No announcement yet.

Help with Millermatic 250

  • Filter
  • Time
  • Show
Clear All
new posts

  • Help with Millermatic 250

    Just picked up my first MIG, a Millermatic 250. Guy bought it a few years back, not working, with plans to fix it and he never did. I paid $150 for it including a Tweco torch, regulator, and even a nearly full spool of wire. I plugged it all in and tried running some wire, and it seems to work...sort of.


    1) There's a relay, CR1, and it has a couple wires that jumper between pins. Or at least they used to, now that those wires are burned through. I'm assuming that I'll need to replace those wires, but I know enough not to replace burnt wires without knowing what caused the problem in the first place. Any ideas? Should I just replace the wires and not worry about it, or is it a sign that something else may have gone wrong/is broken?

    2) The bottom feed roller, attached to the motor, is not aligned properly with the wire. I can change the alignment of the top roller with the adjustment screw, but I don't see any obvious ways to align the bottom one. It's off by maybe 1/16th of an inch. Is there any way to adjust it, perhaps by pulling the roller off the motor and shimming it, or should I not even bother?

    3) There's a ton of spatter/BBs. I'm guessing this very likely be caused by issue 1, above, but is there anything else to check? One thing I don't know how to do is verify the gas is flowing correctly. When I pull the trigger I hear and see a SLIGHT flow of gas, if I put my hand right at the end of the gun, and the flow meter reads 15 CFH when I do this, too. Since I have no other MIG machine to reference against, however, I have no idea what is "normal"

    Settings I used (came from a Miller guide I found): 1/8 material, ~200 IPM feed (switch on low, dial at 60%), 19V, 15 CFH gas, 0.035 wire

    Thanks is advance for any help!
    - Ian

    Click image for larger version

Name:	cr1.jpg
Views:	1
Size:	33.5 KB
ID:	531932

    Click image for larger version

Name:	bead1.jpg
Views:	1
Size:	52.6 KB
ID:	531933

    Click image for larger version

Name:	roller.jpg
Views:	1
Size:	32.7 KB
ID:	531934

  • #2
    Regarding the burnt wires to CR1, after a bit more research I discovered that there actually used to be a variable resistor there, VR1, which in the manual is listed as "VARISTOR, 75 joule 350VDC". Does anybody know what purpose this serves (or rather, served)? It seems like it's wired such that it bypasses the relay but I'm sure that's not what it does...perhaps some sort of surge protection?


    • #3
      I am no electrical genius by far but the vr1 provides resistance to cut down either voltage or amperage, depending on if it in series or parallel. That is highly likely to be what burnt them wires up. I would order it and put it back in where it was supposed to be replace wires and try it. As for the rollers shim them or whatever to make them line up. After you get that fixed try it again. Hope this helps