not mess with anything like that unless I know I can get it calibrated properly. I was also thinking that since pushing the machine too hard seems to have started everything, it's probably still in tune, but I might have damaged something (hopefully not).

I'll keep that repair guy in mind as a last resort, but I'm not opposed to desoldering or replacing parts myself if there's some usual suspect I can pin down. Still wondering about that red light too. 

Take Care


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## markba633csi (Jun 16, 2018)

Ok well, unless you are familiar with SCR phase-fired speed controls and have some test gear you probably can only get so far
I suspect a bad solder joint around the main current sensing resistor or in the power bridge section. 
If you can post some clear close up pictures of the board (both sides) I might be able to point out some possible trouble spots you could
try touching up with a soldering iron...
Mark
ps It kinda sounds like you might have blown a fuse the last time? There usually is one somewhere in the unit


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## Jidis (Jun 16, 2018)

Mark,

Thanks! I'm planning to get it out today, as it still isn't starting. I'm not so much interested in testing for the failed part, as just taking a shotgun approach and replacing a handful of the usual suspects to see if that covers it. I figure it can't cost but so much. It has a main glass fuse on the front of the control box, but I'm not sure there's anything other than that. When the main one pops, you get no power at all (fan doesn't run,etc.).

I was actually looking to get the board out anyhow, as I rushed it back in last time. Central Machinery (Harbor Freight) didn't do the best job of labeling on the wires. They've got numbered heat shrink bands near the ends which weren't ever actually heated, so a few fell off. As Brino noted, the manual isn't much help there, but the Grizzly 8689 pdf has a wiring diagram I was able to trace from. I want to relabel everything, but as much hassle as it is to get out, it would be nice to feel like it would be the last time.

Thanks Again!


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## Jidis (Jun 16, 2018)

Not the most detailed pictures in the world, but I guess they're something. Gotta cut some grass, but I'll try to look for cold joints and stuff when I get back in.

By the way- The bottom of these has been mirrored and aligned, so you should be able to tell who's who by bouncing from one picture to the other.


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## Latinrascalrg1 (Jun 16, 2018)

I understand your hesitation with changing any settings but I just want to say that I was having a similar issue.  Whenever I tried to take anything more then a scratch cut Into even aluminum with the machine in low gear a self resetting circuit would blow and I would need to wait and play with the switch to get it running a again.  Someone somewhere directed me to those pods and told me to give one or 2(cant remember)  a very slight clockwise turn and that if I was worried then to just mark the current setting.  Anyway when I gave the pod maybe 1/16 of a twist at most, My lathe does not "fault out" until a much higher torque resistance level is reached.  I'm no electronics genius and I did it with help and with you already willing to soldier on the board then adjusting a setting should be within your ability I would think!  Of course I would check for the weak link and look for a broken soldier joint but I maybe not.


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## Jidis (Jun 16, 2018)

Thanks Latinrascalrg1- It looks like they labeled the speed and torque pots, where the others are glued and unlabeled, so I'm a bit less afraid of it.

On a related note- It looks like they also glazed over the surface mount chips for some reason. I can't imagine it would be one of those deals where they don't want you to see what they are, but maybe something in the masking stage just blasted over everything.


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## brino (Jun 16, 2018)

Jidis said:


> It looks like they also glazed over the surface mount chips for some reason. I can't imagine it would be one of those deals where they don't want you to see what they are, but maybe something in the masking stage just blasted over everything.



hello @Jidis, it is commonly called "conformal coating" and is typically used like a weather-proofing layer, although it is NOT that good.
It does help in staving off moisture indused corrosion for a few years.
-brino


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## Jidis (Jun 16, 2018)

brino said:


> hello @Jidis, it is commonly called "conformal coating" and is typically used like a weather-proofing layer, although it is NOT that good.
> It does help in staving off moisture indused corrosion for a few years.
> -brino


Yeah, it just seems like those procedures usually spare certain areas. This thing looks like it randomly hit stuff. In addition to the IC labels, the whole top of one of the caps is coated, but not the others.

An additional question if anybody knows- I was checking the two MOSFETs as described in LMS' "drive troubleshooting" pdf. Everything checks OK, other than the last check which reads infinity across pins 2&3 regardless of how the leads are oriented. Is a normal multimeter supposed to care about that when it's in resistance mode?

Thanks!


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## markba633csi (Jun 16, 2018)

On that last check, do the two mosfets give the same result? If so then they are probably ok.
I'm not real familiar with the mosfet style controllers and would recommend sending it to olduhfguy.com for repair
I don't see anything obvious in the pictures
sorry
there is a fairly detailed troubleshooting section on his website, take a look


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## Jidis (Jun 17, 2018)

Mark,

That board is back in now, but I believe it was the same (no continuity) on both of the MOSFETs, where there was supposed to be some in the reverse direction between 2&3 if that's correct. One of the last things I did when it was back together, coincidentally, were a couple of the checks from that olduhfguy site. I think there was no DC happening on the speed pot lines. The motor ran about as well as I guess it's supposed to on an external 12V supply, so that seems OK. 

Unfortunately, the torque trimmer had no effect either, and it's one of those multi-turn things, which I rotated enough to have no idea where it once was. I think Jose Rodriguez had info on setting the lathe one, so I guess I can cross that bridge if the machine ever gets brought back to life.

This all sucks as I was finally quite happy with the adjustment of the mechanical parts and was enjoying the nice smooth belt drive mod I just finished.

Take Care


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## markba633csi (Jun 17, 2018)

No voltage at the speed pot means there's a low voltage supply problem, unfortunately without a schematic diagram it would be hard
to know what to do
I think spending 50$ plus shipping would be reasonable to get it fixed


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## Jidis (Jun 17, 2018)

Mark,

Actually there _was_ voltage at the P1,2,3 points. I'm having trouble getting good contact on this thing with a meter when it's installed, and I was in a bit of a hurry. I've got the MOSFETs, optocouplers, the original version of rectifier, and the two +/- 12V regulators on the way. I'll very carefully swap all that and check whatever else I can with a multimeter, then see what it does. Last resort, I'll see if the UHF guy will still mess with it. FWIW, this isn't a cheapness thing, but more for the experience and trying to get the machine back up as quickly as possible. I'm fortunate to have rework equipment here and understand the risks, so I'd feel kind of guilty if I didn't at least try.

Take Care

PS- That coating is a real mess. I saw other mentions of it when I looked up info on the power board. They slopped some sort of varnish all over a bunch of the parts, which makes things a bit difficult to probe (and probably remove for the surface mount stuff). I had to desolder a bunch on something one time that were actually_ glued_ down, but at least that wasn't covering all the leads.


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## markba633csi (Jun 17, 2018)

OK understood, just be careful not to damage the pc board traces- those chinese boards are notorious for coming apart at the slightest touch if you
don't have the proper rework tools and a sure hand
good luck


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## Jidis (Jun 21, 2018)

GRRRRR!!! Still waiting on parts from Mouser, I figured I'd double check a couple things, and just noticed one leg of that big coil is no longer going down into the board. It's possible it popped loose while I was desoldering or messing with it, but I remember another guy online mentioning the same issue and having to unroll a bit more to get back into contact, so it's possible that heat gets them sometimes. I'll still put nice new parts on there when they get here. If all goes well and it works, I guess I'll have spares.   * looking at the picture, it's got some scorching around the old joint


markba633csi said:


> just be careful not to damage the pc board traces- those chinese boards are notorious for coming apart at the slightest touch if you don't have the proper rework tools and a sure hand


Yeah, this was not the most friendly thing to work on for anybody that considers it. A bunch of the leads were such a snug fit that the desoldering iron couldn't free them effectively and I still ended up with a desoldering braid for a bunch of it. Then there's the wonderful lacquer or whatever. The board has that cheap, glossy look that reminds me of Asian motherboards and PCI cards I used to get from all those "PCChips" companies. It's a shame that they've made it non-cost effective to replace at >$100. It should be in the neighborhood of twenty-five or thirty tops.

<edit> The Fonz thing makes sense now too. I probably bumped it back into contact temporarily, then it worked itself open again after a few cuts.


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## markba633csi (Jun 21, 2018)

So was that the problem after all?  That's a main power filter choke


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## Smithdoor (Jun 21, 2018)

I replace the with better one try Amazon or eBay.
Even fix the broad you have it still a week

Dave


Jidis said:


> Hi all,
> 
> I screwed this thing up the other day and thought I fixed it, but evidently haven't. It's the Harbor Freight version (44991) with the regular cylindrical black motor.
> 
> ...


0


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## Smithdoor (Jun 21, 2018)

I replace the with better one try Amazon or eBay.
Even fix the broad you have it still a week

Dave


Jidis said:


> Hi all,
> 
> I screwed this thing up the other day and thought I fixed it, but evidently haven't. It's the Harbor Freight version (44991) with the regular cylindrical black motor.
> 
> ...


0


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## Jidis (Jun 21, 2018)

Hey Mark,

I probably won't know for (hopefully) a couple days when the parts show up. It's a prime suspect though as it was definitely burned through when I got it out. It's back on there now (minus a couple pieces of a millihenry  ). Wish I could have put something a little heavier on there knowing that the original is barely up for the task.


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## Jidis (Jun 21, 2018)

Dave,

Do you mean with a better _board_ or better version of that choke? I was thinking a little while ago how nice it would be if some generous nerd amongst us redesigned a nicer board and had the files up for DIY.


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## markba633csi (Jun 21, 2018)

I suspect that the loose choke wire was the culprit and that your board probably works now. I would STRONGLY suggest that you put the new parts aside as spares unless you really have a compelling reason to change them all out.  You can only make things more complicated for yourself. 
The operating phrase here is "do the minimum to get it back on the air"
Mark


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## Jidis (Jun 21, 2018)

Mark,

I _would_ repopulate the board, but with all the warnings I saw about how fragile a couple of them were, I'd feel like they were compromised parts. The opto's in particular were a pain to desolder and were said to be highly susceptible to overheating. I was careful to protect the board and surrounding parts during removal, but didn't care much about anything I figured was getting replaced.

Take Care


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## markba633csi (Jun 21, 2018)

Good luck, I hope it works


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## Smithdoor (Jun 21, 2018)

Jidis said:


> Dave,
> 
> Do you mean with a better _board_ or better version of that choke? I was thinking a little while ago how nice it would be if some generous nerd amongst us redesigned a nicer board and had the files up for DIY.


A new controller that is heave duty so does not go out

Dave

Sent from my SAMSUNG-SM-J320A using Tapatalk


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## Jidis (Jun 23, 2018)

It's back!!

Looks to be doing fine with the new stuff (knock on wood). I have no idea what that torque trimmer was at before, so I'll be going to look up info on how to set it later. I don't _think_ I messed with the speed one, but I've got a cheap handheld tachometer, so I may try to calibrate the machine to my belt drive pulleys while I'm in there.

Lesson to anybody that burns one of these up- Look up under that coil before you extract anything else (wish I had). For what it's worth, the coil measured as 14mH after unrolling one winding for repair. The pins are about 16mm spacing, and the wire is 0.8mm or something in diameter (maybe 20ga). Not sure what the original specs are, as the schematics I saw simply label it as "L" with no value.  This is the FC350BJ/110V board with the integrated digital circuit.

Take Care


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## hman (Jun 23, 2018)

Congratulations on getting it fixed!


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## markba633csi (Jun 23, 2018)

Cool, and I'm sure the inductor value isn't critical


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## Jidis (Jun 24, 2018)

Thanks guys! I'm not sure what the heck to do on that trimmer. Most people seemed to say they adjusted it until it cut off at some specific load. I swear I swung that thing in both directions for several turns with no effect at all. Not even sure what I'm expecting it to do. Not quite so bothered by it as I do have a belt drive, so that'll probably just slip if things get bad enough.

Take Care

<edit>- FWIW- I was plunging through a railroad spike with about a half inch drill bit while testing the pot. I was able to put enough pressure on it to make the belt slip, but nothing ever cut off.


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## Latinrascalrg1 (Jun 24, 2018)

If you are reffing to the torque adjustment pot I'm not sure what to say!  On mine when I turned it counterclockwise to the stop I was able to very easily get the overload protection circuit to kick in and cut the power with slight pressure from a single finger regardless of the speed. When slowly turning the pot clockwise the torque level increases before that fault circuit kicks in.  Before I adjusted mine, the lathe would fault out with a medium handshake type grip/pressure on the chuck. Taking even very shallow cuts into soft plastic was a problem but after adjustment I can now take nice cuts from aluminum as well as mild steel before it shuts down due to a torque fault!


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## Jidis (Jun 24, 2018)

Latinrascalrg1-  Thanks, that actually answers one of the questions I had if this mini mill board has a similar configuration. I had no idea _which_ direction might eventually trigger it.

On the plus side, it did overheat or something today during the drilling of a long 3/8" hole for a boring bar holder. That light came on and the machine stopped running, so apparently there _is_ something which will trip it. I'll mess with it again later and just take things slow and careful for the time being.

Take Care


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