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Problems with a Miller Plasma Cutter


New member
May 20, 2020
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Hi all,

Can someone can help me solve a mystery with a Miller Spectrum 375 plasma cutter. It's an older unit (not one of the newer "Extreme" models). I bought it used and when I plug it in at my garage it powers up and when I pull the trigger on it, it strikes the pilot arc and then immediately cuts out and the power light flashes on/off. According to the manual, that means there are power related issues.

It's plugged into a 240V 50Amp plug. I've checked voltage at the plug and it's correct. I use the same outlet for my welder and it has no problems running off that outlet.
I've put all new miller consumables on the plasma cutter. I have also verified the air pressure. FYI - The cup (consumables) and air pressure error lights do not come on.
I've taken the plug apart and cleaned up the connections and verified it was wired correctly.

I took the plasma cutter back to the guy I bought it from and plugged it in at his shop - it works perfectly. Cuts like it should and does everything as plasma cutter should do. Take it back to my place - it strikes the arc and then cuts out and flashes the error light.

What am I missing?
Last edited:
Is the switch on the back switched to the 220v position?
Have you taken the gun apart and cleaned the contacts in the trigger? just a thought.
If it works right on other peoples power, it still sounds like a power issue in your shop, but if it tests out ok , I dont know what could cause it.
maybe an electrician is in order.
Mine did that, I replaced the swirl ring, electrode and tip and it worked fine after that. Not sure what caused that but there is some interlock that keeps it from firing when the tip is apart.
Check the outlet.

Make sure it has good connections.

Actually maybe just change it. It is likely a crummy source connection.
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