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  • MM 135 Wire feed issues

    hi guys, i have read a lot of complaints and possible fixes for the same complaint i have been having since i purchased my MM 135.
    the wire will decide on its own when it wants to feed wire. it happend almost right away when i purchased the welder many years ago, is only has about 2 hours of weld time on it. anyway i brought it back to the store and they tested it and said nothing is wrong with. still ever since it was new it has this problem.

    you start running a bead then it starts popping and the wire stops feeding.
    you run it open air and it either not com out at all or slowly comeout. if you let it run for a few seconds or pull on the wire then it will beging to feed correctly. this has made for some really nice looking welds. doesnt seem to matter if the housing is kinked or twisted. new tips and new wire have been tried. It seems to me like the motor is not getting sufficeint amprage or the drive motor has a dead spot in it. but yet it will run fine for a few minutes the act up. then be fine then act up. If you open the cover and watch the wheel it will turn and feed the wire just fine until it acts up then you try and help the roller along but that doesnt change anything either.

    thought about getting a new drive motor but from what i read is maybe i need to get this capasitor the is bolted in the bottom of the welder.

    ask me some more questions or shed your thoughts.

    i dont weld that often but when i do i want the **** thing to work.

  • #2
    There are two likely culprits that may be causing the problem that you're describing and they're both on the control board.

    One has the designator PTC1. It's a flat, disc-shaped device. You can find a replacement at http://search.digikey.com/scripts/DkSearch/dksus.dll.

    This device is a PTC resettable fuse rated at 1.85A (hold), 60Vdc.

    The other possibility on the control board is The power transistor Q5. This is a 2N6388 in a TO-220AB package. Here's a replacement: http://search.digikey.com/scripts/Dk...eywords=2N6388

    Other potential causes:

    - kinked gun liner
    - wire slipping at drive roll
    - worn wire inlet guide in feedhead
    - brake nut too tight on wire spool hub
    - tension arm too tight on feed head

    Try investigating the non-p.c. board items first (bottom list).

    Comment


    • #3
      Ive had the same problem a couple times. Both times it was something different. 1st time I had this problem it was the liner in the gun lead. I had to replace the liner and it fixed it. The liner that was bad was on a new welder. I had not even run 15 minutes. Seems crazy but these things do happen even on new units. The other time I had this problem it was the roller. The wire feeds in then crosses the roller before entering the liner on the out. That roller has a small groove that the wire has to ride in. For some reason my wire would ride and then at random times it would "jump the track," if you understand that. It would come out of the groove but not really all the way. Just enough that it would not grab and move any further. To remedy that I just had to kind of straighten the flexible pieces that the wire come out of before it hit the roller and entered when leaving the roller so that the wire fed straighter and then readjusted the tension on the roller and problem was solved. If none of this helps and any other tips someone may have then go to the board as directed above in last post. Good Luck and let us know how it comes out but definately get it fixed. Its to good of a welder and money in it to let it hang around unfixed by a probable small thing and you will definately feel better to use it more often if you know it is working right rather than put it off till later.

      Whitey
      Whitey
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      Comment


      • #4
        Exactly the same description of my problem. I first replaced the Q1 on the board without results and then changed PTC1 with great success. See my earlier posts on this problem. Good Luck

        Comment


        • #5
          Pct1

          thanks for all the respnce's

          is there a thread for completing this repair?

          is there any photos of where this is located?

          ill take pictures and post a write up upon this repair fixing my welder.

          Comment


          • #6
            I believe that you can find the PTC1 part number on one of the threads and you can order it from Digi-key - I think less than a buck. Now, you'll need to remove the circuit board by disconnecting several input leads (I marked my leads according to their respective board number) and then you'll see how the boards releases and pulls out. You'll see PTC1 printed on the board beside its respective component. Desolder the old one and solder in the new one. Put it all back together and give it a try. I don't have pics but I think it will be obvious once you tear into it. If you don't have a soldering iron, borrow one or go to radio shack and get their cheapest one, it will come with a very small roll of solder. Don't use a torch. I hope this helps!

            Please post back and let us know if this works or not as it really helps to round out these problem solving threads!

            Comment


            • #7
              Originally posted by Hobart Expert Darrell View Post
              There are two likely culprits that may be causing the problem that you're describing and they're both on the control board.

              One has the designator PTC1. It's a flat, disc-shaped device. You can find a replacement at http://search.digikey.com/scripts/DkSearch/dksus.dll.

              This device is a PTC resettable fuse rated at 1.85A (hold), 60Vdc.

              The other possibility on the control board is The power transistor Q5. This is a 2N6388 in a TO-220AB package. Here's a replacement: http://search.digikey.com/scripts/Dk...eywords=2N6388

              Other potential causes:

              - kinked gun liner
              - wire slipping at drive roll
              - worn wire inlet guide in feedhead
              - brake nut too tight on wire spool hub
              - tension arm too tight on feed head

              Try investigating the non-p.c. board items first (bottom list).
              Darrell,

              I have a Millermatic 175 that wants to feed in high speed only. The WFS pot measures 0-50K and is working correctly. Do you think the above 2 parts will fix my problem?

              Thanks,
              Charles
              Millermatic Passport Plus
              Millermatic 200

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

              Comment


              • #8
                Originally posted by crawler View Post
                Darrell,

                I have a Millermatic 175 that wants to feed in high speed only. The WFS pot measures 0-50K and is working correctly. Do you think the above 2 parts will fix my problem?

                Thanks,
                Charles
                From a post of his in another thread, sounds like it could be the transistor...

                http://www.hobartwelders.com/weldtal...ght=feed+motor


                Originally posted by Hobart Expert Darrell View Post
                You won't measure much of a voltage at the base of Q1, as the transistor is a current controlled device. You'll only be able to measure the junction voltage as it's being switched.

                If you want to check the function of the 555, it would be best to have an oscilloscope connected to the anode of D8 which is connected to pin 3 of the 555. If you have a DMM connected to the anode of D8, you'll still be able to see the RMS or average value (depending on DMM type) of the switched waveform change as the wire feed speed control potentiometer is varied.

                If you determine the 555 to be functioning, the problem is most likely Q1. It's a Darlington pair transistor, so the failure modes can either be shorted (motor runs with no speed control), open (motor doesn't run), or one transistor of the pair damaged (motor runs slow due to low transistor gain).
                For your information, the output of U2 (555) drives the transistor (Q1) through D8, R4, and R15.

                Comment


                • #9
                  Originally posted by crawler View Post
                  Darrell,

                  I have a Millermatic 175 that wants to feed in high speed only. The WFS pot measures 0-50K and is working correctly. Do you think the above 2 parts will fix my problem?

                  Thanks,
                  Charles
                  It's the transistor. It's shorted. It's a Darlington pair and the second stage is shorted.

                  Don't replace the PTC.

                  You can replace the 2N6388 directly, or if you want to put in a more robust transistor, replace it with a TIP142. This is a larger packaged device (TO-247), so you'll have to bend the leads a bit to make them line up with the hole pattern of the 2N6388 which has a TO-220AB package. The leads of the TIP 142 are also thicker, so you'll need to file them down slightly to allow them to be inserted into the board. The TIP 142 will still fit the heat sink. The defective device is rivoted to the heat sink. Just drill the rivot out and use a bolted connection for the replacement device. If this is too much hassle, just make a direct replacement with the 2N6388.

                  Darrell

                  Comment


                  • #10
                    Originally posted by Hobart Expert Darrell View Post
                    It's the transistor. It's shorted. It's a Darlington pair and the second stage is shorted.

                    Don't replace the PTC.

                    You can replace the 2N6388 directly, or if you want to put in a more robust transistor, replace it with a TIP142. This is a larger packaged device (TO-247), so you'll have to bend the leads a bit to make them line up with the hole pattern of the 2N6388 which has a TO-220AB package. The leads of the TIP 142 are also thicker, so you'll need to file them down slightly to allow them to be inserted into the board. The TIP 142 will still fit the heat sink. The defective device is rivoted to the heat sink. Just drill the rivot out and use a bolted connection for the replacement device. If this is too much hassle, just make a direct replacement with the 2N6388.

                    Darrell
                    Darrell,

                    Any idea where this transistor is located? I've attached the pic of the control board.

                    Thanks,
                    Charles
                    Millermatic Passport Plus
                    Millermatic 200

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

                    Comment


                    • #11
                      Here is the pic of Q5 location on Miller part # 207466 (control board for MM 175)
                      Millermatic Passport Plus
                      Millermatic 200

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

                      Comment


                      • #12
                        I got the parts in from Digi-Key today. Got the Darlington pair transistor and desoldering braid.

                        Item: 497-2541-5-ND
                        Description: TRANS NPN DARL 100V 10A TO-247
                        Price: $1.74

                        Item: 473-1064-ND
                        Description: DESOLDER BRAID RMA FLUX .125" 5'
                        Price: $3.54

                        Shipping was around $2.00
                        Millermatic Passport Plus
                        Millermatic 200

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

                        Comment


                        • #13
                          Repair pics. First pic is location of Q5. Second pic is removing the original transistor. Last one is of TIP142 installed. I used thermal grease and aluminum rivet since I did not have a small machine screw to clamp the transistor. The most time consuming part was filing and bending the legs on the TIP142 transistor to get it to fit.
                          Last edited by crawler; 05-05-2010, 03:04 PM.
                          Millermatic Passport Plus
                          Millermatic 200

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

                          Comment


                          • #14
                            Darrell, myjeepsbigger,

                            Thanks for your help. The welder works now.

                            Charles
                            Millermatic Passport Plus
                            Millermatic 200

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

                            Comment


                            • #15
                              Very nice!!

                              Comment

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