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Handler 140 erratic wire speed problem

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  • Handler 140 erratic wire speed problem

    My first time in this forum, hi all!

    I have a Handler 140 that is just over 3 years old. It's not heavily used, maybe once a month, and only with 0.030" flux core wire. A couple of months ago the wire feed began varying erratically, it would speed up, slow down, occasionally stop and then start again. I went through all of the things that are recommended but nothing helped. Last weekend I tried a new test, I released the wire roller tension and ran the feed motor with no load on it, and it still ran erratically!

    This seems to be pretty conclusive, there is a problem with the motor drive electronics. I've read a number of older threads here about problems with the circuitry on the drive board, but none of those quite matched the symptoms I have. So I thought I'd ask the experts first about the issue. Where should I look for the problem? Is this likely to be the main drive transistor, or something else?

    Note I have not tried measuring the voltage at the motor because I don't think that would tell me anything new. The fact that the motor will at times run normally says to me that the motor is fine. I can't imagine a motor failing in a way that would cause it's no-load run speed to vary erratically given the same voltage.

    Thanks!

    Bob

  • #2
    Originally posted by Bob4242 View Post
    My first time in this forum, hi all!

    I have a Handler 140 that is just over 3 years old. It's not heavily used, maybe once a month, and only with 0.030" flux core wire. A couple of months ago the wire feed began varying erratically, it would speed up, slow down, occasionally stop and then start again. I went through all of the things that are recommended but nothing helped. Last weekend I tried a new test, I released the wire roller tension and ran the feed motor with no load on it, and it still ran erratically!

    This seems to be pretty conclusive, there is a problem with the motor drive electronics. I've read a number of older threads here about problems with the circuitry on the drive board, but none of those quite matched the symptoms I have. So I thought I'd ask the experts first about the issue. Where should I look for the problem? Is this likely to be the main drive transistor, or something else?

    Note I have not tried measuring the voltage at the motor because I don't think that would tell me anything new. The fact that the motor will at times run normally says to me that the motor is fine. I can't imagine a motor failing in a way that would cause it's no-load run speed to vary erratically given the same voltage.

    Thanks!

    Bob
    How about a faulty thermistor, which could vary the voltage you refuse to check?
    Last edited by Northweldor; 11-08-2017, 06:24 AM.

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    • #3
      Originally posted by Northweldor View Post
      How about a faulty thyristor, which could vary the voltage you refuse to check?
      Do you know which component number is the thyristor? Replacement part number?

      You are right, I'm being lazy and jumping to conclusions, not good. I will test the motor voltage to confirm the diagnosis.

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      • #4
        Originally posted by Bob4242 View Post
        ...Note I have not tried measuring the voltage at the motor because I don't think that would tell me anything new. The fact that the motor will at times run normally says to me that the motor is fine. I can't imagine a motor failing in a way that would cause it's no-load run speed to vary erratically given the same voltage...
        I was assuming it's a voltage-controlled variable speed DC motor. Which means testing motor voltage under failure would tell you if it's the motor or the speed controller.

        I do agree that it is probably the speed controller.

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        • #5
          Originally posted by Bob4242 View Post
          Do you know which component number is the thyristor? Replacement part number?

          You are right, I'm being lazy and jumping to conclusions, not good. I will test the motor voltage to confirm the diagnosis.
          If you do a search on here, you will find many similar complaints. You can pin the problem down by jumpering the thermistor to see if the problem disappears. Check your manual for the component location, and a part source and number should also show up in your search.

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          • #6
            Welcome to the forum, Bob.
            Did you call tech support?
            Lincoln A/C 225
            Everlast PA 200

            Comment


            • #7
              Originally posted by MAC702 View Post
              I was assuming it's a voltage-controlled variable speed DC motor. Which means testing motor voltage under failure would tell you if it's the motor or the speed controller.

              I do agree that it is probably the speed controller.
              I will definitely do more testing. I read on another thread that the feed motor voltage is determined as a fraction of the arc voltage in some models, not sure if that applies to the 140 but if it does that means it could be the arc voltage that is varying. When the wire speed drops I lose the arc anyway so I wouldn't necessarily notice. I'll go at it again and test everything I can.

              Comment


              • #8
                Originally posted by M J Mauer View Post
                Welcome to the forum, Bob.
                Did you call tech support?
                Not yet, I checked out this forum and found an impressive amount of support so I thought I'd try getting advice here first. If I can pin it down to a component on the motor drive board I have no problem replacing that myself. The advice so far is that I need to be more thorough with my testing before making a diagnosis!

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                • #9
                  Originally posted by Bob4242 View Post
                  I will definitely do more testing. I read on another thread that the feed motor voltage is determined as a fraction of the arc voltage in some models, not sure if that applies to the 140 ...
                  I have serious doubts that it applies to any small CV machines like these. Ignore anything that isn't specific and verified to the model in question.

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                  • #10
                    Update on my problem. I now have an "it just magically fixed itself" situation (I really hate these). After opening the case and poking around inside today, testing voltages and such (everything A-OK), it refuses to screw up again. Feed and arc are steady and normal. The problem always was intermittent, but previously it would screw up about every other weld, and at least once it continued to screw up even after releasing the feed tension and running it with no arc and no feed. But now I can't get it to fail again. Maybe it was loose connections, or possibly dirty contacts on the voltage selector which I rarely change from position 3. During the voltage test I ran from 1 through 5 checking the open-circuit weld voltage (got 19V, 21V, 24V, 26V, and 28V). Maybe that's what fixed it.

                    Thanks for the feedback, I guess I won't worry about it unless it happens again!

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                    • #11
                      Just in case anyone is curious, here are the full results from my voltage test. The feed motor voltage range does vary with the arc voltage selector. I don't know if that means the motor voltage is tapped directly off the arc voltage or there is some parallel circuitry in the feed motor drive, but it does vary. In all cases the feed motor voltage was steady when the adjustment knob was not being moved, and it was all repeatable through 2 full test cycles.

                      Position 1: 19V arc, feed motor 2-16V
                      Position 2: 21V arc, feed motor 3-18V
                      Position 3: 24V arc, feed motor 4-20V
                      Position 4: 26V arc, feed motor 4-22V
                      Position 5: 28V arc, feed motor 5-23V

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                      • #12
                        There is a surefire way to get an intermittent problem to rear itself. Start an urgent emergency project using that machine on a Friday night.

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                        • #13
                          Bob, thanks in sharing the results from your voltage tests. Especially since I have been very curious in the voltages from the five voltage taps on my Handler 140
                          -John

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