Failed (overheated?) X2 Mini Mill

Jidis

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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?
 
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
 
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.
 
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
 
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
 
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!
 
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.

MAIN_TOP.jpg


MAIN_BOT.jpg


XFORMER_TOP.jpg


XFORMER_BOT.jpg
 
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.
 
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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