No arc from 'new' Power Craft welder

  1. JonB1985 Member

    Messages:
    12
    Location:
    Bristol UK
    Hi all, I'm new to the forum, I have a Power Craft combination gas / no gas MIG welder 30-135A.... I bought it possibly 10 years ago but embarrassingly haven't attempted to use it until now (life got in the way of my welding plans, but now I finally have a worthy project!). It's been stored dry and boxed up all this time.

    But there appears to be a problem with it. It turns on, the fan spins up, and when I press the trigger the wire feeds correctly... But there's no arc. I've even tried aiming directly at the earth clamp, but nothing. The 'overload' light does not illuminate, so it's not that.

    I've initially been attempting to use the 0.9mm flux cored wire that it was supplied with (with reversed polarity according to the instructions). It also came with gas welding wire and equipment too which I haven't yet tried.

    Could this be a problem with set up or does it sound like a fault? Can anybody advise on how I can determine what the problem might be? Attached is a photo of the welder and the wiring diagram.

    Thanks in advance!
     
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  2. gaz1

    gaz1 Forum Supporter

    Messages:
    8,439
    Location:
    westyorkshire
    try it with normal polarity and make sure those connectors are in correctly

    if no arc then could be dodgy from day one

    it works by the diodes from transformer the torch is just the trigger for the wire to feed by the motor so if motor feeds and no arc your looking more at the diodes been at fault sometimes its not worth trying to repair it

    power craft is not a good make you would have been better with a sip at least it works but that isnt the best as it used to be next up is the clarke get more repairs with that done than most machines out there and still going strong for years its done
     
  3. JonB1985 Member

    Messages:
    12
    Location:
    Bristol UK
    Thanks, yes I've tried both normal and reverse polarity and the connectors look good.

    So if it looks like the diodes are at fault, is it possible to find the source of the problem and repair? I see what you mean about not a being a good make, if it can't arc on first use!
    However I can't afford to replace it, so if there is a possible fix, I'd like to explore that. Any thoughts, or is it genuinely ready for the tip?

    Thanks
     
  4. Rig Pig

    Rig Pig Member

    Messages:
    3,492
    Location:
    Narrwich! U.K.
    Before you condemn anything disconnect the machine, remove the covers and check all the wires are connected. If you can't hear a clunk when you pull the trigger then look around the relay that suppliers the transformer.
     
  5. Rototype New Member

    Messages:
    4
    Location:
    UK
    Hi Jon,

    While you're looking around the big relay on the circuit board have a look at the fuses there (I seem to remember there's 2), it's always possible that one's popped or not inserted correctly, also check the other connections on the board. There's also a couple of capacitors on the board near the big relay that might have gone short circuit, these will be aluminium tubes with plastic sleeving, look to see if any of them look as if they've leaked. If you feel comfortable with a multimeter in there with the power on, you can check the (AC) voltage into the diodes and the (DC) voltage out of them. If there's no AC voltage then it's either the transformer or the relay or some of the driver components for the relay. If you have AC but not DC, or the DC voltage is noticeably lower than the AC voltage then it's the diodes that have gone. If you have DC voltage and it's still not giving anything on the output it could be the 'choke' (big transformer looking bit at the front with 2 fat 'wires' coming out of it (1 to the rectifier negative and the other to the negative terminal). The way to test the choke (this can be done with the power off) is to set the meter to the Ohms or conductivity setting and put the probes across the terminals of the choke. You should see a very low resistance that could easily be read as a short (it's meant to be). If you get no conductivity through the choke then that's probably your culprit.

    Sadly these are well out of production, and the company that made them (Wolf) went bust in 2009 so you'll be very hard pressed to get any spares for it apart from the generic components.

    The diodes are referred to as 'capsule' diodes and are pressed into the aluminium plates, these could be pressed out and new ones pressed in but it's probably easier (and cheaper) to find a working rectifier (diode) unit from another welder and fit that (most are similar - just make sure you get one rated the same or higher current).

    Another option is it could be one of the wires on the switch unit come loose - check these carefully and tighten any loose screws.

    Hope this helps
    Tim
     
  6. JonB1985 Member

    Messages:
    12
    Location:
    Bristol UK
    Thanks for the great help guys - Tim especially for talking me through it- I wouldn't have had a clue without that.
    I've taken the sides off - photo attached, Tim you were right there are 2 fuses but both are fine. The relay clicks when I press the trigger and all the capacitors and connectors appear (visually) OK. I used my multimeter and the choke has a very low resistance indeed - about 0.8 ohms.

    With the welder powered up and switched to the lowest power setting, and trigger pressed, the voltage into the rectifier* is 23.8V AC, and the voltage out is 20V DC.
    The voltage across the main terminals to the weld nozzle is about 10.8V DC - should it be higher?. This drops to zero when I touch the nozzle onto the earth clamp (which I guess would make sense as I've short circuited)...but no arc.

    *I was little confused that the circuit diagram (attached to my first post) appears to show 2 rectifiers where I think I only see 1. Maybe I'm missing something obvious. Anyway I was measuring the terminals on each of the two large flat plates (top-middle of the attached pic) for the DC output, and the inputs to the diodes (that meet in between the flat plates) for the AC input measurement. Was I doing the right thing?

    Do my voltage/resistance measurements give a clue as to where the problem lies? I'm not sure what values would be expected.

    Thanks a lot!

    Jon
     
    • welder.jpg
  7. Sean Another 602 fan

    Messages:
    1,093
    Edinburgh
    so its been sat for 10 yrs, have you tried flicking all the switches and rattling the relays with the power on as they may have become corroded/stuck.
     
  8. JonB1985 Member

    Messages:
    12
    Location:
    Bristol UK
    Yes tried that, and it's been stored in the house (not a garage or shed)... so there doesn't appear to be any corrosion anywhere.

    What I can't understand is, since there seems to be voltage at the terminals, why it doesn't produce an arc!
     
    Last edited: Aug 24, 2018
  9. tinker jim Member

    Messages:
    207
    Location:
    birminham
    Check the connections after the rectifier the points were you can change polarity as a loose connection on these will cause a high resistance in a low voltage circuit will equal no arc common issue on welders stored for long periods.
     
  10. David Nightingale New Member

    Messages:
    13
    Location:
    Chester
    Hi, I have the same welder. Has given me fantastic service, until recently. I had exactly the same problem. Got out the multi meter, even though there was voltage at the torch, there was no current to weld. I was convinced it was the rectifier, I was 2 seconds away from "Buy It Now" on my fav auction site for a replacement, then I thought I would just check again. I removed the short link cable from the +ve rectifier plate to the stud that goes through to the wire feed rollers side and it fell apart in my hands. The heat shrink was holding the badly corroded cable together! This is a very poorly made part on this otherwise great welder. It is badly crimped / soldered cable that takes all the current a "weak link". I have upgraded mine with 25mm cable and correctly crimped terminals. It welds now better than before.
     
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  11. David Nightingale New Member

    Messages:
    13
    Location:
    Chester
    Just highlighted it on your picture. welder1.jpg
     
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  12. JonB1985 Member

    Messages:
    12
    Location:
    Bristol UK
    Top marks David! My cable is terribly corroded too and likewise fell apart in my hands. Photo attached.
    I haven't yet replaced but fingers crossed this must be the cause of my problems and easily fixed. Many thanks indeed. I'll report back when I've replaced.

    On that note, any recommendations on where to buy a replacement cable and the end terminals?

    Thanks again,
    Jon
     
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  13. tinker jim Member

    Messages:
    207
    Location:
    birminham
    I have some thick cables similar to that I salvaged from a fork lift I'll pop a photo up tomorrow if it' any good to you ill pop it in the post....
     
  14. Cobbler

    Cobbler Codger bodger

    Messages:
    4,358
    Location:
    Gloucestershire UK
    Any welding suppliers will have terminals of various sizes, I would think. Motor factors are the other source, if you get desperate flatten a bit of copper tube out & make one & solder it on.
     
  15. David Nightingale New Member

    Messages:
    13
    Location:
    Chester
    Hi Jon,

    Glad you managed to find the problem. It had me stumped for a bit too.

    I bought the parts off eBay, I already had the crimping tool. You can get the lugs from toolstation very good price. Car battery cable can be the right size if you are getting desperate, but I would go bigger if I was you.

    The original is 16mm2, I went to 25mm2 just to be on the safe side as I occasional weld at full power. The holes in the lugs are 8mm. I have got a small industrial unit and I have mine connected to a dedicated 16 amp supply.
     
  16. gaz1

    gaz1 Forum Supporter

    Messages:
    8,439
    Location:
    westyorkshire
    welcome to the forums

    by the way david also as someone on here found out

    thankyou for the info provided by you on the above machine
     
  17. JonB1985 Member

    Messages:
    12
    Location:
    Bristol UK
    Thanks all and Jim for the kind offer, my cable needs to be 16mm^2 or bigger, about 17cm+ long and with 8mm-10mm holes in the ends. I guess it's a long shot but if yours happens be similar then I would gladly take up your very kind offer. If not, I have found somewhere on ebay to buy the parts.
    Jon
     
  18. tinker jim Member

    Messages:
    207
    Location:
    birminham
    Is this any good 25mm squared 27cm long so bit longer than you need 8mm holes off a fork lift and the longer cables I made up for a better earth on my mig 20180828_160122.jpg
     
    David Nightingale likes this.
  19. David Nightingale New Member

    Messages:
    13
    Location:
    Chester
    That should be perfect as there is enough room to snake the cable behind the rectifier. As the whole plate is +ve you can mount it on another hole, but be careful to keep the small cable also mounted to the +ve plate or the welder will stop functioning.

    Dave
     
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  20. JonB1985 Member

    Messages:
    12
    Location:
    Bristol UK
    Jim that would be perfect, I can loop round the extra length, many thanks, I'll pm you.
     
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