I have a Xerox 3117 laser printer which I bought secondhand but has always printed too faint. I saw a YouTube video about cleaning some internal mirrors. I tried that and it made a slight improvement but still not satisfactory. I just watched another video about refilling the toner cartridge. Apparently this is possible on the 3117 because there is no internal electronics monitoring the toner usage. I don't get a low toner light when printing but it is worth a try to see if it helps. I have an old toner cartridge from a previous Samsung printer so I dismantled that to see if it contained spare powder. It did contain some powder but there was also what looked like polyurethane foam that has biodegraded and is falling to pieces. I won't attempt to use this old powder but would welcome any advice on maintaining these printers.