Just happen to have this problem yesterday.
My 150w power RECI tube has very odd power output.
We did test using paper; directly shooting out from the laser lens, and this is what we got:

At low power 4ma the burn mark is a huge round circle about 1/2” diameter, without mark at the center.
10-12ma is the best; small dot of 3mm diameter
As it goes higher ma, the dot disappear; no lasted power output from the tube.

Throughout the test, we could see the tube having its laser beam across the tube. But surprising at above 15ma there is laser beam across the tube, but no burn mark output at all.
As I increases the power output I can see clearly the brightness of the laser beam across the tube increases, but yet above 15ma there seems to be almost nothing after the laser tube lens.


Attached are the pictures of the burn mark.





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