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miller 175 no wire feed and no weld output

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  • miller 175 no wire feed and no weld output

    Hi
    New to the forum but I have a millermatic 175 and I get gas but no wire feed or welding cabibilities. Checked the trigger and the TP1 (thermal OL) and they seem fine. Is there anything I am missing? Checked the relays on the PC board they are fine. I get no output from RC6 and RC7? Any suggestions would help me out. Thanks

  • #2
    There is a transformer internal to the fan motor that supplys 24Vac for the rest of the system, it may be pooched. however if it is pooched, there is no protection on the circuit board, so two traces are generally blown off it. These 2 traces pass from one side of the board to the other and simple to repair with a couple of 24 gage wires soldered from one side to the other

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    • #3
      cruizer thanks for the reply...I didn't check the 24VAC from the other half of the fan but the fan is still operational. I checked the board for traces blown apart but didn't find any maybe just not getting 24VAC. I will check RC2 and RC3 for voltage. Thanks i"ll keep you posted.

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      • #4
        Checked the fan and it has 24VAC. Does anyone know what the red LED on the board represents? It lights up when I depress the gun trigger. Does anyone know what CR1, CR2, and CR3 on the PC board do? They are relays but not sure what they do.

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        • #5
          Lets just see,,,,

          CR1 makes the motor go
          CR3 makes the gas solinoid go
          CR4 makes a path to the primary side of the weld coils

          So since all these relays come on with the activation of the trigger, best to verify the gun trigger terminals,ie, jumper the machine terminals #1 & #2 with a paper clip.

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          • #6
            Jumped the trigger input and still same results. The CR1 relay seems to activate and the other 2 relays don't. I wonder if CR1 is for the gas because the gas will flow but not the motor or primary side for transformer? I'm thinking something on the board has failed???

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            • #7
              All the relay coils must activate at the same time, as they are all together on the same branch, whether or not the output of these relays is working is anyones guess

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              • #8
                The LED just indicates that the trigger has been pulled and the relays should be turned on. The relays are all wired together and are powered by the trigger.
                Try tapping CR3 &4 and see if the welder starts working again. Then figure a way to test the contacts and see if they are closing. Both have to work in order to get weld voltage. Cr 3&4 supply the power to the weld voltage control circuit. ( works like a light dimmer). Need to get weld voltage before you will get wire drive. Weld voltage is used as the power supply for the drive motor. Just be careful, the contacts on these relays have 240 volts on them and hurts if you get tangled into it. For testing with an ohm meter you can disconnect the 240 vac from the pcb and tape up the wires. See the diagram pasted on the welder cover.
                Last edited by ccawgc; 06-19-2011, 10:03 PM.
                Glenn 300 amp stick
                Millermatic 35
                L-tec plasma

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                • #9
                  Yeah I took out the PC board and threw 24Vdc to all relays and they all triggered and all contacts OHM out correctly. I can try checking it in the welder and follow the traces for the relays see if any traces are bad or components.

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