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Big Blue 400 Pro No Weld

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  • Big Blue 400 Pro No Weld

    Hi, I am new to this forum. We bought a 400 Pro and had it in storage for a while and only recently took it out to do a bit of welding. It has power at the outlets but it just won't weld. If you switch it over to the gouge settings, it will give a little spark but nothing. When it is in either xx10 or xx18, the voltage would drop from 30 volts to zero and stay at zero after you remove the electrode from the work. What is the possible cause for this to be happening?

  • #2
    If it has been sitting for a long time make sure the brushes are not stuck and are making a good connection. And a serial number would help since there is 12 models of the BIG BLUE.


    • #3
      sounds more like its in one of the lower remote settings. Just cause the unit may have a remote, don't place the mode dial in remote.


      • #4
        There is not a separate remote switch on this unit. You can take a snapshot of the summary file. If you have a USB stick put it in the USB port and start it up.
        Each time the USB is inserted it will give you a summary file "USB ACC" will display. As the file is written when the display no longer displays
        "USB ACC" the process is complete. Try this it might help diagnose the problem.


        • #5
          Sorry about the late reply. I was waiting for the email notification which I didn't get. The brushes are ok, it is in the always on settings. The serial number is MH210261R. We do not have a USB stick to get the information from it.

          We are getting 50ac volts on each of the wires that comes from the coil to the rectifier. It is converted over to DC volts and gives 72dc volts and goes to a board that has two big capacitors on it. When VRD mode is enable, 30dc volts is outputted. As soon as you disable VRD mode, 0dc volts is outputted but the 50ac volts and 72dc volts remains on the input side of that board that has the two capacitors. Is something wrong with that board or the main board?


          • #6
            Three possible issues come to mind...

            1. Try unplugging the Hall Device (blue current feedback device) at the device. Only see if your normal Open Circuit Voltage comes back, do NOT weld with it unplugged. Normal OCV will be about 70-80 VDC.

            2. The PC1 board is not powering the IGBT boards, or not gating the IGBT boards. RC2-1 and RC2-9 = +15VDC in reference to RC2-3, RC2-2 and RC2-10 = -10VDC also in reference to RC2-2...... Gating signals measure RC2-4 and RC2-12 each in reference to RC2-2 and should measure -10 VDC in Output OFF mode and +15 VDC in Output ON mode.

            3. If those all measure correct, the IGBT modules would need replaced.


            • #7
              It is a lot more simple to check the 3 LED'S on the IGBT mods. green LED1 is on the far right lit when the 18 volts DC is present green LED2 far left lit when -9 volts is present LED3 lights orange when PWM signal is present indicating that weld contactor is on. Both Mods should have these LED'S.
              No meter needed to test this they are kind of hard to see i use a mirror. If the green LED'S don't come on the PC1 is bad. Also it would throw an error code if either of the MOD's are open or shorted.


              • #8
                I don't know why I am not getting the email notification. Thank you blue_tech and WELD dr. Miller did reply and it was the main board that was causing it not to weld. There was only 1 green light ok each IGBT boards. We got the replacement board this week and it is welding now.
                The weird thing now is when we are welding, Oil 0249 would display and the welding would stop until the voltage and amp display comes back on.


                • #9
                  If the board loses the Engine Speed Feedback, the board will display status items as if you di not start the engine and are just trying to see the oil change hours for example. I would expect that is where your issue is, but if it is a loose wire connection or something else, you will have to figure that out. It is Wire Cafe' Racer Style Motorcycle Frame & Jig Plans that feeds from the circuit breaker CB8 and goes to the board at RC4-4. You should measure 24 VAC, which the board uses to identify the engine speed by frequency measurement.