Hi again, thank you for replies.
After too many trial and error I found the problem.
Mirror on tube out (I think it's a mirror-bottom right picture, laser out nozzle) is smoked.
This part is inside of tube and can not be replaced. Then I change tube, now laser point is nearly perfect circle, all cuts straight and cuts better (faster than old tube).
With 60W I can cut 12mm plywood but not all kind playwood. I'm in model plane business and I work with soft woods, mostly balsa and other woods using for modelling.
But it's sad that how can be 280 hour old tube can be junk? I never heard shelf life or something similar for laser tubes. The replacement tube is 4 year old also, I buy it with machine because at that time was very difficult to find a new tube. Two tubes, same age (So can not be shelf life) one of not dead but blind!
factory fault maybe?
Is there a way change internal mirror? (If it is a mirror)
How can cutting tickness affect tube? There is no physical contact between tube and cutting metarial. This interesting detail, I wondered.
Can my hardware drive 100W with out any other changes? Tube V and mA must be different?