Purge valve

[Nelson]

I am bringing my Astro Turbo 130 mig welder (same as Cebora and Snap-On) back to life by converting to a Euro torch. I want to add a gas purge button but can't find a constant voltage source. Can anyone tell me where I can tap into a power source that will be hot when the trigger is not pressed, and won't change voltage when the wire feed speed changes?
Rick

 

[roofman]

I am bringing my Astro Turbo 130 mig welder (same as Cebora and Snap-On) back to life by converting to a Euro torch. I want to add a gas purge button but can't find a constant voltage source. Can anyone tell me where I can tap into a power source that will be hot when the trigger is not pressed, and won't change voltage when the wire feed speed changes?
Rick

power in block before all the trickery thats were i always add an extra cooling fan feed. Oh and welcome to the forum

 

[rikrobson]

Have a look at my thread on the subject. I put one on mine. It was a on off momentary switch. You could turn it off when changing wire or purge the gas

 

[rtbcomp]

Or you could put a switch in series with the motor so it doesn't run when you pull the trigger and purge using the trigger.

What voltage is the valve?

If you do fit a separate switch use a change-over type so you don't feed current back into the motor circuit when you purge.

 

[Nelson]

I have a 120v AC solenoid valve installed. I'm in the US where we have 110v mains. I have other solenoid valves, so swapping it would not be a problem. I was thinking of adding a 120v NO momentary switch to activate the valve without pulling the torch trigger, but that may not work. I'm not much of an electrician. I didn't think of the power flowing back to the other components. Should I add some kind of diode to prevent that, or find a different switch?
I'll try to post photos to show where I am with the project. Please excuse the messy background.

Rick

 

[rtbcomp]

A diode won't block AC (well half of it anyway).

A SPDT (changeover switch) would be the best bet.

 

[Nelson]

I forgot to mention...rikrobson this project is the result of your post. When my original torch valve wouldn't stop the gas flow and the wire wouldn't feed smoothly, I started looking for replacement options. Your post inspired me to try this conversion. Thanks!
My lack of electrical experience is delaying the project. Your post and photos got me this far. I couldn't work out the purge wiring, though, and I can't make any sense out of that (or any) electrical diagram.

 

[Nelson]

Thank you, rtbcomp! You may have saved the project. I'll try to find the proper switch on Monday.

 

[Nelson]

If I put a switch in to turn off wire feed motor, could I also divert the power to a plug for a spool gun? If I did that, could I weld aluminum with a spool gun with a euro plug? I know I would have to use pure argon gas.
Sorry this is getting off track. I was just thinking of options.

 

[Russs]

Hello Nelson,
I just found the site and realize your post is more than four years old so I might have moved on with your Powemig 130. I just bought an NOS unit however it does not have the Owners manual. I want to set mine up to Fluxcore weld however am not sure where to position the ground and torch wires for proper setup, do you have the instruction manual by any chance? If not maybe you can provide mw with a pic of your unit setup for Fluxcore welding. After you are finished laughing let me know if you can help. Tkas.

 

[eddie49]

Reversing the torch and the work return lead ( "ground" or Earth clamp ) polarity is quite straightforward.
Originally, the heavy cable from the torch/wirefeed assembly goes to the rectifier positive output, and the work return cable goes to the metal plate that parallels-up the output contacts on the Contactor ( heavy duty relay ). This is the negative side of the welder, and comes from the rectifier negative output, then the inductor ( choke coil ) and then the paralleled Contactor input contacts.
To reverse polarity, move the bolted connection of the torch cable from the rectifier positive to the contactor output, and move the work return cable from the contactor output to the rectifier positive.
This change has swapped polarity, but there may now be an issue with the single thin wire for the torch trigger switch. Rather than a microswitch, the torch switch is just a flat spring blade that presses onto the brass block in the torch head. Originally that would send a positive voltage to the control board. However, after the polarity swap the torch head is now negative, so the trigger will not work. One way to solve this is to add a second wire to the torch, joining to either a real microswitch or an insulated contact which the flat blade will press against.