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I need help troubleshooting a 330a/bp

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  • I need help troubleshooting a 330a/bp

    I just bought a 1985 330a/bp welder. It looks like brand new. Anyway, it didn't have a foot control or tig torch, so I bought a new foot control from Miller. It is the correct one with the two prong twistloc and the three prong twistloc connectors. I also bought a new air cooled torch. I got everything hooked up and now I can't get any hi freq on the start only posiition. I do get hi freq in the continuous position. I can get an arc in the start only position by scratching it and then it welds. So everything works except the start only hi frequency. What should I check? Any help would really be appreciated.

  • #2
    Since you are getting HF in continuous, the fix should be easy/cheaper than harder. I have attached an image of a section of the circuit diagram and it is highlighted in yellow and green.

    The yellow section shows how the open circuit voltage is tapped off by variable resistor (R2) and then rectified to DC by SR2 and finally the DC voltage is applied to control relay CR1. If this relay is not moving when you turn OCV, you need to check this circuit.

    The green section just shows how the 115 VAC for the HF transformer passes through the S3 start/continuous/off switch. You could have an open/dirty contact in this switch not allowing the 115 VAC to get through and to the HF transformer.
    Attached Files