What causes a torch to go live?

[Furry Freak]

Guys, this is a rather general question to a specific problem that I had today. My torch went live - without the trigger AND when I switched the set off on the box. Huh? Now without getting into my particular set, can anyone tell me how this could happen in general terms. I shall contact the supplier tomorrow, but am rather curious. I stripped everything down, cleaned it and reassembled. It's a Euro torch, incidentally. I don't pretend to understand how a MIG works, xcept to say that I presume that when I pull the trigger, the wire becomes live, the gas valve opens and off you go. I don't know if the current gets fed in at the torch or up the wire from the feed roller end.

But anyway, with the set off, how is power getting to the tip? That has to be a major short somewhere in the mains end doesn't it?

Any thoughts

FF

 

[madkayaker]

sounds like the contactor for the tranformer has welded on

 

[rtbcomp]

Power gets to the tip up a thick conductor in the torch lead.

With the torch live under the fault descriptions you describe, does the wire feed?

Or do you just get a brief spark and then it goes dead? If this is so it's most likely to be capacitors in the welder discharging, which is perfectly normal.

 

[weldingscotty803]

you been giving it some hammer FF?

 

[Hitch]

Id go with a sticky contactor as a first try. The spark after you switched off is probably the capacitors.

Power is transfered along the torch through a copper cable and then to the wire by the contact tip.

 

[Furry Freak]

Thanks guys, no the torch doesn't feed. Like I say, it does this with the set switched off so the motor doesn't run. It sparks several times. I tried it at least 3 or 4 times in between fiddling and it sparked each time.

In terms of it being normal, I don't think that it is. It's never done before this as you can touch the electrode to the workpiece (to line yourself up for example in a tricky corner) and it's never sparked before.

it seems to be welding perfectly normally. Just when you touch anything in between runs that it sparks all over the place. It's doing it less frequently now. Will see what the Sparks at the weldshop says tomorrow.

Thanks for the explanation fellas. It's always handy to have a bit of background knowledge so that you don't sound like a total muppet when asking the experts in the shop!

FF

 

[Hitch]

Weve had it on the Migatronics at work too, PCB faults.

 

[madkayaker]

the feed motor and gas are probily controled by different control circuitry the the main contactor and the main contactor staying in would not activate the control for the feed motor. try unpluging the unit and then plug back in and see if you can hear the transformer humming into life if the conctor is sticking switch solvant normal cleams them out or a little tap will also help do that at work reguly with 500A contactors

 

[Robotstar5]

if the conctor is sticking switch solvant normal cleams them out or a little tap will also help do that at work reguly with 500A contactors

It's only prolonging the inevitable! better off changing the contactor

 

[madkayaker]

sometimes not that easy! some are the old BT type that you can't get any longer and would meen rebuilding new panels for the series wound DC motors

 

[Robotstar5]

sometimes not that easy! some are the old BT type that you can't get any longer and would meen rebuilding new panels for the series wound DC motors

You wanted a bit of overtime to buy more toys for your LW?

 

[madkayaker]

got plenty of T&I to do first!

 

[michael1703]

needs a blow job!

remove the euro torch fitting and blow the contacts clean with the airline

 

[Furry Freak]

It's not old fortunately, it's only a year into a three year RTB warranty. They'll have it fixed I'm sure. Just can't be without the set at the minute, trying to get my winch bumper finished for the weekend!


FF