HP LJ 8000 2,000-Sheet Tray Stand-Alone Tests

The second-generation Tray 4 (Model No. C4781A) has a stand-alone tests feature. Unlike the first-generation Tray 4 (Model No. C3763A for the LJ 5Si), the new Tray 4 can be manually powered on and put into any one of three tests. The rear cover must be removed for access to the power supply switch lever, and the test selection DIP switch on the logic PCA.

The three tests are motors test, sensors test and running test.

Motors Test

>Switches 1, 2 and 4 on.
>Drawer open. The test will not run if the drawer is closed.
>The VTU can be open or closed.
>Power switched on. There's about a two second delay before the test starts.
>All three motors run constantly. The deck elevation motor runs to no effect because the drawer is open. (Rotation is counterclockwise as viewed from the back.)
>The VTU's electromagnetic clutch is kept energized, so the lower roller should be turning constantly.
>The pickup solenoid is kept energized, so there's a constant clicking noise from the cycling pickup mechanism.

Sensors Test

>Switches 3 and 4 on.
>Drawer and VTU open.
>Power switched on.
>Actuating any sensor toggle or switch lever causes the LED on the logic PCA to illuminate. This is an excellent test for finding unreliable paper size sensing switches. Each switch closure should be sensed with only enough pressure applied to its lever to cause it to click over. Any switch that requires extra pressure to cause the LED to go on is likely to give intermittent trouble.

Following are all the items that can be tested:

>Each of two paper quantity switches.
>Each of four paper size switches. (Note that these switches are also the means by which a 'drawer closed' condition is sensed. There is no physical paper size configuration that doesn't result in at least one switch being actuated.)
>Top-of-stack/deck-floor sensor.
>Paper out sensor.
>VTU open/closed sensor.
>VTU entry sensor.
>VTU exit sensor.

Running Test

>Switches 1 and 4 on.
>Paper in drawer and drawer closed.
>VTU closed.
>Power switched on. There's about a two second delay before the test starts.
>The VTU motor runs briefly, then stops.
>The deck is elevated.
>The tray commences picking up and feeding sheets up and out the VTU. 'Easiest way to stop the test is to open the VTU; then you'll have to clear a stalled sheet or two out of the works. The test will restart if you close the VTU.

Error Conditions

Error conditions are reported by way of long and short LED flash sequences. There's a table of them inside the rear cover of the unit.

Closing Up

Don't forget to set all four DIP switches to off. Note that the power switch lever is constructed in such a way that installing the rear cover forces the lever to its normal position.

HP LJ 8000 Vertical Transfer Unit (VTU) Teardown

The following applies to the VTU for 2,000-Sheet Tray Model No. C4781A

The VTU is off the 2,000-Sheet Tray.

1) Mechanism out of Shell
>Four M3x8mm black pan head threading screws.
>NOTE: For the following step, do not use the spring-loaded, hinged flap as a handle for lifting out the mechanism. Damage may result (e.g. stretched springs).
>Two claws along the front side and two claws at the lower side.

2) Black Plastic Clutch Cover
>One claw visible up top.
>One downward-gripping claw at the lowest corner of it. This claw can be obstinate. Pry as you press the claw upward.

3) Ty-Wraps
>Cut three of four. Mark where they were with a Sharpie.

4) Motor Mount w/Motor
>Three M3x6mm bright washerhead screws.

5) Two Large Tandem Gears

6) Clutch
>One e-clip.

7) Bronze Bearing by Clutch
>One e-clip.

8) Gear at Other End & Bronze Bearing
>One e-clip, gear, loose pin, bearing.

9) Flap
>Two springs.
>Take the flap off the roller.

10) Lower Roller

11) Upper Roller
>Two e-clips.
>Gear.
>Loose pin.
>Two bearings.

12) Upper Idler Gear
>One e-clip.
>NOTE that the extended hub goes inboard.

13) Lower Idler Gear
>One e-clip.
>NOTE that the extended hub goes outboard.

14) Sheet Metal Chute
>Four M3x6mm bright washerhead screws.
>You'll have to lever each hinge away slightly to free the chute.
>At reinstallation, mind the upper sensor's lever -- it must be swung into its opening.

15) Lower Pinch Roller
>E-clip and gear at front side.
>Loose pin.
>E-clip.
>The bearings can remain in place and be cleaned in situ. Note that they're easily dislodged in the outboard direction, though.

16) Upper Pinch Rollers

HP LJ 4/4+ PC LOAD LETTER Message

The same message, PC LOAD LETTER, appears for either a paper out condition, or a tray out condition. PC LOAD PAPER when there is paper in the tray is caused by the cassette size sensing switches on the Paper Control PCA.

Try giving the switches a good WD-40 soak accompanied by many actuations. If the switches can't be revived by that, replace the Paper Control PCA.

HP LJ P3005 -- Gear Kit P/N KIT-P3005-GR

The kit consists of four gears. Worn teeth on these gears cause a great deal of noise.

1) Single flanged gear, 19t, 6.5mm bore. Rearmost lower position.

2) Tandem 17t/17t w/claw, 6mm bore. Rearmost upper position.

3) Single flanged gear, 20t, 5.5mm bore. Forward lower position.

4) Tandem 20t/20t, 7mm major bore. Forward upper position. (The bore diameter is reduced at one end. It's not possible to get the gear on its spindle the wrong way around.)

- The fuser must be removed for access to the gears. See this post for instructions.

- The gear at the forward lower position (item '3' above) is the one that wears the most.

- BE CAREFUL with the retaining clip at the forward upper postion. It's very easy to drop it into the works when removing it, and create a big dismantling job for yourself to retrieve it.

- The illustration (Figure 7-3) in the parts section of HP's service manual is incorrect. Items '16' and '19' are transposed from their actual locations.

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