Miller Sync 250DX no high frequency
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  1. #1

    Miller Sync 250DX no high frequency

    Hello, having trouble with serial LE386698.

    Symptoms are as follows

    - will DCEP stick weld just fine
    - will DCEN Tig weld once the arc is started just fine
    - to start the arc I have to go full pedal and tap the tungsten on the bench, once the arc has been started like this I can move over to the workpiece quickly and start the arc again to weld.

    I looked at spark gaps and set to 0.012" per the sticker and manual, I don't think these were off. I looked at CB-1 per the manual and its reset. The 120vac outlet next to it powers the water cooler and the paddle wheel is spinning rapidly.

    This is in a plant maintenance shop and gets occasional use, definitely not every day.

    I found some mention of CR - control relays but this machine doesn't have any relays on the wiring diagram.

    I would greatly appreciate your help or ideas to help troubleshoot and repair the machine back to normal operating.

    Thanks! - matt

  2. #2

    Re: Miller Sync 250DX no high frequency

    So....some more time with the welder and I think I might have a bad connection somewhere. The arc will start in tig at almost any starting amperage but it takes about 6 seconds for the arc to start after I step on the pedal. Worked on the welding table itself, shined up the pad where the ground connection goes, did some light filing of the clamp, checked the lugs on the main welder were OK and tight. Wondering if I could have damage to the water cooled jumper wire that goes out to the torch itself....

  3. #3
    Join Date
    Dec 2010

    Re: Miller Sync 250DX no high frequency

    Did you check your ground circuit?
    Weld like a "WELDOR", not a wel-"DERR"
    MillerDynasty700DX,Dynasty350DX3ea,Dynasty200DX,Th ermalArc400GTSW,LincolnSW2002ea., MillerMatic350P,MillerMatic200w/spoolgun,MKCobraMig260,Lincoln SP-170T,PlasmaCam/Hypertherm1250,HFProTig4ea,MigMax1ea.

  4. #4
    Join Date
    Mar 2010
    Ceres, California

    Re: Miller Sync 250DX no high frequency

    Check your pre flow gas setting. Might be set for 6 seconds.
    If you get gas with remote turn on and HF fires 6 seconds later. Its preflow timer.
    Check your owners manual on how to adjust.
    With a spark gap of 0.012, tells me you have the small points spark gap. They are know to fail.
    Miller doesn't sell that holder any more. you get a kit that takes you back to the larger points and set them to 0.008.
    See a lot of them fail by carbon track. they start smoking.

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