Had my plasma table for over a year and my THC would work for a while then quit then work for a while then quit. To be honest, I always kind of marked it up to it being on the low end of the cost spectrum. I was always more interested in making parts than troubleshooting the system for Langmuir so it was never high on the priority to fix. Finally started causing a few issues on pattern cutting, so I decided to take a day and see what I could figure out. If anyone has used the troubleshooting flow diagram step by step you realize why it took an entire day. I got to the end and still had no real answer because my test voltage was still in the 0 to 30 volt range and the VIM box input and output were fine. I have more noise blockers on cables and USB ports than anyone should ever use and still no good. My setup is a Notebook and was running it on battery. I had everything that took 110 on a separate circuit like all the posts say to do. My electronics were on the ground on a rubber mat. I was ready to say I knew I was wasting a day and decided to try one more thing…
I was using an external monitor on my laptop because I wanted a bigger screen to see from a couple of feet away. Because it was in my shop let’s say it was an older model that was kicked out of the office years ago. I disconnected it and unplugged it from the system and all of a sudden I was getting 130 volts to 150 volts… Started looking at the monitor and was an old type that the 110v plug was plugged straight into the case of the monitor which meant the transformer was in the monitor… Started making more sense. I got a new monitor that has an AC to DC converter in the cord and my readings only fell about 10 volts.
Please before everyone starts pointing out why I should have known this before… I am not an electrical engineer or an instrument tech nor do I want to be one.
The only reason I wrote this is because in all the posts I read I never saw one that said, “If you have an old monitor with a transformer built-in unplug it because it might be the problem.”
Hope it helps someone else.