The first step is determining what your problem is and then zeroing in on that area. Some printers have display panels which can relay information about the printer’s status, others do not. They might have a series of LEDs or lights that blink or flash. In that case you will need to have some reference material for the printer to determine what the blinking lights are indicating. Some more advanced printers will have the capability of retaining the failure codes,or error log which will keep track of previous errors that have occurred. This will provide a lot of useful information on the history of the printer. This log can be printed if the printer is operational or even viewed via the printers display panel.
If the printer is jamming you should try to isolate the jamming issue to an area of the printer. Is it at the pickup/feed area, transport area (under the drum), fuser or the exit area? Keep it simple, if it is at the pickup area try cleaning the roller(s). If the jamming is less frequent now, maybe new roller(s) will correct the problem. Try using a different input (tray) and see if the problem is tray specific. If the jam is due to multiple sheets being pulled in you should suspect the separation roller and pad, these are responsible for preventing more than one sheet at a time from entering the printer. Paper getting stuck in the fuser is most likely the fuser is at fault, sticky paper sensor, heating film (sleeve) slipping or just plain worn out.
Many printers have a recommended maintenance interval. 100k, 200k or even 300k pages between replacement of the pickup, feed, separation roller, transfer roller and fuser assy. The printer keeps track of the cycles or printed pages that have passed through and will alert you when it is getting close to the time for replacement and then when it’s time to be changed.
Print quality problems can be caused by a few different things. The toner cartridge, fuser, transfer roller, or even faulty components of the printer such as the laser scanner or power supply. A visual inspection of the toner cartridge and fuser can be an easy thing to check. Removal is usually fairly simple,check for scratches or marks on the on the drum.These marks will correspond to a repeating defect in the vertical direction on the page. The drum surface should be clean when it is removed from the printer after a print cycle. If not, there is problem with the cleaning mechanism within the cartridge. It will need to be replaced. Check the the fixing film or hot roller for marks, scratches or tears. Again there would be corresponding marks in the vertical direction down the page. Either should be replaced if they fail visual inspection. A simple yet effective test is start a print test from the menu and stop it half way through the printer before it gets to the fuser. This will show any defects in the print process before it gets to the fuser, helping you to determine which one is the cause of your print defect.
Tray 1 or the multipurpose tray works best as you can see the media going into the printer. If other media besides plain paper is being used you should ensure that the proper settings are being used or smudging,smearing and streaking will occur as the printer is unable to properly transfer and fuse the toner to the label,envelope or transparency. Other causes such as wavy lines from a faulty laser scanner. Black or blank pages from a defective power supply, DC controller, laser scanner assembly or even a formatter. Removal of the formatter and running of an engine test,usually a line test pattern will help you to eliminate the formatter as a possible cause of failure. Most HP laser printers (Canon engines) have a built in test feature, a microswitch on the DC controller or ECU (engine control unit) which will print standalone without the formatter installed. Usually a small access hole in the cover where the DC controller or ECU reside will give you access to this test. A small, thin non-conductive (plastic, wood) tool is best to use for this test.Inserted into the hole in the cover will activate the microswitch, and print a single page test. Holding the switch down on some printers will generate a continuous test.
Do the easy things first, and by the process of elimination you will find your solution.