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Syncrowave 300 unstable high range current troubleshooting

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  • Syncrowave 300 unstable high range current troubleshooting

    Sorry for the long first post, but a strange problem has recently developed with my mid 80's vintage Syncrowave 300 welder.

    In low current range the welder behaves perfectly fine, AC works well, HF works, pulser works, current output is linear and smooth. When I switch it to the High range it is basically wide open. It outputs close to 300 amps I would estimate (vaporizes 3/32" tungsten) and there is no throttle control either using the foot pedal or the panel control.

    So I took some readings from the output of the hall effect sensor, Pin 87, and found the output voltage is approximately correct in the low range, but is wide open in the high range. OCV is also right at 79.5 volts and seems about right while welding.

    Here are some average values - in low should be -1 volt per 20 amps and in high -1 volt for 100 amps

    20 amp dial = -1.2v
    40 amp dial = -2.3v
    60 amp dial = -3.5v
    75 amp dial = -4.3v

    100 amp dial = -4.4v
    250 amp dial = -4.5v

    So to me this proves the LEM is working properly and the problem is exclussive to the high range. I checked out the schematics and it looks like the only difference is the low range reactor and turns through the LEM core.

    Has anyone seen anything like this before or have any theories on what could be going on?


  • #2
    Spoke with Robin from Miller Tech dept. (who was very helpful) and it appears the high range cable is in the wrong direction through the toroidal core of the hall effect sensor. I may have done this when I cleaned all the contacts a year or so ago, but I thought I was careful putting it back together. I never use the high range, so who knows when this was reversed.

    So if anyone has this problem in the future, the symptoms are slightly elevated low range output that is controlled ok, and an uncontrolled high range output.