Monday, October 17, 2011

HP LaserJet 40X0 -- Routine Teardown/Overhaul

What follows is for a basic LaserJet 4000 with a single 500-sheet Tray 2.

1) Cartridge

2) Tray 2

3) Tray 2 Rear End Cover, if present

4) Fuser End Caps
- Tug their lower edges out and up.

5) Back Door
- Open it and pry at the right side hinge to free the door.

6) Fuser
- Two captive screws.

7) Rear Right Side Cover
- Tug it rearward to remove it.

8) Control Panel Overlay
- Pry at its right side lip to free two small claws.

9) Control Panel
- Pry up its front edge and two claws will let go. If the claws don't let go readily, you may need to coax them individually; they're down at either side near the front.
- One cable connection.

10) Top Cover
- Two M4x12mm bright pan head threading screws at the back.
- Two M4x12mm bright pan head threading screws under the toner cartridge access door.
- Cartridge engagement arm -- free its upper end.
- Pry at the right front to free the right front corner.
- Tug the front of the cover up forcefully to free it.
- NOTE: The door's hinges are easily separated to facilitate washing the door and cover.

11) Front Right side Cover
- One claw at the top.

12) Left Side Cover
- One claw high up rear of centre.

13) Tray 1 Door
- Pry gently to free the inner platform from its ways.
- Slide the door rightward off its hinges.

14) Tray 1 Platform w/Sensor Arm Cover and Torsion Spring
- Torsion spring. (Not present on early machines. Later machines have a torsion spring associated with the right side hinge.) Free it from the underside of the platform.
- Tug forcefully on the sensor arm cover to pop it off the pickup shaft.

15) Two Black Extended Head Screws near the Front
- The left side screw is visible by the violet cable for Tray 1's paper-out sensor.
- The right side screw is concealed under the envelope feeder's connector cover. Open the cover and you'll see the screw's head.

16) Tray 1 Pickup Assembly w/Left Side Cartridge Guide
- One in-line cable connection for the pickup solenoid.
- One cable connection for the paper-out sensor.
- Five M4x12mm black pan head threading screws in front. Four of them are in deep wells.

17) Paper Feed Assembly
- One in-line cable connection.
- Two M4x10mm black pan head threading screws. NOTE that these are in the upper holes of the brackets. The two lower holes are where two of the Tray 1 pickup assembly's screws go.

18) Cover-Open Switch Bracket
- One M3x6mm bright pan head screw w/captive star washer at blue ground wire terminal.
- One M4x10mm black pan head threading screw forward of and below the previous screw.
- Free the bracket and let it dangle by the side of the machine.

19) Registration Assembly
- One M3x6mm bright pan head screw w/captive star washer at the extreme right.
- NOTE. There is another M3 screw forward of and to the left of the previous screw. DO NOT loosen it.
- Five M4x10mm black pan head threading screws.
- Overhaul per this post.

20) Pre-Transfer Ground Plate
- Lift it out.

21) Delivery Assembly
- The left side white bearing unhooks easily and lifts out.
- The right side bronze bearing has a lever on it. Swing the lever up to vertical and the unit can be lifted out.
- Overhaul per this post. (Scroll down to "To dismantle...".)

22) Printhead
- Three cable connections.
- Four M4x12mm black pan head threading screws.

23) Formatter Cage
- Four M3x6mm bright washerhead screws. (Early machines had a fifth screw at the top.)
- Tug the cage rearward to disconnect it.

24) Formatter Cage Receiver (Sheet Metal)
- Four M4x10mm black pan head threading screws.
- Three M3x6mm bright pan head screws w/captive star washers or washerhead screws.

25) Fourteen-Conductor Cable Connector
- Unplug it and free it from its hook.

26) One M4x10mm Black Pan Head Threading Screw
- It's at the left side, just below and behind the lower rear corner of the fan.

27) Engine Chassis
- It's free to be lifted off the paper tray module.

28) Tray 2 Top Cover
- Two M3x6mm black pan head screws.
- Seven M4x10mm black pan head threading screws.

29) Tray 2 Pickup Assembly
- One M3x16mm black pan head threading screw, very low down in a notch at the right side.
- NOTE: The screw was deleted from later production.
- One two-conductor cable connection. Free the black cable from its restraints.
- Clean/replace rollers A/R.

30) PCA Cover
- Two claws at the top edge.

31) PCA
- Two cable connections.
- Two claws.
- Apply WD-40 to the pushbutton switches and actuate them many times. Blow them out w/compressed air.

32) Blow out and clean the base A/R.

33) Reassemble the tray module.

34) Blow out the engine's chassis with compressed air.

35) Reinstall the chassis on the tray module.

36) Reassemble from step '26)'.

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