Hello, I have an extra tube that came with my machine that was never used. I recently started using it and it's only been a month. Last night it suddenly lost most of its power mid-cut. After checking focus I went home then came back in this morning. I was excited to find the laser cutting at full power again but it only lasted about 30 minutes before it lost almost all power and was barely cutting. I checked the lens for damage then checked the focus. I noticed that the laser was firing a circle with an empty middle. I then started to trouble shoot starting at the tube itself. I fired the tube onto a piece of wood and got the same thing, low power and a circle with an empty middle. I tested the power supply next and used the resister that came with the laser. The power was firing at full power so I've determined that the supply was fine. I also learned that there's a lens in the tube itself and I did a visual check looking in the end of the tube and all looked fine. I also did a visual check of the tube which looks fine. That's about as far as I've gotten but at this point I fear it's the tube that's gone or if not I don't know what else to troubleshoot. Any ideas? I've attached a photo of what the laser looks like when it hits the piece. 150W Chinese tube water chilled