A black line on one edge is usually caused by either a leaking cartridge or a failed fuser film. Remove the toner cartridge and look inside the printer can you see a lot of toner inside the pritner, if yes then a seal has failed on the cartridge and a replacement should resolve the problem. No toner? Look at the bottom of the cartridge at the green/blue drum. Does it have a mark that corresponds to the mark on the paper, if yes, cartridge is bad. If you have neither of these conditions then the next likely issue is a failed fuser film. Can you post a sample of what you are seeing?
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