These machines are not always good, there is fixes to do before you plug it to your wall outlet.
Check out our articles in the electronics category to fix, upgrade or just learn more about your K40 laser cutter/engraver.

Remember: When working with high voltages, your local laws and regulations can differ on what you are allowed to do yourself and what you need to hire licensed electricians for. Never touch if you aren´t 100% sure you know what you are doing.