HP Laserjet Printer Repair
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HP Laserjet 4 and 5
Cleaning up HP LJ 4, 4plus and 4Mplus printers (could be for LJ5 printer too)
Disassembly
- open up the cover, take out the toner cartridge and put it in a dark place
- take out the paper tray
- take off the right side skin (carefully press in two tabs)
- drop open the back cover (if you lose the spring, you can replace it with a Bic pen spring)
- Unscrew the 2 fuser screws and take out the fuser, check it for wrinkles and dirt
- Take off the top of the printer:
- unscrew the two screws on the back of the printer FIRST!
- unscrew the one screw on top
- press in the two tabs and gently lift the top up and tilt it right
- unplug the user interface cable connecting the top to the printer
- Take off the rear exit transport by pressing in the two small tabs and lifting it out
- take the top panel off the exit transport by pressing the tabs and snapping off the top
- take out the top roller and treat the thicker rollers with rubber rejuvinator
- snap the top back on and save for later reinstallation
- Check the main drive gear in the back for broken teeth (it drives the fuser)
- Open up the memory door
- Take off the small black panel on the front of the printer by pressing its tabs together
- Open up all internal panels and metal lids to check for paper remnants
- take off the left skin by pressing two tabs and lowering it to the left
- take off the right front panel with the cartridge slot in it
- be careful of the tab on the bottom of the printer as it breaks off very easily
- There are two internal tabs that need to be pressed down through a hole in the right side of the printer as well.
- If broken, take off the single sheet feed tray
- detach the upper half of the tray from the lower by carefully squeezing together the two pivot points
- take off the horizontal metal strip (with spring clip on left) (two screws)
- take off the bottom piece by carefully bending the plastic to sneak out the two pivot points from their sockets
- release the spring (on the left side) from the top plastic piece and remove it
Cleaning
- Clean off both feed rollers (large rubber wheels to pick paper)
- For the bottom feed roller, press the clip to remove it and rotate the rubber band to bring new rubber into the worn pick area
- Blow out everything with compressed air and clean all surfaces
Reinstallation
- Put rear exit transport back on. Slide pins into slots and click in two tabs
- don't forget to slide on the metal clip on the left side of the printer
- Put front single sheet feed plastic parts back on
- put horizontal metal strip with left side spring clip back on
- clip the two plastic pieces back together
- snap the small black front cover back on
- snap the front right panel (with cartridge slot) back on
- reinstall left panel. Put base tabs in and snap into place
- screw the memory door shut
- Put the top back on:
- connect the user interface panel cable
- snap the top down onto the printer
- add one screw in front-top and two screws in back
- Re-install fuser with two screws
- close the back cover
- re-install right side skin with tabs in bottom and snap into place
- put the toner cartridge back in and close the top toner door
Testing
- - Put printer into offline mode (press online/offline button)
- - Press menu button until "test menu" appears
- - Press "next/index button" until "self test" appears
- - Press "Enter" to run the self test and print out an info page
- - Leave test page in output tray and put printer in store (LJ4 = $70, 4plus/4Mplus = $80?)
Most common problems
- rubber rollers on exit transport are shiny and smooth (z-fold paper jams)
- main drive gear running the fuser is broken or missing teeth
- the front pick roller is dirty or smooth
- the lower feed roller is dirty or smooth (rotate the rubber band)