Live Voltage Interference at idle

Iv had this issue on my XR before and it turned out the one of the limit switches were back feeding and creating sporadic live voltage when nothing was cutting. Disconnected those and it reads zero resting.

Now my Pro is doing it (no limit switches). I spent an hour on the phone with tech. I even hooked up my other Pro control box and it will still show live voltage at 19-32v (it changes). Odd thing is. If I unhook the plasma ground it goes to zero (plasma not even turned on, no power). If I unhook the IHS cable, it will go to zero. I notice while cutting, soon as the torch stands off on metal, reading goes to zero. After it lifts up, I get voltage when its not cutting.

I have always ran all my machines with 0 on live voltage when its not cutting. I have ran this specific machine, programs, HYP XP45 many times, no issues. But now this crept up. I aim to unplug each motor and see if one of those aren’t back feeding. I thought for sure switching the control box out would prove something.

While on phone with tech, right bf we got off the line, I hooked IHS cable back in and got a zero reading. Cut the next day for a couple hours and all the sudden I get live voltage on idle.

If I unhook the ground clamp on plasma, no matter if its on or off, that will get me to zero. IHS cable unhooked gets me to zero. I even tried a brand new VIM box, not difference.

I also noticed today, when I powered off the control box, my FC was still lit up, I could hit buttons, I reset my pierces. ON all the FC stuff it always would turn grey and be inactive once the control box was powered off. I found that very odd. Im running latest firmware and FC.

When live voltage is too high it starts acting up things. I can get by with this, but something is def off.

Any help would be appreciated. thanks

All of your symptoms and tests seems to point to the IHS switch being the conduit for the voltage. Something is feeding that voltage into the table frame. It would seem that the source is the plasma cutter positive lead(work clamp). Have you tried leaving the clamp attached, but unplugging the plasma cutter?

I have had live voltage feeding back through my Pro table in the past and I could watch the reading change by moving the work clamp cable away from the control box. This was with the plasma on, though. I never tried it without the plasma cutter turned on.

Many people have experienced live voltage feeding back through the IHS switch contacts when they get covered in metal dust. The voltage is generally not as high as you are seeing, though.

Thanks for the response. I have not tried unplugging plasma from wall and leaving work clamp on. I used air to blow off all the Z axis stuff, but perhaps there is an issue in there. I will try unplugging each motor as well to see if one of them aren’t causing it.

Well, I may have found the issue. I’ll know more today when I cut. The insulator plate in the back of the z axis where the IHS wire connects to, I wiped it off (oil and metal dust I assume) created enough of a contact. So when I cleaned it off I got a zero volt reading. I initially was just blowing that whole unit out with air. I changed the control box and IHS cord from my other table and was getting live voltage. I unplugged plasma from wall, but left ground cable on Id still get voltage. So I just had a feeling it was something in the Z axis.

So after all the hoops it was just the simplest thing.


That is often the case. But it takes the effort, like you did, to find it.

Yeah to be honest, I called XR support just bc I needed to talk to someone. Iv talked to cameron alot. But it goes straight to VM. All PRO tech is via email (that sux). I did talk to a guy for an hour (he called me) and honestly some of it was helpful but it didn’t solve the issue one bit. I use the XR and PRO back to back cutting. I make my living by cutting and fabbing. I outsource some cutting. But moral of it, Im leaning away from plasma and just seems like LM isn’t operating quite the same lately. I can’t afford any downtime. Thats why Iv always had multiple machines and have backups. I felt somewhat helpless with this one. It was ongoing for days with no resolve. But thankfully its good now.

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I’m sorry to hear that. I have the luxury of having this solely as a hobby.

But jobs and obligations change things into much more stressful matters. I do not operate well under pressure of time. I have done 4 kitchens worth of cabinets. I have been approached be many builders to do cabinets for their homes thru the years. I turned all of them down for that reason that it would change my enjoyment of the creation to a “job” and a great deal of stress with added timelines. I had enough of that with my full time job.

Good luck to you. I hope this is just a hiccup in your job and plasma issues.


I love what I do, very blessed. But lots at stake, lots of pressure etc. Iv had about every issue with LM possible honestly. I have 2 crossfires, 2 pros, 1 xr and the mr. ALL of which has given me fits. The XR they hard to rewrite some firmware bc of me! Plasma is good for starters and can be decent on a professional level but it has alot of limitations and draw backs. Knowing when to say no to work is a good thing. Not all jobs are worth taking on.

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