Electrical Fault Help? - Kemppi Minarc 180 Adaptive

  1. Dan The Welder Man Member

    Messages:
    15
    Location:
    Uk, Leicestershire
    Hi All,
    I was hoping you could help with a potential electrical fault. Apologies for the long post but I want to convey all the info I can.
    I have recently inherited the Kemppi Minarc MIG 180 Adaptive. I've not had it for long but it worked perfectly in automatic mode (not yet tried manual mode) up until today. I went to use it this morning and during a tack weld, the machine 'cuts out' and the wire feed stops. I squeezed the trigger and an intermittent and random ticking sound can be heard but no wire is feeding though the nozzle. I also noticed the overheating indicator light was on. It could not have overheated because I had only made a few tacks. After allowing 10 minutes to cool down the issue remains.
    My first thought was a potential issue with the wire feed motor - a loose connection somewhere maybe? I adjusted the wire feed speed (by adjusting material thickness in automatic mode) to its lowest setting and surprisingly the wire fed through the nozzle unlike before. Increasing the speed and the issue began again. Turns out the wire would only feed though the gun at slow speeds!? With wire speeds greater than approx. 3 metres/min, the intermittent ticking starts with no wire feed.
    I tried again, this time in manual mode and the wire fed at higher speeds right up to the maximum suggesting its not a motor problem!
    I therefore tried laying a weld down in manual mode and on immediate contact with the workpiece, the machine cuts out again and the ticking kicks in again. I noticed on contact, the wire would spark then immediately cut out leaving a glowing wire for a second or two fixed to the workpiece. When pressing the trigger with the wire fixed to the workpiece the usual ticking sound can be heard and no wire feed but there is also another internal electronic 'ping'. This only occurs when the trigger is on and the wire is in contact with the workpiece - when not in contact with the workpiece, just the ticking can be heard.
    I opened the machine up and on first impression nothing looks out of place, however I have not yet removed the main PCB as it is installed facing into the machine.
    Before I start looking at the electronics, has anyone come across this problem and know of a fix? Does this sound familiar or is this known to be a fault? Is there an obvious first place to look? The welder went from working fine to this problem the following day so I'm thinking a component may have failed?
    I'd really appreciate any feedback so that I can hopefully get this welder fixed.
    Happy to provide more info/ pics if that helps.
    Thanks, Dan
     
  2. eddie49 Member

    Unless you get lucky, DIY repair on an inverter machine with advanced automatic controls is not going to be easy. Assuming it is no longer under warranty ( ? ), you are still more likely to get a solution via the manufacturer - but probably at a high price. According to the Kemppi support contact list, Six Hills Welding Supplies Ltd. LE13 0RG are repair agents.

    The following people may be able to repair it:

    @Jim Davey

    These guys ( formerly Farnell/Gould/Advance switch-mode power supply designers ) offer to repair inverters:
    http://www.advanceproductservices.co.uk/index.html

    Welder repairs - inverters & transformer winding:
    https://www.specialistmachineparts.co.uk/welding-equipment-repairs

    The overheating indicator probably doubles as a general Fault indicator.
    From your description of the fault, I think it is more likely to be in the logic control area rather than the high power section of the inverter, but I would still start looking from the AC mains input onwards. There may be one or more 4-terminal bridge rectifier blocks, which feed 325v DC to a bank of capacitors. This DC bus runs the power inverter. A soft-start delay circuit, perhaps with a relay, may be installed to pre-charge the capacitors at initial power-on. It's worth checking all connections in this area, especially the push-on tags on the power switch and the rectifier bridges. ** Note that dangerous high AC and DC voltages are present, even for some time after removal of power.**
    A separate small inverter board may provide low-voltage power for the logic - such as 3.3v or 5v. Check that all plugs on cables between boards are fully seated. Due to the effect where the MIG wire was just glowing, it would be an idea to check for a sensor on the output current. This may be a pick-up coil or Hall effect device, or a current measuring shunt on an output path.
     
  3. Dan The Welder Man Member

    Messages:
    15
    Location:
    Uk, Leicestershire
    Thanks for the reply. I have double checked the connectors and they look good to me. I think going to a repair shop is the way forward.
    One potentially important point I missed before was that when this first issue arose, there was a short period of time when the issue stopped. I opened the welder to check inside and when tried the gun again, I noticed the wire fed through without a problem. I laid a weld bead down and it was as good as new. I repeated this a few times with different settings to double check and it all worked fine. It was only when I put the body back together and retested on a workpiece the problem came up again. This suggests it’s potentially not a faulty component as surely it wouldn’t have worked for a short time after the problem first came up?
    Not sure if this helps to identify what the problem may be but if anyone else has any suggestions, please let me know. I think I will book it into a repair shop later this week.
    Thanks,
     
  4. eddie49 Member

    Agreed, if a component had failed it is unlikely that the welder would have started working again. It does sound more like a contact problem.
    Could the casing be putting pressure on a cable, or flexing the PCB and opening a cracked PCB track? I'd suggest removing the case and trying to use it again without the case.
     
  5. Pigeon_Droppings2 Member

    Messages:
    2,701
    Location:
    london
    On the Kemppi the torch is permanently attached to the machine (at least mine is!) ....maybe it's had some rough treatment in the past and there is some damage in the torch/cable/machine attachment point.

    I'd start by looking at the the obvious things that may have been damaged....is there any damage to the case anywhere on the machine?

    I've got a similar machine...Kemppi but a different model...the case seems pretty robust. Got any pics (inside and outside)...we might be able to spot something in the pics.

    Does the fan still come on when the machine is on?
     
  6. Dan The Welder Man Member

    Messages:
    15
    Location:
    Uk, Leicestershire
    I have tried both with and without the case and no luck unfortunately. That’s an interesting point about a cracked PCB track. I’ll take a close look at the entire track although the PCB looks in good condition. When putting the case back on, it doesn’t seem to flex any internals - it fits smoothly.
    It’s strange that only low feed rates are are ‘allowed’ and there seems to be quite a clear cutoff (above 3m/ min) when the ticking kicks in and stops the wire feeding. I wonder if it’s not to do with the wire feed but actually the higher power associated with higher feeds as this is automatic? It’s almost like it’s not getting the power it needs so doesn’t let itself run at higher speeds. Having said that, the problem is still there on manual mode where the two can be changed independently. Even more strange that even at these low feeds the machine immediately cuts out on contact with the workpiece.

    To be honest the torch also looks it good condition as well. I checked all the connections inside and they are all tight and clean. There is no damage to the case whatsoever, definitely not damage that indicates any impact such as a drop. Like you say the case is fairly solid and fits well over the internals without any resistance. The fans comes on as soon as the power is on. This has always been the case and I presume is normal. Unfortunately the back of the main PCB is facing outwards and covers almost all of the components inside so very little can actually be seen from any photos. I’m hesitant to remove this main PCB for now as it’s the foundation for all other components/ wires/ gas hose etc.
    Thank you for your help and suggestions. I’ll have one last look over inc. the torch and PCB.
     
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