SIP Weldmate P178 inverter, HF start not functioning

  1. kevshouse New Member

    Messages:
    5
    Location:
    Devon UK
    Hi all,

    I am faultfinding this P178, seems to scratch start OK, but I can't get the High Frequency to activate. So far, all I have done is clean the spark gap, (currently set at 1mm). Ideally, I would like to see a copy of the circuit diagram so that I can work in a logical fashion.
    Therefore, if anyone can post a diagram and or offer any sage advice concerning these boxes, I'd be thoroughly chuffed.
     
  2. Mark 2 Member

    Messages:
    45
    Location:
    London UK
    I have one of these, definitely didn't come with circuit diagram so can't help you there. How do you tell if the HF start is. not working?
     
  3. eddie49 Member

  4. kevshouse New Member

    Messages:
    5
    Location:
    Devon UK
    One can tell if the HF is functioning by placing the tungsten a few mm from a workpiece and pulling the trigger. At this point, one should hear the gas solenoid pick, and also see an arc flash. I didn't get anything, so I assume there's a fault.
     
  5. kevshouse New Member

    Messages:
    5
    Location:
    Devon UK
  6. kevshouse New Member

    Messages:
    5
    Location:
    Devon UK
    Aha, aced it!
    I found the fault, well, two actually. The HF spark generator is a small board mounted on the bottom deck of the chassis, just behind the output terminals. One has to remove the terminal bus bars (zinc-coated brackets) to get at the HF. The fault in my case was that some impact wobbled the flyback transformer, breaking the plastic base and severing the secondary windings at the point where they are soldered to the output pins. I desoldered the transformer and found that I could simply glue the plastic back together. Once glued, I resoldered the secondary and reinstalled the tranny back onto the PCB. Satisfied with my repair, I prodded about the rest of the machine, just in case there was further damage, there was none. But I did find one of the filter capacitors on the main power board at the front had only one leg soldered, the other was just resting on the PCB! Somehow, I don't think these machines go through much of a quality check.
    I've tested the box, HF working fine and Tiging like a champ!
     
    Mark 2 and eddie49 like this.
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