HP Laserjet Printer Repair

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HP Laserjet 4, 4plus, 4M, 4Mplus and 5/5M

Initial Test

  1. Check to see if toner cartridge and fuser are in printer, add paper
  2. Plug in and power on the printer and wait for power-on self test to finish, listed for grinding noises
  3. Run a diagnostic page
    1. Put into offline mode
    2. Press menu until "TEST MENU" appears
    3. Press item until "SELF TEST" appears
    4. Press enter to print the page
  4. Check page count and print quality
  5. If things look and sound okay, continue with Disassembly
  6. If bad noises or no printing happens, mark the printer for part salvage and repair


  1. open up the cover, take out the toner cartridge and put it in a dark place
  2. take out the paper tray
  3. take off the right side skin (carefully press in two tabs)
  4. drop open the back cover (if you lose the spring, you can replace it with a Bic pen spring)
  5. Unscrew the 2 fuser screws and take out the fuser, check it for wrinkles and dirt
  6. Take off the top of the printer:
    1. unscrew the two screws on the back of the printer FIRST!
    2. unscrew the one screw on top
    3. press in the two tabs and gently lift the top up and tilt it right
    4. unplug the user interface cable connecting the top to the printer
  7. Take off the rear exit transport by pressing in the two small white tabs and lifting it out
    1. take the top panel off the exit transport by pressing the tabs and snapping off the top
    2. take out the top roller and treat the thicker rollers with rubber rejuvinator
    3. snap the top back on and save for later reinstallation
  8. Check the main drive gear in the back for broken teeth (it drives the fuser)
  9. Open up the memory door for later blowing out
  10. Take off the small black panel on the front of the printer by pressing its tabs together (they exist on either side of the front panel clasp)
  11. Open up all internal panels and metal lids to check for paper remnants
  12. take off the left skin by pressing two tabs and lowering it to the left
  13. take off the right front panel with the cartridge slot in it
    1. be careful of the tab on the bottom of the printer as it breaks off very easily
    2. There are two internal tabs that need to be pressed down through a hole in the right side of the printer as well.
  14. If broken, take off the single sheet feed tray
  15. detach the upper half of the tray from the lower by carefully squeezing together the two pivot points
  16. take off the horizontal metal strip (with spring clip on left) (two screws)
  17. take off the bottom piece by carefully bending the plastic to sneak out the two pivot points from their sockets
  18. release the spring (on the left side) from the top plastic piece and remove it


  • Clean off both feed rollers with rubber rejuvinator (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


  1. 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
  1. Put front single sheet feed plastic parts back on
  2. put horizontal metal strip with left side spring clip back on
  3. clip the two plastic pieces back together
  4. snap the small black front cover back on
  5. snap the front right panel (with cartridge slot) back on
  6. reinstall left panel. Put base tabs in and snap into place
  7. screw the memory door shut
  8. Put the top back on:
    1. connect the user interface panel cable
    2. snap the top down onto the printer
    3. add one screw in front-top and two screws in back
  9. Re-install fuser with two screws
  10. close the back cover
  11. re-install right side skin with tabs in bottom and snap into place
  12. put the toner cartridge back in and close the top toner door


  1. Run another diagnostic page (see Initial test above)
  2. Connect to Linux PC and print a CUPS test page
  3. leave both pages in the printer, add a price and put it in the store or on the "for-the-store" shelf

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)

HP LaserJet 4L, 4P, 5P and 6P

Initial Test

  1. Check for paper and toner cartridge
  2. Power on the printer and run a diagnostic page
    1. 4L - press single button
    2. 4P - cycle through menu and print self-test page
    3. 5P/6P - press both buttons at same time
  3. If no nasty noises and page looks reasonable, continue with cleaning


  • Open up top cover, take out toner and put it in the dark
  • Take out the 4 screws on the top
  • Take off the left panel with the small clip (slide forward and comes off) (not 4L)
  • Take out the SIMMs, if any to prevent damage when rolling on its side (not 4L)
  • Take out paper tray
  • Take off the top cover
    • there are lips on the back, loosen up the front first
    • you might have to open up panels for the cover to lift off (rear door on 4L)
  • Take off the fuser cover, pinch the clip on the right and slide right. (not 4L)
  • Take out the 4 fuser screws (only 3 for 4L)
  • Take out the fuser, look for wrinkles and dings on the teflon roller and pressure roller
  • Inside the front-top, take out the upper paper guide screw and take out the paper guide.


  • Blow out the inside of the printer with compressed air and clean out the fan
  • Blow out the fuser and the removed upper paper guide (especially the white pulley)
  • Clean the black roller with alcohol or rubber rejuvinator
  • Clean off the initial rubber feed roller (squeeze clip to come off (not 4L))


  • Put the rubber feed roller back on and make sure the clip clicks in (not 4L)
  • Put the front paper guide back in and put in screw
  • Put fuser back in and add 4 screws (3 for 4L)
  • Put the fuser cover back on and click to the left (not 4L)
  • Clean exit rollers
    • Use two small flathead screwdrivers to pry out and push up on white plastic clips
    • Wet rag with rubber rejuvinator and twist rollers in rag to clean off shinyness
  • Blow out the top case cover
  • Clean the case with Simple Green and rags or Scotch-Brite pad
  • Carefully put the top back on
    • corners should slide down into slots
    • snaps should go down into holes
    • Add 4 screws on top
  • Put the toner cartridge back in
  • Put the SIMMs back in (not 4L)
  • Put the left cover back on (slide on carefully and slide backwards to click and lock)(not 4L)
  • Clean the feeder roller on the bottom
  • Clean out the bottom with rag or blower
  • Put the paper tray back in

==Final testing

  • Print out another diagnostic page
  • Attach to Linux PC and print out CUPS test page
  • Bundle with wrapped up power cord and two test pages
  • Put in store or on "for-the-store" shelf

HP laserjet 1100

What the lights mean

<insert picture of printer lights here>