Laser stops fireing when above 55% power

[seeigecannon]

Ok, so I have a PSU and DSP from LO, but the laser tube came with the laser. Both the tube and the PSU are 60W. When I set the laser to 55% and hold the fire laser button the tube runs as long as I hold that button down (with a draw of 9mA according to my DMM). However, when I set it to 56% the laser will only fire for a second, then it will stop lasing completely. The interesting thing is that the power draw will jump to 17mA with no power actually coming out of the tube. If I let go of the button and press it again right away the laser will not fire (but still draws 17mA). If I let the button go and wait 10 seconds or so then hold the laser button again the laser will fire properly for a couple more seconds. Any thoughts what might be going on?

More info: I am running a couple of pots to set a trickle and max current as posted here viewtopic.php?f=8&t=2522. (Hopefully I will have the digital version of this done at some point.) I did not think that was what was causing the problem as it used to work just fine, but I removed it anyway and then it just started to fail when the laser was set to ~30%. There is good water flow and the water temperature is at 23C (at the upper end of what is recommended). I have also tried playing around with the PWM frequency, but it acts the same no matter where I set it (between 5k and 50kHz). There is a flow switch on the laser, so it would have never been run without water.

[seeigecannon]

More info: I hooked up my scope to the control lines and I found that the PWM signal going to the LPSU was very noisy (as well as everything else), so I threw a bunch of extra capacitors in it. The voltage noise floor went from about 3V to less than .5V. This did not help anything, but at least the signals are much cleaner.

I also arranged my phone camera in such a way that it acted like a mirror to let me look at the laser tube as it is firing. When the laser is actually lasing and drawing 9mA the tube glows at a certain intensity. When I bump up the power by a couple percentage points the tube draws 19mA and instantly glows very bright. Putting a piece of paper in front of the tube when it is doing this is not able to burn the paper.

Is there any way for me to verify the laser tube functionality before putting in for a new one?

[Tech_Marco]

It seems that the tube is gone if there is purple light grow up inside of the tube but can't burn anything.

Marco

[seeigecannon]

Putting this here for others in the future:

The laser tube was indeed blown. It also got worse over the next couple of days.