HP Laserjet Printer Repair

HP Laserjet 4 and 5

Cleaning up HP LJ 4, 4plus and 4Mplus printers (could be for LJ5 printer too)

Disassembly

1. open up the cover, take out the toner cartridge and put it in a dark

place

1. take out the paper tray
2. take off the right side skin (carefully press in two tabs)
3. drop open the back cover (if you lose the spring, you can replace it

with a Bic pen spring)

1. Unscrew the 2 fuser screws and take out the fuser, check it for

wrinkles and dirt

1. 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
2. Take off the rear exit transport by pressing in the two small tabs

and lifting it out

1. take the top panel off the exit transport by pressing the tabs and

snapping off the top

1. take out the top roller and treat the thicker rollers with rubber

rejuvinator

1. snap the top back on and save for later reinstallation
2. Check the main drive gear in the back for broken teeth (it drives the

fuser)

1. Open up the memory door
2. Take off the small black panel on the front of the printer by

pressing its tabs together

1. Open up all internal panels and metal lids to check for paper

remnants

1. take off the left skin by pressing two tabs and lowering it to the

left

1. 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.

1. If broken, take off the single sheet feed tray
2. detach the upper half of the tray from the lower by carefully

squeezing together the two pivot points

1. take off the horizontal metal strip (with spring clip on left) (two

screws)

1. take off the bottom piece by carefully bending the plastic to sneak

out the two pivot points from their sockets

1. 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

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
   4. Re-install fuser with two screws
   5. close the back cover
   6. re-install right side skin with tabs in bottom and snap into place
   7. put the toner cartridge back in and close the top toner door

Testing

1. - Put printer into offline mode (press online/offline button)
2. - Press menu button until "test menu" appears
3. - Press "next/index button" until "self test" appears
4. - Press "Enter" to run the self test and print out an info page
5. - 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)