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MM180 - Non Auto-set Voltage control, ideas?

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  • MM180 - Non Auto-set Voltage control, ideas?

    Hello all,

    Been cruising the forum here for a bit trying to find if anyone else has had this same issue... was not able to find anything.

    I have a Millermatic 180 non Auto-Set. Serial: LH150607N. It is about 10 years old now and doesn't see a whole lot of use (a few pounds of wire over the years).

    Recently, I am unable to put wire speed over "40" without the wire pushing off the work piece. I narrowed it down and I believe it to be a voltage control issue.


    Things I have checked:

    DCEN vs DCEP (solid wire, 75/25 gas) Currently setup for DCEP at about 25cfh with .030" ER70S-6
    Line voltage in - 123VAC on each leg, 246VAC total with good earth ground - plugged in my Diversion 180 TIG and it welds perfect
    Ohm out all cables, main feed, ground clamp, torch lead and anything I could easily isolate within the welder
    Ohm out the rheostats for WFS and Voltage control, smooth from 0-50kohm
    Ohm out control rheostats to the main board
    Visually check the board, no signs of bulging/leaking caps, burned resistors, traces, loose spade connections etc. Very clean and the conforming coating is unbroken anywhere (welder is covered when not in use)

    I even pulled the torch lead, blew out the gas line and wire feeds super smooth by hand with little resistance through the whole liner.

    Last test before I decided I have voltage control issues is I turned the WFS and voltage knobs one at a time while attempting to lay a bead. WFS is pretty obvious when it changes, works fine. When I leave the WFS below 40 and crank the voltage around the weld puddle remains unchanged. Even if I disconnected the voltage rheostat in the welder, power it on and run it, welds exactly the same.

    Most of the problems I have found on the forum are wire feed issues so I am at a loss.

    I have ordered a replacement board since I am in a bit of a crunch for time, I hope when I install it the problem is remedied... I don't like throwing parts at things! (Replacement board order price jumped from $250 to over $380, order was refunded).

    If anyone has a schematic so I can pick apart the board and run back the voltage control, or anything else I should check? (Traced out the board, components checked out OK back to the program chip which I have no method to test).

    I am not an EE but I have no problem fixing/repairing circuit boards...

    Thanks in advance.


    I was able to find that the Millermatic 180 with Auto-Set board (Miller PN 238 912) fit my application on my non Auto-Set welder for less than the part number directly off the board in the welder.

    The Auto-Set board (238912) was $258.79 instead of the direct board replacement number (241863) for over $350.

    The welder now functions fully.

    SIDE NOTE: I am going to test and see if the Auto-Set function is present and functional and will update later.

    Thank you all for your input, I hope this may help someone else who might have this issue!
    Last edited by zbls2121; 08-12-2017, 10:49 AM. Reason: Issue Resolved, added notes.

  • #2
    Something I did to test my voltage control when I pulled my MM250 out of the weeds from some redneck's house....put my DMM on the welding power lugs inside and pulled the trigger. Adjusted it as the wire was feeding and watched the meter change in time with the knob as I turned it. Try that out.


    • #3
      I would also clean & doublecheck the ground/work cable and clamp connections....

      the oem tin clamps are famous for flaky connections as they get a couple years old..... creating problems

      lots of old threads on it

      many folks just discard and replace them with the TWECO style bronze clamps
      Click image for larger version

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      Last edited by H80N; 02-21-2017, 09:11 AM.

      The more you know, The better you know, How little you know

      “The bitterness of poor quality remains long after the sweetness of low price is forgotten”

      Buy the best tools you can afford.. Learn to use them to the best of your ability.. and take care of them...

      My Blue Stuff:
      Dynasty 350DX Tigrunner
      Dynasty 200DX
      Millermatic 350P w/25ft Alumapro & 30A
      Millermatic 200

      TONS of Non-Blue Equip, plus CNC Mill, Lathes & a Plasmacam w/ PowerMax-1000


      • #4
        Thank you for the input! I will have to try the DMM on the power lugs again, I did it during initial testing but have since forgot (frustration kicked in) what the readings were.

        I checked the ground cable with an ohm meter, it looks good. I even removed the clamp and bolted the cleaned end to my work piece. Checked and cleaned the lug in the machine too even though it looked ok. No change there.

        I have since pulled the main cap, my meter only goes to 1000uf (cap is 100k) but it ohms out ok. Checked the main xfmr coils and 24vac xfmer coils for shorts and winding resistance. Checked the rectifier board diodes (as best you can since they are pressed in) and the caps on it.

        Picture of the "clean" side below.

        I had ordered a board on Monday for $250... then got a call saying it was going to be $360.... Order cancelled.

        Thought I bought a Miller to have parts down the road but at a third of the cost of a few Miller (or almost a full cost of a Chinese one) I am disappointed to say the least.

        At this point I would rather have had a cheap one and just thrown it away and ended up with a new one and still be ahead in funds... but I digress.

        Click image for larger version

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        • #5
          Don't throw in the towel yet, let's see if we can get you up and running. Have you called Miller tech support? If you explain your problem, there may be an "ah hah" moment with one of them on the line.


          • #6
            Haha, I may have thrown a few things but the towel hasn't been one yet!

            I re-assembled the machine. Placed my DMM on VDC at the lugs, unlatched the wire feed drive and pulled the trigger on the gun.

            At any WFS or voltage setting the voltage spiked to around 30vdc, then quickly settled to 19.7vdc and then slowly climbed up to 31.5vdc after say 15-20 seconds of trigger time. No matter what I do with either WFS or volts the reading does exactly that each time.

            Is this the correct test method? Make sense/good or bad?

            I have not contacted Miller yet as their hours are too close to my work hours! My work is a large Miller customer so I have to follow up with our prototype/fabrication unit for a Miller contact... hopefully I can find time tomorrow to do that.

            Thanks again for the input!
            Last edited by zbls2121; 02-21-2017, 07:00 PM.


            • #7
              Is it possible to squirt CRC quick drying formula electrical contact cleaner into the rheostat to clean it? Maybe a shorted wire or a loose wire harness plug- in at the board?


              • #8
                Checked all that, rheostats work great all the way to the board.

                I did get a few mins to speak to the Miller tech support line... I provided some of my measurements from the day before. Looks like the rectifier diodes took a turn... New rectifier parts incoming... I will be sure to provide an update!


                • #9
                  Miller tech support line guys are awesome.


                  • #10
                    Well... new rectifier showed up... measured only slightly different than the old one...

                    No change, another $80 in the can.

                    EDIT: I should add so that anyone else searching for this problem, Miller tech support said if the rectifier board didn't fix this problem the next piece to replace is the $360 control board.

                    Anyone want to buy a for parts welder to help fund my next purchase?
                    Last edited by zbls2121; 02-27-2017, 07:53 PM.


                    • #11
                      I always pull the power disconnect on the wall when I'm done welding to protect my machines from lightning and power spikes.


                      • #12
                        This wasn't caused by lighting or some type of misuse. The welder sits covered, disconnected with the cylinder capped when not in use (Which is often).

                        I bought it brand new back in 2007. Put 3 rolls of 2# solid wire through it and am barely into my 8# roll and it took a crap.

                        By the looks of it, this board was not that great to begin with... as the replacement board is a few versions after the one in the machine.

                        I hope my Miller Diversion 180 doesn't screw me over... but then again I bought it used so at least I saved some money up front.

                        Is there a classifieds or refurb Miller (or other) section in the forum?

                        Thanks again for all the input.


                        • #13
                          Reviving this post as my MM180 non Auto Set (sn# LH150448N) just took a nosedive and the board is shot. The original board has been discontinued and cannot be obtained. I will probably order this board to replace it. Questions:

                          - Was this part 238912 plug and play?
                          - Is it still working for you?
                          - Did the Auto-Set work for you?
                          - Did you lose any functionality?

                          I'd appreciate any info you have. I only this use a couple times a year for projects and it's drag that it's now an anchor.

                          If anyone has any info on this please chime in. I realize the OP hasn't been on in quite a while.