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Need help with AMT304

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  • #16
    Have you tried the lift start? I can't remember off the top of my head if that is a 7V or 15V circuit. Put it in lift start and jumper the A and B in the remote socket. Of it's 7V, something tells me your arc sensing circuit isn't working right.


    • #17
      Sorry for not replying... I've been really busy lately, and haven't had time to dig up a schematic and think about it.


      • #18
        Can you list out what/where the tech already had you check?

        It seems like since it works when you override the contactor circuit in the electrode hot positions (VS, Stick), something may be preventing the contactor circuit from operating properly in stick and VS mode (same thing in all of the contactor on circuits? Did you try to jumper A and B in VS mode too? Does it work if you jumper A and B in all electrode hot positions (Lift Arc Tig, Scratch Start Tig)? I would first check to see if the contactor signal is dropping out when the voltage drops to 7V while you're welding (might need another person or a test jig, connecting your test leads and putting the case back on so you're out of the way of fragments if something goes).

        I would also recommend putting it in the mig position, jumpering A and B on the remote socket (should give you output power so the VS feeder works) and trying to mig that way - that should let you know if there is something wrong in the voltage feedback circuit.

        Also, measuring the voltage across pin H and pin D should let you know if the feedback circuit is working (voltage should be 1/10th the expected voltage - 0.7V at idle in lift arc; 8V at idle in Stick, VS, Scratch Start Tig; 1/10th of the mig voltage setting when you jumper A and B).

        Hope this helps.



        • #19
          Thanks. I will do this.