Bad Laser Tube?

[Flex101]

I need HELP!
I believe I have a laser tube problem with my newly purchased laser tube. The new tube only has approx. 5 hours actual laser time and it was working fine a few days ago. Yesterday, I started noticing the lack of laser power with known successful program settings in LightBurn. I just replaced my original K40 laser tube about 1 week ago for the same exact symptoms. My best guess is something is wreaking havoc on my laser tubes. Today I opened the back of my K40 and noticed small air bubbles along the length of the tube. I attached photos of what I saw in the tube and the mirror alignment results I did right after noticing the lack of power. The bubble may be the root cause, but I'm new to this and I'm not really sure at all. If I have to spend another $235 for another laser tube, then I definitely need to research as many possibilities as possible, because the cost of two tubes will be more than a brand new K40 unit. I really need help figuring this out before it cost me a small fortune.
Here is a list of things that may aid in an opinion consideration:
• I engraved a Tiger photo that took 184 mins. straight and the water temp was never above 23c
• I normally hang my water outlet hose above the water supply bucket, so I can hear the water flowing back in the bucket during operation (audible indicator).
• The water pump circulation appears to be good and I see a solid stream returning with no visual air bubbles in the tubing.
• I never checked for air bubbles in my old laser tube, so I'm not sure if the heat from unknown bubbles may have caused the cooling tip to come off, thus causing the tube failure.
• I rotated the newly installed tube a day ago because I saw a larger bubble at the outlet side of the tube when I was aligning the mirrors. Once I rotated the tube, it was free of all bubble including the small ones.
• I’ve cleaned all mirrors and lenses and I’m still experiencing low power.
• Example of power loss: Before I could cut 3mm acrylic in one pass at 0.10 in./s, 40% max power and 75% power scale. Now it takes 6-7 passes at 0.05 in/s, 40% max power and 100% power scale.

My setup is a K40 Laser with Mini Gerbil 1.1 Controller and Lightburn 0.9.04

Thanks in advance.

[mrsunnylam]

the bubbles are not from the tube. it is from your water pump, make sure it has good pressure like 10L/min . a good way to get the bubbles out is to squeeze the silicone tubing a few times while it is running, remember bubbles in a tube will create hot spots and shorten the life if the tube.

From the pictures, are you calling mirror1, the mirror on the head closest to the lens?
or is mirror 1 closest to the laser tube?

to me it looks like a beam alignment issue, you can see how Marco does it
viewtopic.php?f=16&t=2835

the only reason i think it might be that is because your image shows the beam is not center.

[Flex101]

I truly hope my problem is just a beam alignment.

Also, Mirror #1 is the closest mirror to the output side of the laser tube.

I will try Marco's method of aligning the mirrors (beam) and see where that takes me.

Thank you very much for your opinion and suggestions.