I have sh-g350 50w laser machine. It was working fine but today when I press pulse button it will not fire at all, unless I set max power to 20% or above! It cuts and engraves even at 10% power otherwise. Makes no sense to me... I tried pulsing at 10% and 15%, nothing, at 20% pulsing burnes with high power (makes a hole) so im sure tube is good...