I have an inexpensive, 40W CO2 laser which has been working great for my simple uses. I had been using it without problem last week. Then, the next day, I went to turn it on and nothing... After some investigating, I determined that it was a power supply failure, so I ordered a replacement, which, after installed works fine. However, I started noticing that I was not getting the normal power output as I was before and, when cutting at full power, the beam looks "grainy" and erratic. I also noticed an electrical "buzzing" sound that was not there before. So, I ran the cutter with the tube exposed so I could see what was going on; this is what I saw (see YouTube video): https://youtu.be/uCVXQ97J7dI

Before running this test, I replaced all my cooling water with new, distilled water and ensure that there were no air bubbles in the tube's cooling chamber.

I fear the worst, that my tube has somehow failed (even though I have not used it that much), but would like some other opinions.