THC Troubleshooting (No resistance)

When I unplug it I am unplugging it from the control box.

OK so lets do the same test but unplug it from the VIM rather than the control box, then plug it back into the vim and unplug the DIV input from the VIM and retest, then plug the DIV input back in and disconnect it from he plasma cutter and test again.

3 Tests first tests the vim to control box cable, second tests for a short in the VIM and third tests the DIV input cable.

Post those results and lets go from there.

Ok, did all three tests and all tests measured infinite resistance. So, the only time there was a reading of 1865 Ohms is when all cables are plugged in (from plasma to VIM box and VIM box to electronics box).

OK so the last test I can think of is to unplug the plasma cutter from the wall (220v) and see if that ground is interrupted. Then we need to find out if that reading is unusual? I’m hoping @langmuir-aksel might weigh in on that.

I measured mine and I have no connection (infinite resistance) with it all plugged in. So we’re on the right track. Where is your plasma cutter in relation to the table? Is it touching the frame of the table at all?

It is not touching the table but it is on a metal cart next to the table.

ok cool, the last test should tell us if it’s inside the plasma cutter

Know this is a dumb question, but how do I go about measuring this?

just unplug the plasma from the wall and then do the same test we have been doing between the USB shell and the slats.

Ok, so the only time the tests read infinite resistance is when I unplug the THC from the electronics panel. I unplugged the plasma and measured the resistance with the THC cable plugged in completely and it was reading below 10000 Ohms. Then I unplugged the THC cable from the electronics box and it read Infinite resistance.

So it seems to be an issue with the Plasma cutter that is causing the low resistance value. I can tell you on my machine I went and did this test and it’s infinite resistance. I wonder if anyone else with a razorweld could do this test and see what they get? I also hope @langmuir-aksel might have some info on this.

You don’t have access to another plasma cutter by any chance?

I don’t have access to another one unfortunately. I work at a university and asked one of our electricians to come and look at it and he said the same thing- its a problem with/inside the plasma. I greatly appreciate your help @ScottNH. You have been so helpful! Ill keep you updated with what @langmuirsystems says.

Sounds good. I am looking forward to hearing how it gets solved. How old is the plasma cutter?

Brand new. Less than 6 months old but I already had to return it because the THC 2 pin socket would not ‘click’ into the plasma cutter when I first got it. I returned it and they ‘fixed’ it. I wonder if that is still part of the problem.

Sounds like it could be. I wonder if that is where the short is, in that connector. It doesn’t seem like a dead short but there is some amount of conductivity in there.

@ScottNH received a response from Langmuir (see below) but not sure it makes that much sense to me so thought I would share since you have walked through this process with me.

“It is quite reasonable to assume the THC computer chip failed. A wire could have opened up. Also, the arc voltage signal does go through the Motion Control Board on its way to THC. So a chance exists MCB could be involved. At this point I would look to replace THC chip. Your thoughts?”

Could be but when you disconnect the plasma cutter it stops measuring resistance. That’s where they lose me. You could pull the THC module out and see if you get the same test results. At the end of the day they see a lot of this stuff so I would defer to them.

So I ordered and installed a new Motion Control Board and the THC chip and it still is not working. I have attached the new MCB installed and the old MCB (which does look like it was ‘fried’ where the THC chip connects).

I also ran the THC voltage test, and it was still measuring 0. Anyone know what next steps to take or what could possibly be the issue?

Did you ever test to see if you’re getting voltage from the divided voltage port on the plasma cutter?

That would be a good place to start. If there is no voltage coming from that port, while the torch is firing, the problem is definitely in the plasma cutter.

I measured 2.3V from the divided voltage port on the plasma cutter.