Cigweld 400SP wire feed speed out of control

  1. TommyB New Member

    Messages:
    6
    Location:
    Hobart, Tasmania, Australia
    G'day everyone, I bought a second hand mig welder about a year ago which has turned out to be quite a nice machine overall but it has this one issue where it just all of a sudden starts feeding the wire out as fast as it possible can? It's usually a pretty rare occurrence so I haven't been able to pinpoint any reasons for why it might be starting sadly. I've taken it into the shop to get them to see if they can work out what the go is but of course the machine is working perfectly on there now so I thought I'd come here for some ideas.

    So you could be welding away just fine and then all of a sudden the wire will just feed out at maximum speed. It could happen twice in an hour or you could go for weeks without any issues and the only way I've found you fix it is to do a full reset of the machine which then only works maybe 70% of the time so I just have to keep going until it sorts itself out? So this is the welder and wire feeder below if that helps anybody? I know it's going to be hard to pinpoint what the issue is but I'm hoping somebody has had the issue before and can point me in the right direction

    Thanks very much for your time, Tom
     
    • Screenshot_20200524-084351_Gallery.jpg
  2. eddie49 Member

    From the nature of the fault as you have described it, and the frequency that it occurs, I would guess that this is a contact problem on or near the printed circuit board ( PCB ) that controls the motor speed.

    Is the machine very old and dirty, does it get used in a dirty environment? If so, it might be good to start with a good external & internal clean-up, with a vacuum cleaner, compressed air blow-gun, and brush.

    I have never worked on a machine with a separate feeder, but I would assume that it is a self-contained unit, with its own power supply, control board, front panel controls, and the motor. Do you set the desired speed digitally, or with a traditional potentiometer ( pot )? If the latter, the fault could be one of the three "legs" of the pot loosing contact, either internally or the wires that link the pot to the PCB.

    Can you get the feeder to run all by itself? I mean, no welding power source, no gas, no MIG wire, just the power cable for the feeder, the Euro torch, and the front panel speed setting? If so, open up the case, get it running ( i.e. press and hold the torch trigger, or use 2T/4T to set it running continuously ) so the motor just spins away, without actually feeding wire. Then start probing, pushing and pulling everything inside. ** Take care, there will be live mains voltages inside - but the motor and PCB may be low voltage DC anyway. Use a plastic rod or a wooden dowel to press and probe all connections, plugs and sockets. Use an insulated tool to wiggle all the wires, especially at termination points. Finally, press on individual components on the PCB, and on the underside ( the solder side ). A component may have a broken lead, or a dry joint, or a copper track on the PCB may be cracked. If you can succeed in provoking the fault by these actions, you will hear the motor speed up.

    If that does not help, then power off, dismantle the feeder so that you can remove the PCB(s ). First, note where all the connectors go. Then use a bright light and a magnifier to examine all the solder joints on the board(s). Re-solder any that look "dry" or suspect. Also check for loose blobs of solder - or even grinding dust or metal swarf - that might be causing intermittent short-circuits.
     
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