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Handler 135 wire feed - not

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  • Handler 135 wire feed - not

    I may have the same problem described by CNRTC with his Handler 175. I have Handler 135 I bought 6 or 7 years ago. It has about 50 hours on it. Stock# 500414,.. Serial# LA042944.

    A few days ago it started feeding erratically, then yesterday it stopped feeding altogether. When the trigger is pulled (even with no wire loaded), you can see the motor start to turn, but only turns a degree or two and stops.

    I pulled the leads off the motor and hooked them up to a multi-meter. With the power on and the trigger pulled it shows about 5 vdc. How much voltage is supposed to go to that wire feed motor?

    I can see a PTC1 and PTC2 on this board. They look like ceramic capacitors. The PTC1 has WI2J printed on it. Per your suggestion, I shorted out the leads on PTC1. I gently trimmed away a little bit of the insulation on the legs where they go into the circuit board and placed the end of an insulated screwdriver on the two bare areas. It made no difference when the trigger was pulled.

    Is it possible that I have a PTC1 problem too?

    Any other ideas?

    Thanks for any info.

    Gyrobob

    rwrominger***@***yahoo.com (remove the asterisks)
    Last edited by Gyrobob; 11-19-2007, 09:01 PM. Reason: clarity

  • #2
    The other possible problem is the motor drive transistor, Q1. This is probably a 2N6388 transistor which can also be found on www.digi-key.com. Most of the earlier boards had this transistor with the TO220AB package. The later boards had a TO 247 packaged device.

    You can find the spec sheet for the device on www.onsemi.com by searching on 2n6388.

    You can also give the service techs a call on the toll-free technical support number.

    Darrell

    Comment


    • #3
      Does the 5vdc at the motor leads mean anything? What is that voltage supposed to be?

      Is there anything I can measure to verify if it is the motor drive transistor?

      Is there any kind of voltage (maybe 12vdc from a battery) I can apply to the motor to verify if it is working?

      Thanks for your timely response and your expertise,

      Gyrobob

      Comment


      • #4
        Measure the output voltage at the output terminals. The WFS pot commands the control to provide a percentage of the weld voltage to the motor. For example, if the output voltage at open circuit voltage is 27 Vdc (tap 4) and the WFS pot is set to 50%, the motor voltage should be approximately 13.5Vdc (I say approximately because realistically there are some losses such as diode drops which will cause the voltage to probably be around 12 Vdc). Another impediment to getting a good voltage reading at the motor is the electrical noise that it generates. You still should be able to see the voltage change relative to the dial setting.

        One failure mode of these transistors is for one of the internal transistors in the Darlington pair to fail, which greatly reduces the gain of the transistor. The end result is a very slow running motor with not much torque.

        I mentioned in my earlier post that the transistor is most likely a 2N6388 which is in a TO 220AB package. If the device is in a larger TO 218 package (later boards), the part number is a TIP 142.

        Hope this helps.

        Darrell

        Comment


        • #5
          I'm not near the welder at the moment. How can I tell if I have a TO220AB or a TO218? Is it printed somewhere on the board?

          Thanks,

          Gyrobob

          Comment


          • #6
            The TO-220AB case style is smaller than the TO-218 case style. Do a Google search for "TO-218 case" or "TO-220 case" and you will get pictures of each. They are similar in appearance, just different sizes. The leads on the TO-218 case are separated farther apart than on the TO-220AB. Hope this helps.
            CW
            Hobart Handler 135
            MM 210
            Lincoln AC 225 Buzz Box
            Lincoln Ranger 10,000
            Jack of all trades, master of none; therefore Broke!

            Comment


            • #7
              I forgot to add that it is possible to apply 12 VDC to the motor to see if it will work. This is what the Hobart techs told me some months back when I thought I was having problems.
              CW
              Hobart Handler 135
              MM 210
              Lincoln AC 225 Buzz Box
              Lincoln Ranger 10,000
              Jack of all trades, master of none; therefore Broke!

              Comment


              • #8
                I just put 12vdc on that motor and it spins around enthusiastically.

                The circuit board assembly has 195 886 printed on it. There are two transistors on it. One, at Q1 has a heat sink. The other at U1 is by itself. They are both .4" wide. Which transistor are we talking about? The one on the heat sink has some sort of glue over it which is covering up the printing so I can't tell if it says 2N6388 on it or not. Based on pics from the internet, it looks more like they are the smaller case transistors, but I'm not really sure.

                Thanks for helping.

                Gyrobob

                Comment


                • #9
                  If the part number is TIP142 for the transistor in the larger TO 218 package, what is the part number for the transistor in the smaller TO 220 package?

                  Does Radio Shack carry these transistors?

                  thanks for any info

                  Gyrobob

                  Comment


                  • #10
                    A good place to get these parts are www.digi-key.com.

                    A good place to look at the spec sheets are www.onsemi.com.

                    The spec sheets will describe the package style.

                    The part number for the TO 220AB part is 2N6388.

                    The larger TO 218 part is TIP 142.

                    The TIP 142 has higher current and voltage ratings. Even if your board has the 2N6388, with a little creative lead bending and trimming, the TIP 142 will fit. That's how I originally tested the larger device prior to laying out a new board.

                    Darrell

                    Comment


                    • #11
                      Another place for parts is www.mouser.com . Also unless I'm wrong your motor uses different voltage for different speeds depending on what wire speed setting its on. You should also check that when you get a chance. This information should be in a maintenance manual that you can probably get for a few bucks from Miller. I had a similar problem once and it was the motor. Yours definitely sounds like a control supply voltage problem. Have fun you'll feel great after trouble shooting it and fixing it. Half the reward is from the journey. Uncrichie.

                      Regardless of which compnant you find at fault, check a few others on both sides of that one. Its not odd for a few componants to go at the same time.
                      Last edited by uncrichie; 11-21-2007, 04:14 PM.

                      Comment


                      • #12
                        Which transistor? Heat sink or plain?

                        The 2n6388s have arrived.

                        Which of the two transistors on the board do I need to replace? The one with the heat sink or the naked one?

                        Thanks,

                        Bob

                        Comment


                        • #13
                          I'm assuming the 2N6388 is the one with the heat sink, so it'll be a pain to replace. The heat sink and the 2N6388 are soldered to the board in six places, and the heat sink is riveted to the 2N6388.

                          Can I reuse the heat sink or do I have to get a new one?

                          Does the heat sink have to be soldered to the board for electronic functions, or is it just soldered there for solidity?

                          Thanks for any info,

                          Bob
                          Last edited by Gyrobob; 12-15-2007, 02:33 PM. Reason: irreverence

                          Comment


                          • #14
                            Don't try to unsolder the heat sink, you'll find that pretty difficult as it works just as the name implies, it sinks heat and small soldering irons don't work well.

                            Snip the transistor leads of the bad device.

                            Drill the rivet out to remove the transistor body from the large heat sink. The transistor is labeled Q1.

                            Unsolder the lead stubs still soldered in the board.

                            Insert the new device and solder the leads.

                            Attach the transistor to the heat sink with a nut and bolt.

                            Comment


                            • #15
                              PTC1 part number

                              I have a 135 Hobart Handler. I was told by someone that I needed to replace the PTC1 capacitor. I went to the local welding shop and they gave me one that was a little bigger. The part number on it is RX185 7153S. Unfortunately the old one got thrown away. The change out did not make the motor work. I would like to get the original PTC! back in My board number is 195886 my Q1 part number is 2n6388 as a reference. Can any one tell me the correct partnumber for the PTC1? Does putting a RX185 7153S work or do I need to go back to the original?

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