Is my K40 broken?


So my K40 stopped doing much. If i place paper in front of 1st mirror and test fire all I get is two outside edges of a circle about 10mm in diameter.

the amp meter show 25ma to get it to do that anything less i get nothing.

is it a dirty laser tube, a bad laser tube, bad power supply, or a bad pot? any help greatly appreciated.

Post a picture of the test paper, please.

You can also compare to pictures from other folks who have posted about tubes having shifted mode, typically to TEM01* (“donut mode”) or to TEM01 (two halves).

If your tube has shifted into a higher-order TEM than 00, it’s irreversible, and the tube is dead. A common way to reduce the lifetime of a laser tube is improper cooling. There is a lot of misinformation about cooling out there; this article may help:

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wow, THAT is very high for a K40. What’s been your typical power level on the amp meter when you’re cutting things?

typical around 8-10mA but i get nothing at that power now

The dot pattern indicates the tube is at EOL and as long as you’ve not exceeded ~18ma and never operated it above 25C it’s likely you’ve had a long and useful life from that tube.

The fact that you can get a steady 25mA from the power supply is a good indicator that it is operating fine and you just need a new tube.

Just incase you, or others, aren’t aware, the stock tubes shipped with K40 machines are of vary low quality in general and while they are claimed to be 40W lasers they can’t be operated at 40W of output without greatly degrading the tube chemistry. Most every K40 FAQ should tell you not to exceed roughly 18ma for a longer tube life. The other thing which will greatly degrade the tube life is the water temperature entering the tube. It must be below 25C with 18-20C being ideal and 25C the point at which to stop using the machine.

Good replacement 40W tubes are often tested to 50W and can operate at full 40W without excessive tube wear. So often a new tube will result in better-then-new capabilities but the installation is not like changing a light bulb. Thankfully there are lots of HowTo’s around the process.

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