There's nothing wrong with the printer, they just draw a lot of current. I have a Xerox Phaser 6100 color laser that's rated at 10 A. The flickering you experience is probably caused by the fuser lamp turning on, to heat up the fuser rollers. It takes a lot of heat to melt the toner into the grain of the paper. Of course, there is also HVDC in there which makes the toner stick to the paper in the desired pattern before it goes through the fuser.
