Sparks are a flying!

[Farmerpalmer]

Hi, I wonder if I could pick your collective brains again?

A new problem has occurred with my old Butters. When the torch trigger is pulled when welding, the welding wire glows red hot in the machine and sparks fly as the wire holding reel makes contact with the body of the welder. The wire eventually melts. When the trigger is pulled when not welding everything is fine. Is there a short in the torch or the machine? I've had a quick look and can't see anything obvious. I've cleaned the shroud and tip on the gun and checked for loose wires.

There seems to be continuity between the earth terminal on the torch connector block and the wire feed-in on the back of the block. Is this normal? There are two live pins on the connector. These show continuity when the trigger is pulled. I assume this is normal.

Help!

Many thanks!!!

 

[Pete.]

Sounds like the torch conductor is open circuit.

 

[Jim Davey]

Or the wire is shorting to the frame of the welder. Is it on a metal basket?

 

[Farmerpalmer]

Thanks guys.

Yes, the wire is on a metal reel, but miles of wire has been used like that. Either I have been lucky up to now, or something has changed.

How do I check for an open circuit on the torch conductor?

 

[mike 109444]

""
Hi, I wonder if I could pick your collective brains again?

A new problem has occurred with my old Butters. When the torch trigger is pulled when welding, the welding wire glows red hot in the machine and sparks fly as the wire holding reel makes contact with the body of the welder. The wire eventually melts. When the trigger is pulled when not welding everything is fine. Is there a short in the torch or the machine? I've had a quick look and can't see anything obvious. I've cleaned the shroud and tip on the gun and checked for loose wires.

There seems to be continuity between the earth terminal on the torch connector block and the wire feed-in on the back of the block. Is this normal? There are two live pins on the connector. These show continuity when the trigger is pulled. I assume this is normal.

Help!

Many thanks!!! ""

What earth terminal on connector ?? The torch does not have a earth terminal ! The power traveling up the torch is returned (circuit completed) by the weld wire through the work piece and back through the work ground clamp.
The block (brass wire feed tube) on rear of socket is the connection point for the weld power coming from the diode pack into the torch. See pic for the thick cable caring the weld power.
The two pins on the connector are the trigger in torch connections and so should show a short when trigger is pulled. You may have some voltage on them as they connect to the pcb to operate the welder.
IF you feeder unit IS isolated from the machine chassis and the work return clamp SOCKET is also isolated then you should not get any shorting between the weld power and the chassis. Is there any form of insulation on the hub that the spool sits on or is it a metal hob/tube ? Is there a spacer missing from behind the spool that should stop the basket touchng the machine frame ? If not try adding a plastic washer maybe.

 

[Farmerpalmer]

Hi Mike, sorry for my description. Inside the torch connector block that plugs into the machine there are two sheathed cables and a much larger unsheathed copper braid that I assumed was an earth. My welder looks nothing like yours!

 

[Farmerpalmer]

This is mine!

 

[mike 109444]

Sorry about that sir, in my haste to inform I forgot to check (from your previous posts) that the torch was not a usual euro type torch.
The "thick" unsheathed cable should be the one carrying the weld power and the two thinner sheathed ones should be the trigger ones.
As the weld power is feed up the thick cable to the tip and then the weld wire, it is also able to flow back down the weld wire and to the basket of wire, through this and onto the frame ! Even though this is possible it should not short so does imply that there is a connection between the machine "frame" and the work ground clamp or it's socket (if it has a socket).
You can try metering between the work ground and the machine frame (meter set to ohms) and you may find there is a circuit.

 

[Farmerpalmer]

Thanks Mike, will do. If I find a circuit what is the likely cause/solution?

 

[mike 109444]

Don't think it's going to be easy locating cause. Because what ever is causing it must be able to carry a fair bit of current with out frying! If it was just a thin wire shorting then it would have burned out by now. If it is a component (small) resistor or capacitor then they would have vaporized !
I notice in your previous post about the duff diode that you had a plastic spool of wire loaded. Could be you need to make sure that's the type you use as I said before you could look to have an insulator between spool and frame. Make sure when you are welding that the machines frame is not touching the work as that may short.

 

[Farmerpalmer]

Just checked. With the machine off I can find no continuity between the ground and the frame. There is between ground and the diodes, but that's to be expected?

 

[Farmerpalmer]

We have used the metal reel for a while, perhaps I was just lucky, but will go back to a plastic one. The only wire to burn out in the machine is the welding wire itself. Funny it didn't do it before, but looks like lesson learnt.

 

[mike 109444]

With power to machine disconnected you may then need to manually operate the contactor ( as like pulling trigger when welding does) then meter.

 

[Farmerpalmer]

Got you. Will do, or will try it live, carefully!

 

[mike 109444]

Not a good ideal to meter for resistance/continuity in the presence of voltage !

 

[Farmerpalmer]

That shows my level of incompetence in all things electronic! Sometimes I really shouldn't be let out without supervision.

 

[Farmerpalmer]

I tested for continuity with the contactor closed and there is nothing. So looks like the metal reel is the culprit.