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  • Miller 135 problems

    I have tried the search and have read all the similar posts I can find, but still cannot seem to nail down my exact problem.

    I have a miller 135 Serial Number LC160100 and PCB assembly number 207463 LC-18.

    I bought this welder used and abused. When I got it, the wire feed speed was stuck at full throttle. I found a bad potentiometer and replaced that. After the replacement, the wire speed was adjustable. The problem is that it is adjustable from fast to very fast. At the lowest power and lowest wirespeed (with wire feeding) it is around 290 IPM. I haven't measured the quickest, but it is a lot quicker than 290.

    I took the board off and found that someone with very poor solder skills had at one time tried to resolder Q1 and Q2. From the lack of protective coating on Q1, I am assuming that transistor was replaced. I resoldered those connections... The voltage going to the wire drive motor is 11.8v at the lowest wirespeed and ~23 at the highest with the motor connected.

    Anyways, does anyone have any troubleshooting suggestions?

    Thanks for everyone's time.

  • #2
    I don't have a layout for the board in question, but motor control boards usually have a 'calibration' pot within the circuitry for calibrating the motor speed/WFS. Look your board over and if you find one, note its adjustment orientation and make a change to see if it affects the motor speed. If it does - dial it in. If not - return it to its original position.

    Here's an example. This one is ~1/4" square.
    Click image for larger version

Name:	Motor Speed Calibration Pot.JPG
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Size:	27.0 KB
ID:	508456
    MM200 w/spot controller and Spoolmatic 1
    Syncrowave 180 SD
    Bobcat 225G Plus LPG/NG w/14-pin*
    *Homemade Suitcase Wire Feeder
    *HF-251D-1
    *WC-1S & Spoolmatic 1
    PakMaster 100XL
    Marquette "Star Jet" 21-110
    http://www.millerwelds.com/images/sm...rolleyes.png?2

    Comment


    • #3
      Drive motor calibration

      Thanks. That is a good suggestion. I took a look on the board for a trimpot. I did find a small rectangular 10k trimpot, but unfortunately it had not affect on wire speed. I may not be seeing something, but I didn't find any other trimmers...

      Thanks
      Jeff

      Comment


      • #4
        Is it common that a bunch of resistors go bad on the control board? I pulled the board and was testing out some of the components. I don't have the board schematics, but I was going off of the resistor color codes.

        Some of the odd readings:
        R38 was 5.26K Ohm
        R41 was 5.26K Ohm
        R50 was 1.59K Ohm

        Comment


        • #5
          My guess is a bad darlington pair transistor. I repaired a MM 175 that had the wire speed on fast and even faster.
          The wire speed pot measured correctly so I knew it was not a problem with the pot.


          This thread might help.
          http://www.hobartwelders.com/weldtal...arlington+pair
          Last edited by crawler; 07-18-2010, 07:32 PM.
          Millermatic Passport Plus
          Millermatic 200

          Millermatic 350P with Python
          XMT 304 /w S-64 feeder and 12VS
          Dynasty 300 DX
          Thermal Arc 400 MST
          Victor O/A
          Premier Power Welder for my trail junk.

          Comment


          • #6
            Great info Charles. Thanks.
            MM200 w/spot controller and Spoolmatic 1
            Syncrowave 180 SD
            Bobcat 225G Plus LPG/NG w/14-pin*
            *Homemade Suitcase Wire Feeder
            *HF-251D-1
            *WC-1S & Spoolmatic 1
            PakMaster 100XL
            Marquette "Star Jet" 21-110
            http://www.millerwelds.com/images/sm...rolleyes.png?2

            Comment


            • #7
              Originally posted by duaneb55 View Post
              Great info Charles. Thanks.
              No problem Duane. Just trying to help.
              Millermatic Passport Plus
              Millermatic 200

              Millermatic 350P with Python
              XMT 304 /w S-64 feeder and 12VS
              Dynasty 300 DX
              Thermal Arc 400 MST
              Victor O/A
              Premier Power Welder for my trail junk.

              Comment


              • #8
                Millermatic 90

                I had a Millermatic 90 that did the same thing. I sold it as is.
                Good Luck,
                Bob
                Millermatic 252 w/30A
                Big Blue Air Pak
                Ellis 3000 Band Saw
                Trailblazer 302 Air Pak w/ Wireless Remote
                8-RC
                Dynasty 200 DX
                XMT 350 MPa w/S-74 MPa Plus
                Millermatic 211
                Passport Plus
                Spectrum 625 X-TREME
                Lincoln SA-200 Blue Tint Red Face '63
                2-Lincoln SA-200 Red Face '68
                SA-200 Black Face '59
                SA-200 Green Lite '84
                SA-200 Green Lite '80
                SA-200 Red Face '69
                SA-200 Red Face '66
                SA-200 Green Lite '81
                '70 Black Face Round Barrel

                Comment


                • #9
                  Thanks everyone for your replies. I am on travel this week, but I will try the component replacements when I get home.

                  Thanks
                  Jeff

                  Comment


                  • #10
                    Being away from my board right now... Does anyone know the original specs on Q1, Q2, and Q5 on this PCB?

                    Comment


                    • #11
                      Might be the Q1 component that caused simmilar problem on my mm135. here's the thread: http://www.millerwelds.com/resources...speed-too-fast

                      Q1 specs should be listed on the digikey link from my last post on that thread. At least you could google the component (2n6388).

                      If Q1 was already replaced, maybe they didn't use the right component?

                      Remember that unless you remove the component from the board for testing, you may not get an accurate test result.

                      I have the service manual if you would like a copy.

                      Comment


                      • #12
                        Turbo, would you mind sending me the service manual?

                        Thanks
                        Jeff

                        Comment


                        • #13
                          I've got a 135

                          I've got a 135, and am very sorry to glom on to your thread, but I can't figure out how to creat my own. My problem is the welder welds fine, right. Then the feed slows then will eventually stop, wait a minute generally and I can weld for a half to quarter of an inch. If I turn off the gass and unhook the drive tenssion lever a minute after this condition occurs, then pull the triger the drive wheel goes fine fully variable, and with a glove I can grab the wheel and try to stop it, and it still just keeps going. I release the trigger turn on the gas, apply the drive tenssion lever pull the trigger the wire feeds and feeds. I go to weld. Buzzzzz it goes then slows then will stop. Is there any place to start looking?
                          Thanks Ian

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