The bezel has to come off before the control panel can be removed, but the arrangement is a bit deceptive. Proceed as follows:
a) In back of the hinged access cover you'll see two black claws that secure the upper part of the control panel. Release those, and the upper edge of the control panel with the bezel still attached can come away from the cover a bit.
b) Tug/pry the upper edge of the bezel upwards at the left and right corners of the control panel. The bezel's upper edge will come free.
c) Lever the bezel's upper edge outward far enough and its two lower claws will pop free.
d) A single screw secures the lower edge of the control panel.
Tuesday, March 16, 2010
Friday, February 5, 2010
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.
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.
Tuesday, February 2, 2010
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
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
Monday, February 1, 2010
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.
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.
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.
# # #
# # #
Thursday, January 28, 2010
HP LJ 5Si Registration Assembly Teardown
Orientation: For this procedure, 'right end' is the clutch end. The unit is right side up on the bench in front of you.
1) Clutch
>One e-clip.
2) Two Tension Springs
3) Upper Bronze Bearings (6mm bore)
>Two e-clips.
4) Upper Roller w/Flap
>NOTE: Take care not to distort the ground continuity strap at the left end. It's hooked onto the edge of the frame.
>Remove roller from flap.
>Remove gear from roller.
>REASSEMBLY NOTE: Ensure that the clear mylar strip on the flap ends up on top of the roller, not under it, and ensure that the ground continuity strap is hooked back in place.
5) Left End Lower Roller Gear
>One claw.
6) Lower Bronze Bearings (8mm bore)
>Two e-clips.
7) Lower Roller
>It's free of the frame once the two bearings are off,.
>Remove its gear.
8) Scrub gears and bearings with Varsol. Air dry.
9) Clean the rollers with lacquer thinner.
10) Clean remaining parts as required.
11) Inspect/Service the clutch per this article.
12) Reassemble. Check that all screws are snug.
13) Lubricate the bronze bearings with light mineral oil.
1) Clutch
>One e-clip.
2) Two Tension Springs
3) Upper Bronze Bearings (6mm bore)
>Two e-clips.
4) Upper Roller w/Flap
>NOTE: Take care not to distort the ground continuity strap at the left end. It's hooked onto the edge of the frame.
>Remove roller from flap.
>Remove gear from roller.
>REASSEMBLY NOTE: Ensure that the clear mylar strip on the flap ends up on top of the roller, not under it, and ensure that the ground continuity strap is hooked back in place.
5) Left End Lower Roller Gear
>One claw.
6) Lower Bronze Bearings (8mm bore)
>Two e-clips.
7) Lower Roller
>It's free of the frame once the two bearings are off,.
>Remove its gear.
8) Scrub gears and bearings with Varsol. Air dry.
9) Clean the rollers with lacquer thinner.
10) Clean remaining parts as required.
11) Inspect/Service the clutch per this article.
12) Reassemble. Check that all screws are snug.
13) Lubricate the bronze bearings with light mineral oil.
Electromagnetic Clutches
The single-plate electromagnetic friction clutch is one of several types of clutch used in printers. Some are permanently assembled units that can't be dismantled for servicing, but many can be easily taken apart, inspected, cleaned and reassembled.
The example I'll use here is the registration clutch in the HP LJ 5Si. It's made by the Ogura Clutch Company. (Their website has a lot of interesting information.)
Characteristics and Failure Mechanisms
The clutches work by applying an electromagnetic field to a steel rotor that forms one face of a disc clutch. When the electromagnet is energized, the rotor becomes magnetized and attracts its mating clutch plate to itself, thereby engaging the clutch.
The clutches are meant to engage instantaneously when energized, and remain engaged with no slippage until de-energized. Typically, the clutches become troublesome when contaminants accumulate on the clutch faces, interfering with prompt, slipless engagement. Symptoms of this are often intermittent. The registration clutch in the 5Si can cause paper jams, misregistration and misregistration accompanied by paper fold-over. Intermittent paper jams are the most common symptom of clutch trouble.
Outright electrical failure such as a winding going open is extremely rare, and easily confirmed, if suspected, by a continuity test with an ohmmeter. The winding of the 5Si's registration clutch has a DC resistance of about 203 ohms. Any given clutch's winding will exhibit some characteristic normal value of DC resistance, depending on its design parameters. An 'open circuit' reading indicates a winding failure -- replace the clutch. A resistance reading significantly lower than normal would indicate an internal short circuit in the winding due to an insulation failure; cause for clutch replacement as well. Again, though, winding failures are rare.
Clutch Service
You'll need a small mechanic's vise to press the clutch back together after dismantling it.
The clutch is held together by two bronze washers that are press-fitted onto the ends of its rotor. Note the following points:
>The washers have a dead flat side, and a slightly chamfered side. The dead flat side goes outboard.
>The washers' outer faces are flush with the ends of the rotor. There is a fair bit of axial play in a properly assembled clutch. That play is normal and necessary.
>Methyl hydrate is a good cleaning solvent here as it leaves no residue whatsoever. The gear is often filthy and needs to be scrubbed with Varsol. Follow that with a methyl hydrate scrub and a blow-off. Never leave the gear to soak in solvent for any period of time.
Pry off the bronze washers and the clutch is apart. Clean the gear as noted above. The magnetic ring on the inner face of the gear is there to cause prompt disengagement when the clutch is de-energized. If it has come free of the gear, replace the clutch. It might be possible to bond the magnetic ring back onto the gear with CA adhesive, but I've not had occasion to try that yet.
Clean the plate, the rotor and the rotor's plastic sleeve bearings with methyl hydrate. (Replacement sleeve bearings are not available; if the bearings are badly worn the clutch must be replaced.) Ideally, your shop should have an air compressor for blowing off components to ensure dust-free assemblies.
When all is satisfactory, press the bronze washers back on one at a time. With the washers on flush with the rotor's ends, you're done. The clutch is fit to go back in service.
Permanently Assembled Clutches
Permanently assembled units are much better protected from contaminant incursion than the serviceable unit dealt with above, but they are by no means 'sealed'.
It's possible to flush them somewhat with a squeeze squirter bottle of methyl hydrate, then thoroughly blow them dry with compressed air. Were that to improve the operation of a suspect clutch, it would at least tell you that the clutch must be replaced.
MONDAY, MARCH 15, 2010
Addendum
'Had a clutch failure last week in an HP LJ 8000; it was the second pass roller's clutch in the paper input unit. It gave quite a set of symptoms:
The example I'll use here is the registration clutch in the HP LJ 5Si. It's made by the Ogura Clutch Company. (Their website has a lot of interesting information.)
Characteristics and Failure Mechanisms
The clutches work by applying an electromagnetic field to a steel rotor that forms one face of a disc clutch. When the electromagnet is energized, the rotor becomes magnetized and attracts its mating clutch plate to itself, thereby engaging the clutch.
The clutches are meant to engage instantaneously when energized, and remain engaged with no slippage until de-energized. Typically, the clutches become troublesome when contaminants accumulate on the clutch faces, interfering with prompt, slipless engagement. Symptoms of this are often intermittent. The registration clutch in the 5Si can cause paper jams, misregistration and misregistration accompanied by paper fold-over. Intermittent paper jams are the most common symptom of clutch trouble.
Outright electrical failure such as a winding going open is extremely rare, and easily confirmed, if suspected, by a continuity test with an ohmmeter. The winding of the 5Si's registration clutch has a DC resistance of about 203 ohms. Any given clutch's winding will exhibit some characteristic normal value of DC resistance, depending on its design parameters. An 'open circuit' reading indicates a winding failure -- replace the clutch. A resistance reading significantly lower than normal would indicate an internal short circuit in the winding due to an insulation failure; cause for clutch replacement as well. Again, though, winding failures are rare.
Clutch Service
You'll need a small mechanic's vise to press the clutch back together after dismantling it.
The clutch is held together by two bronze washers that are press-fitted onto the ends of its rotor. Note the following points:
>The washers have a dead flat side, and a slightly chamfered side. The dead flat side goes outboard.
>The washers' outer faces are flush with the ends of the rotor. There is a fair bit of axial play in a properly assembled clutch. That play is normal and necessary.
>Methyl hydrate is a good cleaning solvent here as it leaves no residue whatsoever. The gear is often filthy and needs to be scrubbed with Varsol. Follow that with a methyl hydrate scrub and a blow-off. Never leave the gear to soak in solvent for any period of time.
Pry off the bronze washers and the clutch is apart. Clean the gear as noted above. The magnetic ring on the inner face of the gear is there to cause prompt disengagement when the clutch is de-energized. If it has come free of the gear, replace the clutch. It might be possible to bond the magnetic ring back onto the gear with CA adhesive, but I've not had occasion to try that yet.
Clean the plate, the rotor and the rotor's plastic sleeve bearings with methyl hydrate. (Replacement sleeve bearings are not available; if the bearings are badly worn the clutch must be replaced.) Ideally, your shop should have an air compressor for blowing off components to ensure dust-free assemblies.
When all is satisfactory, press the bronze washers back on one at a time. With the washers on flush with the rotor's ends, you're done. The clutch is fit to go back in service.
Permanently Assembled Clutches
Permanently assembled units are much better protected from contaminant incursion than the serviceable unit dealt with above, but they are by no means 'sealed'.
It's possible to flush them somewhat with a squeeze squirter bottle of methyl hydrate, then thoroughly blow them dry with compressed air. Were that to improve the operation of a suspect clutch, it would at least tell you that the clutch must be replaced.
MONDAY, MARCH 15, 2010
Addendum
'Had a clutch failure last week in an HP LJ 8000; it was the second pass roller's clutch in the paper input unit. It gave quite a set of symptoms:
- No paper jams, oddly enough, but paper folding noises just upstream of the second pass roller.
- Affected pages were correctly registered at the leading edge, had a blank band about 3" from the leading edge and were misregistered at the trailing edge (print going clear to the edge and beyond). The blank band area showed evidence of creasing.
The clutch must have been slipping at engagement time, so a sheet's leading edge would be stuck for awhile at the second pass roller while its trailing edge kept advancing. By the time the clutch engagement finally took, the paper had gotten a fold in it, and it got fed through the regisrtation roller and transfer stage that way. On reaching the fuser, the fold would get pulled out flat and the sheet would fuse and exit normally.
I dismantled the clutch and its clutch faces didn't look to be badly fouled, but one of the rotor's plastic sleeve bearings came out with the rotor, suggesting a lack of clearance in the bearing. That may have been adding sufficient drag to cause the clutch to slip.
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