Hede Nielsen mig welder

  1. Martini Member

    Messages:
    5
    Norfolk UK
    I have been using a Hede Nielsen Mig welder on and off for about twenty years. Suddenly it has started burning holes through 1.0/1.2 mm steel sheet when on its lowest setting. The arc looks and sounds more fierce than it used to. Any suggestions as to what has changed? Everything inside looks and feels ok (connections, switches etc) It has three large capacitors. Could one or more of these failing cause this?
    All suggestions welcome as I either need to fix it or buy a new welder.
     
  2. anto Forum Supporter

    Messages:
    788
    Location:
    Ireland
    Is it a gas or gasless welder?
    If its a gas welder then it sounds like you've run out of gas.
    If its gasless then I don't know.
     
  3. mike 109444

    mike 109444 Member

    Messages:
    4,087
    uk Bristol
    If caps not working then there would be LESS punch and your welds would be building up and lacking penetration.
    You might need to set machine to lowest setting and back off/flip off wire feed, then meter between the work ground clamp and the weld tip (meter set to DC volts) and see what voltage you are getting. Maybe step up through the range and note the readings.
    Could be you have a duff diode that's passing SOME AC through.
     
  4. mike 109444

    mike 109444 Member

    Messages:
    4,087
    uk Bristol
    Oh and welcome BTW :hug:
     
  5. Martini Member

    Messages:
    5
    Norfolk UK
    Thanks guys.
    Welder is a Hede Nielsen Euroboy 3. which I bought new many years ago.
    Gas Pressure gauges show ok and I can hear gas release.
    Capacitors all look good and it is good to know that they should not cause this type of fault.
    I will try to test the diodes to see if any have broken down.
    Welder has 4 power settings and is working fine apart from arc is too fierce even on lowest setting.
    I will try some voltage measurements.
     
  6. Martini Member

    Messages:
    5
    Norfolk UK
    Small update. Stripped out diode pack. 8 diodes on as 4 pairs on heat sink grid. All diodes test ok.
    Will take capacitor bank out next
     
  7. Martini Member

    Messages:
    5
    Norfolk UK
    Update:
    I have removed capacitor bank. Three 16000 uF capacitors in parallel which I presume add up to 48000 uF.
    Tested each capacitor with ohm meter. Two test as open circuit and show changing values as they try to charge.
    One fluctuates between open and short circuit. Retested all three with power supply and bulb discharge. Two will charge and discharge, the third will not.
    I bought 3 x 15000 uF capacitors from RS components and fitted them. Welder is once again ok with thin metal. So it seems that the smoothing from the capacitors is important in avoiding burn through of thin steel sheet. My guess is that one capacitor was failing by short circuit so effectively cancelling all of the capacitors. I have treated the welder to a new complete torch. I also purchased 4 new large diodes so at some point I will make a new diode bridge to try out.
     
    KemppiFrog likes this.
  8. mike 109444

    mike 109444 Member

    Messages:
    4,087
    uk Bristol
    Result :clapping: and good on you for posting results back on here :thumbup:
     
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