Millermatic 250X no power in gas solenoid circuit
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  1. #1

    Millermatic 250X no power in gas solenoid circuit

    I'm trying to repair an older MM machine I picked up, a 250X which is the version with digital voltage and wire feed controls. It welds but I've got no power at the gas solenoid. I've checked the leads with a multimeter and put in a known working solenoid off another machine so I know it's not the solenoid itself. It might be the board which I think would basically make the machine not worth fixing but I'm hoping there's a simpler explanation. As I understand it these machines have a converter that puts out 24VAC for the gas solenoid, wire feeder, etc. Could it be this converter? I'm not great with AC and I'm not sure where to test to see if this is working

    The manual is here: https://www.millerwelds.com/files/ow...O1320G_MIL.pdf
    Electrical Diagram is page 31

    The solenoid is run off RC6-3 and RC6-7 from the board with wire 3 going to the power supply but I'm not sure what the power supply actually looks like and not sure how to test it with my meter. Would I trace wire 3 to the power supply and then put my meter leads on wires 3 and 7 looking for 24VAC? Is it safe to assume that with the welder powered up that will always be producing 24V?

  2. #2
    Join Date
    Oct 2014
    Posts
    93

    Re: Millermatic 250X no power in gas solenoid circuit

    The 24 volt is supplied by two seperate transformer secondaries.
    Test between 3 and 7 for 24 volt and 4 and 8 for 24 volt at plug plg1/plg 2

  3. #3

    Re: Millermatic 250X no power in gas solenoid circuit

    Quote Originally Posted by danielplace View Post
    The 24 volt is supplied by two seperate transformer secondaries.
    Test between 3 and 7 for 24 volt and 4 and 8 for 24 volt at plug plg1/plg 2
    Thanks! Will do.

  4. #4

    Re: Millermatic 250X no power in gas solenoid circuit

    Quote Originally Posted by danielplace View Post
    The 24 volt is supplied by two seperate transformer secondaries.
    Test between 3 and 7 for 24 volt and 4 and 8 for 24 volt at plug plg1/plg 2
    Well I am getting 24VAC (actually 26V) on both those secondaries. I'm also getting a voltage at the solenoid wires which varies between 4-8VAC and is present whenever the welder is on. This voltage varies a bit but it doesn't go up or down when I press the trigger.
    Thoughts? I'm not sure where to go next.

  5. #5
    Join Date
    Apr 2017
    Posts
    370

    Re: Millermatic 250X no power in gas solenoid circuit

    Gas Valve GS-1 is controlled by Circuit board PC-1.
    You are correct in testing 3 & 7 as well as 4 & 8.
    On PC-1 there are a line of pin connectors running down its side , look for connector RC-6 (bottom).
    On RC-6 look for pin number 3, left side second from the top, if I remember right.
    That pin feeds wire 8 that goes to your gas solenoid and should read 24 VAC across the gas solenoid with trigger depressed, note will not be present when triggered from spool gun when connected to receptacle RC-7.
    Check for any loose connections at RC-6, low voltage could very well be a loose connection within GS-1 circuit.
    If AC voltage is still low when tested at RC6 ,pin 3 to wire 3 with trigger closed then PC-1 could be a concern.

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