Fujitsu DL6400/6600 -- Fatal Error Alarms

The DL6400/6600 reports a fatal error by flashing its PAPER OUT LED, and turning on one or two FONT LEDs. There are thirteen possible alarm conditions, but only twelve alarm indications. (A ROM checksum failure doesn't produce an alarm indication.) Following are the alarm names, a brief description of each and, in square brackets, their corresponding FONT LED indicator(s). (This information is directly from Fujitsu's service manual; I haven't verified its accuracy.)

1) Power. The +40V power supply's output is low. [COUR 10]

2) Left End. The Left End Sensor (LES) failed to detect carriage arrival at the left end of its travel. [PRESTG 12] (See this post for more on this one.)

3) Overload. The +40V power supply is overloaded. [COMPRESS 17]

4) RAM. A read or write error has been detected. [BOLD PS]

5) ROM. A ROM checksum error has been detected. [Apparently, this condition does not produce an alarm indication. The service manual is unclear about what the error indication is. It says, "The program enters an infinite loop." Your guess is as good as mine as to what that looks like.]

6) FAN. The fan is inoperative. [N. SANS PS]

7) HEAD. There's a fault in a printhead driver circuit. [DRAFT 10]

8) SP Motor. A space motor (carriage motor) fault has been detected. [DRAFT 12]

9) LF Motor. A line feed motor fault has been detected. [MENU FONT]

10) GAP. There's a fault in the automatic gapping mechanism. [COUR 10 + COMPRESS 17]

11) Ribbon Motor. A ribbon motor fault has been detected. [COUR 10 + BOLD PS]

12) Jam Lever. The jam lever is open. [COUR 10 + TIME PS]

13) CSF Motor. A Cut Sheet Feeder motor fault has been detected. [COUR 10 + N. SANS PS]

# # #

Lexmark 931 through 935 Errors

Errors 931 through 935 are all printhead (laser/scanner) faults. Printhead unit replacement is the only solution. No service parts are available for the printheads.

Replacement printheads are costly, and what you get as a replacement part is likely to be a unit salvaged from an out-of-service printer, not a new unit from the factory.

On balance, when a T-Series printer starts getting printhead errors, you're well advised to write the machine off and replace it. It's likely to become a costly headache if you choose to repair it.

# # #

Fujitsu DL6400/6600 -- Setting Top of Form (TOF)

For fine incremental forward paper motion, hold ONLINE and press LF/FF.

For fine incremental reverse paper motion, hold ONLINE and press TEAR OFF.

To save your TOF position once you're satisfied with it, press ONLINE and LOAD both together.

# # #

Fujitsu DL6400/6600 -- Left End Alarm

Symptom: The PAPER OUT LED is flashing. The PRESTG 12 LED is on solid. The machine is inoperative.

Meaning: The above is a "left end alarm". The Left End Sensor (LES) failed to detect carriage arrival at the left end of its travel during the POST routine.

Possible cause: The cover interlock switch at the right front corner of the chassis isn't making. A brief explanation is in order.

The DL6400/6600 has two access cover interlocks:

a) On the upper edge of the control panel, there is a Hall-effect switch that's triggered by a permanent magnet embedded in the access cover. That device's output is a logic signal that merely informs the controller of the access cover's open/closed status.

b) At the upper right front corner of the chassis, there is a microswitch that's physically actuated by a plunger on the access cover. That switch is a safety feature. It disables the carriage drive circuitry when the cover is open. If the switch fails to make, the effect on the printer is loss of carriage motion. Hence the carriage can't get to its home position. Hence the machine reports a "left end alarm".

The microswitch is actuated indirectly via a spring-loaded pivoting paddle. In the case I came across, the actuator had gotten swung backwards and hung up on its bracket so it couldn't reach the switch. It just needed to be forced back into its correct at-rest position so it could operate as it should.

So, anytime you see a "left end alarm" on a DL6400/6600, examine the interlock switch first.

# # #

Fujitsu DL6400/6600 -- Fan Replacement

The following is for replacement of the main fan that's in the right side vertical chassis member. DL6600s have an additional fan for cooling the power supply. Access to it is gained the same way.

- - -

1) Access Cover

2) Control Panel
> Three downward-gripping claws at its upper rear.
> One cable connection.

3) Top Cover
> Two M4x10mm bright pan head screws w/captive washers at the back.
> Tip the cover up at the rear and pull it away. MIND THE CONTROL PANEL CABLE as you do this.

4) Mechanism Tilted Up
> The mechanism is not fastened at the rear. It can be tipped up and propped in position for access to the fan. There should be a prop rod held by two clips at the right side of the chassis pan.
The prop anchor hole is at the rear, just left of the Interface PCA. If the rod is missing, use a suitable screwdriver for a prop.

5) Fan
> Cable connection 'CNFAN'.
> Two M3x30mm YZD pan head screws w/captive washers.
> Air flow direction is outward.

# # #

Lexmark T640 -- Developer Drive Access/Overhaul

A machine that's had a serious toner-fouling incident will likely need to have its developer drive assembly removed, cleaned, lubricated and reinstalled. Following is the access procedure and the teardown/overhaul procedure specific to a T640. All prior 'S' and 'T' series machines are very similar. Machines with separate engine-controller/formatter architectures won't confront you with a mass of cables to be unplugged as the T640 does.

- - -

1) Left Side Cover
> Two finger-operable claws at the front. Swing it open far enough and its upper hinge will pop apart harmlessly for removal.

2) System PCA Enclosure Cover
> Loosen off six M3x6mm pan head screws.
> Slide the cover forward slightly and pull it away over the screw heads.

3) System PCA w/Enclosure
> Twenty or twenty-one cable connections, depending on model.
> There may be a ty-wrap to be cut on one of the printhead cables.
> Free the cabling from the enclosure's cable openings.
> One M3x15mm hex washerhead screw at the PCA's upper rear corner.
> Three M3x10mm washerhead threading screws. They're near the PCA's three other corners.
> The item is free to come away from the chassis.

NOTE: Before proceeding, observe the interaction of the developer drive assembly's pivoting cartridge engagement lever, and the plastic lever that's linked to the access door's hinge. Note that the engagement lever is inboard of the plastic lever.

4) Developer Drive Assembly
> One M3x28mm pan head screw at the lowermost position.
> Two M3x8mm pan head threading screws.
> The item is free to come away. NOTE that there is a loose drive coupling hub, along with a clip-fit drive coupler, between the developer drive and the main drive. NOTE their relationship.

- - -

Proceed as follows to dismantle the developer drive assembly:

1) Loose Drive Coupling Hub

2) Clip-Fit Drive Coupler

3) Lever Return Spring

4) Lever
> One e-clip.
> Withdraw the pivot pin upward.

5) Triaxial Self-Aligning Coupler
> One e-clip.
> One flat washer.
> Coupler body.
> Spring.
> Gear w/drive spline.

6) Large Idler Gear
> One e-clip.

The remaining gear is a snap-fit item that's best not removed.

Clean all components with Varsol in a parts washer.

Lubricate the gear spindles with WD-40 on reassembly.

Lubricate the coupler's flat washer and e-clip area with light mineral oil. Do not use grease anywhere.

# # #

Lexmark T640 System PCA Access

The T640 has its engine control and formatter functions combined on a single PCA, the System PCA. Proceed as follows to remove it.

1) Left Side Cover
> Two finger-operable claws at the front. Swing it open far enough and its upper hinge will pop apart harmlessly for removal.

2) System PCA Enclosure Cover
> Loosen off six M3x6mm pan head screws.
> Slide the cover forward slightly and pull it away over the screw heads.

3) System PCA w/Enclosure
> Twenty or twenty-one cable connections, depending on model.
> There may be a ty-wrap to be cut on one of the printhead cables.
> Free the cabling from the enclosure's cable openings.
> One M3x15mm hex washerhead screw at the PCA's upper rear corner.
> Three M3x10mm washerhead threading screws. They're near the PCA's three other corners.
> The item is free to come away from the chassis.

4) Option Slot(s) PCA (aka Interconnect PCA)
> Two M3x6mm pan head screws.

5) System PCA
> Five M3x6mm pan head screws: two at the parallel interface connector; one at the USB connector; two through the System PCA.
> NOTE: At reassembly, don't tighten the two screws through the System PCA until the three interface connector screws are in place and tight.

# # #

Lexmark Tray Bias Roller

Just inside the Tray 1 cavity, at the right side, there's a roller mounted in a spring-loaded arm; that's the Tray Bias Roller. It keeps Tray 1 shoved (biased) leftward to align it with the chassis and to assure reliable operation of the auto size sensing feature. It also serves as a detent pawl to hold the tray in its closed position. The rollers occasionally acquire a flat spot and need to be replaced. Here's a view of a flat-spotted roller, with a new roller to its right. (You have to transfer the spring to the new part.)



Beginning with the Optra S and continuing on through the T630, the service replacement part was P/N 99A0026. On the T640, the P/N has changed to 40X0213. There is no dimensional/functional difference between the two parts that I can see, but P/N 40X0213 is considerably less expensive than P/N 99A0026. (This is not the first time I've seen a gross inconsistency in Lexmark's parts pricing.)

The thing to do, obviously, is to order and stock only the T640 part, P/N 40X0213.

- - -

To replace one of these, remove the cartridge, tray 1, the redrive assembly and the right side cover. The front end of the spring is hooked onto an anchor post very near the front of the printer. Here's a view of that.

Get a firm grip on the straight section of the spring with long-nose pliers and you can unhook the spring from its anchor post. Note the spring's path through the chassis member as you extract it. Transfer the spring to the new part, thread the spring back through and anchor it. Confirm that the roller arm's pivot-point is correctly seated before buttoning up the printer.

# # #

FEEDBACK

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HP LJ P3005 -- Formatter Access

1) Right Side Cover
> Force it rearward a bit to free it.

2) Formatter Cage Door
> Tug it open and lift to remove it.

3) Formatter PCA
> Three cable connections.
> Six M3x8mm pan head screws w/captive washers.
> The PCA is free to come out.
> NOTE that there's a lithium button cell on the board. Mind where you set the board down so as not to short it.

# # #

HP LJ P3005 -- Engine Test

The engine test pushbutton is well hidden. Remove the right side cover by forcing it rearward. About 1 1/2" below the bottom-front corner of the fan grille there's a small round hole. Poke in there to operate the switch.

Press and release for a single print. If you hold down the switch, the test will print pages continuously until the switch is released.

The test print is horizontal lines.

# # #

Lexmark T-Series High Voltage Power Supply (HVPS) Access

The following procedure is specifically for the T63x machines, but all of the T models prior to the T650 (and even the old Optra S) are very similar. On the T650, the HVPS is directly behind the right side cover; it's much easier to get at.

Here's a view of the HVPS in a T642. The T64X HVPS has been failure-prone (917 errors).

Proceed as follows:

1) Toner Cartridge

2) Paper Tray (Tray 1)

3) Redrive Cap
- Lift it up at its right side end to remove it.

4) Back Door
- Open it to about 30º from vertical and you can pull it away off its hinges.

5) Redrive Assembly
- Two M4x8mm pan head thread-rolling screws.
- Two outward-hooking claws, left and right side, high up.

6) Right Side Cover
- One M3.5x10mm pan head threading screw from high up inside the redrive cavity.
- One M3.5x10mm pan head threading screw from inside the cartridge cavity.
- One claw at the front just above the MP Feeder.

7) MP Feeder Door/Platform
- Open it to about a 45º angle and it can be pulled off its flatted hinge pins.

8) Upper Deflector
- Pull the extreme left end of the piece toward you and force the deflector to the right. It can then be unhooked at the right end.
- NOTE that reinstallation of this item is complicated by a downward-projecting spike near its left side end. You really have to flex the thing to get it to go back into place.

9) MP Feeder Pick Roll
- One claw. Don't over-deflect it. It's easily snapped off. In the event of a claw snapping off, a small (3") ty-wrap works fine as a retainer.

10) MP Feeder Lower Deflector/Elevator Flap Assembly
- NOTE 1: This item is easily removed, but can be awkward to get back in place. Before proceeding, note carefully the relationship between the MP Feeder’s pickup cycle cam, and the cam follower that’s integral with the Elevator Flap. Keeping that relationship in mind at reassembly will be helpful.
- NOTE 2: At reinstallation, wipe off the face of the separation pad with methyl hydrate prior to putting the pickup roller back on its shaft.
- One M3.5x8mm pan head threading screw at the solenoid's base.
- Two M3.5x12mm pan head threading screws at the right side.
- Two M3.5x8mm pan head threading screws at the left side.
- Force the flap to open fully.
- Remove the spring.
- Dislodge the sensor cable and the sensor.

11) Inner Deflector
- Two tabs at lower front, left and right.
- Two upward-hooking claws near the upper rear; accessible through rectangular openings.

12) HVPS
- One spade terminal at the right rear. It can take a fair bit of force to get it off with pliers.
- One cable connection at the left front.
- Two M3x6mm pan head screws at the front.
- Pry up the PCA slightly at its right rear corner to free it from a small stud, and pull it leftward to free it.

# # #

FEEDBACK

# # #

HP LJ P2015 Formatter Access

There's not much to it.

1) Tray 2 out.

2) Front Door open.

3) Left side Cover
> Pry near the top and bottom at the rear edge. The rear edge will pop free and you can unhook the front edge.

4) Formatter PCA
> Five cable connections.
> Four M3x6mm black washerhead screws.

# # #

Oki PM 3410 -- Paper Unloads Instead of Parking

Symptom: Paper is in position, loaded from a bottom push tractor-feed unit. The user presses 'PARK' and the paper unloads completely instead of parking.

The bottom feed paper-out sensor is likely hung up on a paper shard; the machine can't tell when the paper has gone past the sensor. A good blow-out of the chassis with compressed air will often clear it up. If it doesn't, you'll have to make a visual confirmation that the sensor is toggling normally and is undamaged. If all appears to be ok mechanically, a check of the sensor's electronic signal output is in order (often much easier said than done). Failure of sensors' electronics is extremely rare, though.

Generally, whenever you encounter this symptom from whichever paper path, it's a binding paper-out sensor that's causing it.

# # #

Lexmark Autocompensator Retraction Bellcrank (aka 'Spring Arm Bellcrank')

The bellcrank is available as a service replacement part, P/N 56P1228. Proceed as follows to replace a broken one.

1) Tray 1 and Cartridge out. Set the machine on its back.

2) One E-Clip at the right side end of the autocompensator's pivot rod.

3) One M3x6mm pan head screw at the rear of the autocompensator's frame.

4) Unhook cabling A/R.

5) Slide the autocompensator assembly rightward to free the left side end of the rod. The assembly can then come away from the printer's chassis.

6) Bellcrank
- Force the broken part off the the end of the rod with a pair of Channellocks.
- NOTE that the protruding spring-hook portion of the bellcrank must go to the right.
- The bellcrank is a snap-fit onto the shallow groove in the rod. It must end up as far to the left on the rod as the flat portion of the rod will allow it to go.
- A 5/16" nutdriver can be used as a 'punch' to get the bellcrank started onto the rod with a light hammer blow.

7) Attach the spring to the new bellcrank and reinstall the autocompensator assembly. Here's a view of the bellcrank fully installed.



Springs

There are four different springs used with the bellcrank, depending on tray capacity and whether it's an integral tray or an add-on.

• 250-Sheet Add-On Spring P/N 99A1929.
• 250-Sheet Integral Spring P/N 99A1927.
• 500-Sheet Add-On Spring P/N 99A1928.
• 500-Sheet Integral Spring P/N 99A1930.

# # #

FEEDBACK

# # #

HP LJ 2200 -- False Paper Out

Symptom: Flashing amber LED. Paper in Tray 2. Manually operating the paper-out sensor's toggle makes the machine come ready.

It's possible for the paper level indicator lever to get dislodged and interfere with the paper platform's upward travel. Then, even though there's paper in the tray, the platform can't raise it high enough to actuate the paper-out sensor's toggle.

Simplest solution is to delete the indicator lever. To gain access, remove the front of the tray by prying two tabs out of their notches. ( The tabs are on top at the left and right sides, about 1 1/2" back from the front face of the tray.) The lever can be manoeuvred out frontward once the front of the tray is off.

# # #

Oki 393 Tractor Phasing

Tractor phasing in the Oki 393 is correct when the following conditions obtain:

a) The timing marks (holes) in the two gears are directly facing one another.

b) The timing marks on the two large round sprockets are facing rearward.

c) The timing marks on the tractor-drive sprockets are facing forward.

Any time you have the tractors dismantled, take the opportunity to dab the sprockets' timing marks with Liquid Paper. They'll be a lot easier to see when they're in the machine.

Verify the tractor phasing by loading one sheet of tractor-feed paper, and hand cranking it toward the large round sprockets. The pins on the large sprockets should mesh perfectly with the paper coming from the tractors.

# # #

Oki 393 Menu Mode

The Oki 393's control panel has no sub-legends for the menu mode key functions. Following is a summary of the 393's menu mode functionality (continuous forms loaded is assumed):

To enter menu mode from power off:

• Press and hold 'QUIET' while powering on.

To enter menu mode while powered on:

• Deselect.
• Press 'QUIET'.

The key functions while in menu mode are:

• List All -- 'QUIET'
• Group -- 'LINE FEED'
• Item -- 'FORM FEED'
• Set -- 'TOP OF FORM'
• Exit -- 'SELECT'

# # #

Terminology -- Laser/Scanner Assembly vs. Printhead

Since early days, we've been accustomed to the term 'laser/scanner assembly' (often just 'scanner') for the item in a printer that provides the laser beam scanning and modulation to write a latent electrostatic image on a drum. But with the advent of so many multifunction machines with document scanners on them, confusion begins to creep in when one says 'scanner'.

That points up the wisdom of Lexmark's choice of the term 'printhead' for laser/scanner assembly. The term is unambiguous, and can't be miscontrued as having anything to do with a document scanner.

So, throughout the posts here, I'll use the term 'printhead' for the laser/scanner assembly in any make of printer.

# # #

HP LJ 2420 Printhead Access

1) Cartridge

2) Tray 2

3) Rear Cover/Door Assembly
> Pull the rear door fully open.
> Two M4x10mm pan head threading screws.
> Two claws within the tray 2 cavity.

4) Formatter Cage Cover
> Force it rearward a bit to free it.

5) Left Side Cover
> Two M3x8mm bright washerhead screws in the handgrip cavity.
> One forward-hooking claw inboard at the upper rear. It’s high up in a rectangular well.
> Two downward-hooking claws at the underside.
> There are two concealed, inaccessible, downward-hooking claws at the top. Tug away at the rear and pry at the top to force those two claws to unhook.

6) Mains Receptacle Bezel
> Treat as if hinged at its outboard long edge.
> There’s a single downward-hooking claw about 3 3/8" below its top edge. If the item is stubborn, slide a thin tool in behind it about 4" below its top edge and move the tool upward. You’ll unhook the claw.

7) Top Right Rear Corner Cover
> One M3x6mm black washerhead screw at the rear.

8) Top Cover
> Four M3x6mm black washerhead screws.
> NOTE that at reinstallation, the front edge of this cover must be hooked in place before lowering it into place.

9) Black Plastic Air Duct Cover P/N RC1-4128
> One claw.

10) Printhead
> Two cable connections.
> Four M3x8mm bright washerhead screws.

To open the printhead for cleaning, there's one M3x8mm pan head threading screw on top and four tabs. With the top cover off the printhead, there's a safety-interlock shutter that's free to fall out.

# # #

Lexmark 924 Error

'924 Service' is an open fuser thermistor error. Replace the thermistor.

On later models, with the fuser out of the machine, the thermistor is readily accessible; no disassembly of the fuser is required. The Optra S and some early 'T's needed the fuser's top cover to be removed in order to replace the thermistor.

The thermistor is at the upper front of the fuser, near the left side end. On later models it's held in place with a single M3x10mm pan head screw w/captive washers. It has a two-conductor cable that runs back to the fuser's PCA. Early machines had pushnuts for cable restraints -- the pushnuts can be coaxed off by using a scriber point as a fine prybar. Later machines have open hook-restraints.

A good thermistor exhibits a room temperature resistance reading of approximately 400 kohms. The resistance falls with rising temperature (negative temperature coefficient). You can see the effect on an ohmmeter just from the warmth of your hand. The thermistor's resistance provides the engine controller's logic with an analogue of fuser temperature. An open (infinite resistance) thermistor renders the fuser inoperative; hence the fatal 924 error very early on in the printer's POST.

# # #

Lexmark T63X Routine Teardown/Overhaul

[NOTE: There's a condensed, 'checklist' version of this document here.]

Following is our standard procedure for an in-shop overhaul of a T63X series printer. The procedure assumes a machine that's basically in working order, but in need of a teardown, a thorough cleaning and a fuser overhaul.

The developer drive, main drive and the paper alignment assembly are left undisturbed; they normally don't require attention. In cases of severe toner spillage, those items do need to be removed and cleaned/overhauled.

PRELIMINARIES:

1) Auto Size Sensing; Tray Bias Roller
- See this post for information on checking and servicing the auto size sensing feature.
- Inspect the tray bias roller that's just inside the tray cavity at the right side. The roller must be free spinning and have no flat spots. Flat-spotted rollers must be replaced. The part is accessible once the right side cover has been removed. See this post for more information.

2) Maintenance Count
- To view the accumulated page count since the last time anyone cleared it, press and hold the 'Select' and 'Return' keys while powering on. That invokes the CONFIG MENU where you can check and clear the maintenance count. Clear the maintenance count after you're done testing the completed machine.

3) Page Count
- The page count and the permanent page count can both be found in the DIAGNOSTICS menu within PRINTER SETUP. To invoke the DIAGNOSTICS menu, press and hold the 'Go' and the 'Return' keys while powering on.

4) Error Log
- The error log is an item in the DIAGNOSTICS menu.
- When there are items in the error log, note what they are. They're usually just paper jams and the like. The presence of printhead errors calls for printhead replacement. The machine is likely to be written off because of the high cost of the part.
- Clear the error log after you're done testing the completed machine.


ORDER OF WORK:

1) Toner Cartridge
- Machines seldom come into the shop with a toner cartridge. When they do, be sure to note it and label the cartridge so it goes out with the printer. If the cartridge has a defect, it should still go out with the printer, but clearly labelled that it's defective.

2) Paper Tray (Tray 1)
- Check that the backstop is linked to the size sensing key and is operable. When set for letter size paper, the two lower sensing fingers should protrude, the upper finger should be retracted.
- The four black ramps in front must be clean. Trays that have been used for sheets of labels are liable to have label adhesive muck fouling the ramps. Clean A/R with Varsol and/or methyl hydrate.
- Examine the pass-thru slot at the front of the tray for stuck labels or damage.

3) Redrive Cap
- Lift it up at its right side end to remove it.
- One or both of the two prongs that secure this part is/are often broken. P/N is 99A2074.

4) Fuser Cleaning Wand Cover

5) Fuser Cleaning Wand
- NOTE that the felt strip is removeable and reversible.
- In place of a cleaning wand, there is often an item that's just a cover for the cleaning wand cavity. It will have a small handle at its centre. The handle goes to the rear.

6) Paper Support
- Tip it up and pull it off its hinges.

7) Back Door
- Open it to about 30º from vertical and you can pull it away off its hinges.
- Check that the duplexing deflector's torsion spring is in place and correctly hooked at its ends. The deflector must pivot freely, and return smartly to its at-rest position when released.

8) Redrive Assembly
- Two M4x8mm pan head thread-rolling screws.
- Two outward-hooking claws, left and right side, high up.
- Check that the output diverter is in place in its bearings and spring-loaded.
- Check that the duplex diverter push-rod is properly fastened and free moving. If the little fasteners/glides show any sign of being loose, apply a drop of CA adhesive to cement them in place permanently.

9) Left Side Cover
- Two finger-operable claws at the front. Swing it open far enough and its upper hinge will pop apart harmlessly for removal.

10) Right Side Cover
- One M3.5x10mm pan head threading screw from high up inside the redrive cavity.
- One M3.5x10mm pan head threading screw from inside the cartridge cavity.
- One claw at the front just above the MP Feeder.

11) MP Feeder Door/Platform
- Open it to about a 45º angle and it can be pulled off its flatted hinge pins.
- If this item is really filthy, it can be easily dismantled for washing. There are just the three obvious M3x8mm pan head threading screws holding it together.

12) Fuser
- Power cable in-line connection.
- Signal cable connection at PCA.
- Two M4x8mm pan head screws w/captive washers.

13) Power Supply Output Connector Cover
- One M3x6mm pan head screw.

14) Power Supply
- Two M3x6mm pan head screws at the rear.
- Slide the unit rightward far enough that you have access to the output cable connection.
- Output cable connection.
- Slide the unit rightward far enough that you have access to the fuser power cable connection.
- Fuser power cable connection.
- Slide the unit rightward fully out.

15) Control Panel Clear Cover and Overlay
- Pry gently at its upper edge.

16) Cartridge Access Door w/Latchbar and Spring
- One M3.5x10mm pan head threading screw.
- Two M3.5x10mm pan head threading screws w/captive washer.

17) Top Cover
- NOTE: At the upper right rear corner there is a screw w/captive washer that need not be removed. The tab it’s associated with is not actually fastened in place by the screw.
- One M3.5x8mm threading screw at the right side -- it’s a bit tucked away below the rearward curve of the cover.
- Three M3.5x12mm threading screws w/captive washer.

18) Main Fan Grille
- NOTE: This part has two small locating studs underneath that are easily broken if the part is levered off crookedly. Pry the grille up gently to avoid breaking the studs.
- Wide end goes over fan; narrow end forward.

19) System PCA Pan Cover
- Loosen off six M3x6mm pan head screws.
- Slide the cover upward slightly and pull it away over the screwheads.

20) PTO Cover
- One M3.5x8mm pan head threading screw.

21) Upper Deflector
- Pull the extreme left end of the piece toward you and force the deflector to the right. It can then be unhooked at the right end.
- Check for any accumulation of label adhesive muck on the item's undersurface. Clean with Varsol and/or methyl hydrate A/R.
- NOTE that reinstallation of this item is complicated by a downward-projecting spike near its left side end. You really have to flex the thing to get it to go back into place.

22) MP Feeder Pick Roll
- One claw. Don't over-deflect it. It's easily snapped off. In the event of a claw snapping off, a small (3") ty-wrap works fine as a retainer.
- Blow off the paper dust and clean the tire with lacquer thinner.

23) MP Feeder Lower Deflector/Elevator Flap Assembly
- NOTE 1: This item is easily removed, but can be awkward to get back in place. Before proceeding, note carefully the relationship between the MP Feeder’s pickup cycle cam, and the cam follower that’s integral with the Elevator Flap. Keeping that relationship in mind at reassembly will be helpful.
- NOTE 2: At reinstallation, wipe off the face of the separation pad with methyl hydrate prior to putting the pickup roller back on its shaft.
- One M3.5x8mm pan head threading screw at the solenoid's base.
- Two M3.5x12mm pan head threading screws at the right side.
- Two M3.5x8mm pan head threading screws at the left side.
- Flap Spring.
- Optical Sensor -- unhook it and let it dangle.

24) Pick Rolls
- If early-style pick rolls (40X0070) are in place, the retaining claws can easily be deflected too far and snapped off. Later-style pick rolls (40X4308) were redesigned to preclude that happening.
- If reinstalling early-style pick rolls, note the arrows on the hubs indicating direction of rotation. Only the later-style pick rolls should be used as service replacements. See this post for more information.
- Check the operation of the one-way clutch that's integral with the pick roll axle. It should turn freely in the feed direction; lock in the opposite direction.

25) Inner Deflector
- Two tabs at lower front, left and right.
- Two upward-hooking claws near the upper rear; accessible through rectangular openings.

26) White Glide
- It just slides out to the right.

27) Transfer Roller
- Pry up by its left side bearing to free it.
- Handle the roller with a paper towel. Avoid touching the roller's surface.
- NOTE that the gear goes to the right side.
- Blow off any toner. The shaft ends that ride in the bearings should be immaculately clean. Use Varsol and/or methyl hydrate sparingly to clean them.

28) Charge Roller
- Handle the roller with a paper towel. Avoid touching the rollers' surface.
- Clean only by blowing off.
- It's all but impossible to judge a charge roller's fitness for service by its appearance. Only a print test will show if it's satisfactory.

29) Post-Transfer Paper Deck
- Two outward-hooking claws underneath at front left and right.
- One M3x8mm pan head threading screw at the ground wire terminal.

30) Blow out Chassis. Blow out four optical sensors.

31) Printhead
- Inspect the printhead's output 'window' for dust or debris. A flashlight and a mirror from a lady's makeup compact are helpful. It's sometimes possible to blow off the window by flexing the 'straw' of a duster can to point up at it. If that doesn't work, unfasten the printhead and flip it over to clean the window thoroughly. NOTE the following before loosening any screws:
- There are three screws to be removed. There's a fourth screw daubed with red varnish that shouldn't be disturbed.
- At the screw at the right front, take a sharp HB pencil and trace the perimeter of the screw's captive washer so as not to lose the factory-set position of the printhead.
- Three M3.5x12mm pan head threading screws w/oversize captive flat washers.

32) Paper Feed Alignment Gearing and Drum Drive Gear -- inspect and clean gear teeth A/R.

33) MP Feeder Pickup Clutch -- lubricate sparingly with WD-40.
- Apply the WD-40 at each end of the clutch's control collar so it can wick down into the clutch spring.

34) PTO Vertical Shaft -- pack grease around its two bearings.

35) Transfer and Charge Roller Bearings
- Clean these with a Q-Tip and Varsol followed by methyl hydrate.
- The bronze bearings especially should be immaculately clean. No lubricant of any kind is to be applied to them or to the plastic bearings at the left side.

36) Reassemble the machine back through item '13)', the power supply output connector cover. Install the MP Feeder Door/Platform, the left and right side covers and the paper support.

37) Wipe the paper tray's slide ledges with WD-40. Fill it with paper and install it in the printer.

38) Install the cartridge. Set the machine aside.

39) Overhaul the fuser per the procedure.

40) Complete the reassembly of the machine.
- Fuser.
- Redrive Assembly.
- Back Door.
- Fuser Cleaning Wand.
- Fuser Cleaning Wand Cover.
- Redrive Cap.

41) Test operability.

42) Clear the error log.

43) Clear the maintenance count.

44) Remove paper from tray 1.

45) Remove the cartridge if it doesn't belong to the machine.

46) Install a bubble-pack restraint under the charge roller.

47) Tape the front of the machine shut.

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FEEDBACK

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Oki 320/1 Turbo, 420/1 Line Feed Losses

Symptom: The vertical print position on continuous forms creeps upward.

Cause: Worn/damaged gear teeth on the change gear.

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Here's a view of the gear-train.


The rearmost gear (right side of the photo) is the tractor drive gear. Those usually last the life of the printer.

Below and in front of the tractor drive gear is the tandem change gear that provides friction/tractor-feed selection. In front of that gear is the idler gear.

The change gear leads a hard life, and is prone to getting chipped teeth -- random line feed losses ensue. Here's a close-up of a change gear with a missing tooth.

The damage to a tooth needn't be that severe for line feed losses to occur. Even slight tooth damage that can barely be seen will cause trouble so, when the symptom shows up, replace the change gear and the idler gear just in front of it.

Change Gear P/N 51228001.

Idler Gear P/N 51238501.

Remove the reset leaf spring and the tractor drive gear. (One side of that gear's square hub is a claw that holds the gear on the shaft.)

Remove the idler gear and the change gear. (NOTE that the idler's extended hub goes inboard; the change gear's small end goes outboard.) Clean their spindles.

Grease the spindles and the gears' bores liberally. Do not grease the gears' teeth; grease on the teeth will just attract and retain paper dust. Grease the reset leaf spring's working surfaces.

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Wear in the gears' bores will cause the same symptom as damaged gear teeth do. Gear mesh has to be full and flawless for this gear train to work reliably

On printers that have seen long, hard service, the change gear's spindle may be worn, and even new gears won't provide reliable line feeding -- the worn spindle results in marginal gear mesh. The only solution is to replace the chassis. That's actually quite doable, but it does take a complete teardown and transfer of components.

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FEEDBACK

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CA (Cyanoacrylate) Adhesive

Commonly known as Krazy Glue or Super Glue, CA adhesive is indispensable in the workshop. Following are a few brief points about it:

a) It bonds skin instantly. The stuff can be dangerous.^[1]

b) Dollar stores carry it. I've found the dollar store stuff to be perfectly good for my purposes, and considerably less expensive than the brand name products.

c) There's a gelled version available, but I really can't imagine why. One of the adhesive's biggest virtues is that it's extremely runny. It will wick into the tiniest gap or crevice.

d) Runny though it is, it can be made to 'build' with repeated applications. That can be very helpful in the restoration of rusty old machinery; small unwanted crevices can be filled with it. The resultant fill can be filed or sanded, is impervious to water or oil and can be painted.

e) Further to its use as a filler, I've read that you can fill a larger gap with baking soda, then apply drops of CA. I've yet to have tried this myself. I suspect that pungent fumes result when it's done. Some types of applications result in fumes, and this is likely one of them.

f) It's not terribly heat resistant. LePage's website advises that immersion in boiling water can soften cured adhesive, so it's likely unsuitable for any application that will subject it to temperatures approaching 100° C. That said, you can safely use it as a threadlocker, or for any machinery assembly application that may need to be taken apart again. Just as with threadlockers, sufficient heat will soften it.

g) Its water and chemical resistance is impressive. I've read that acetone will soften it. Apart from that, though, the stuff seems to stand up to just about anything.

h) Keep it in the fridge. Heat, light and humidity all tend to thicken it. Kept in the fridge, a tube of it will stay fresh and runny; you'll get the use of all of the tube's contents.

i) I've read that if it gets on cotton, it generates a lot of heat as it sets, enough heat to be dangerous.

j) There are many specialized versions available, but you have to go to industrial supply houses for them. So far, I've gotten by fine with the common variety. There's much more information about the material available on the web.

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Note:

[1] There's a flipside/upside to this.

If you're plagued, as I am, by splits in fingertip skin through the winter months, CA adhesive is a therapeutic. The instant you acquire a fingertip skin split and notice the attendant pain, seal the split with CA adhesive. The pain stops. The split is cleanly sealed against infection and can heal from beneath undisturbed.

I've read that some individuals may find the adhesive irritating and consequently useless for this, but it works for me.

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FEEDBACK

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HP LJ 2420 Gear Kit P/N KIT-24xx-GR-NN

The kit consists of three gears:

1) Narrow, rearmost 19t gear P/N RU5-0379.

2) Wide, upper-frontmost 21t gear P/N RU5-0377.

3) Lower-frontmost 20t gear P/N RU5-0378.

Item '3)' is the one that leads a hard life and wears out, making for a noisy gear train.

Each gear is held on its spindle by a claw -- they're easily removed. Replace all three. Grease the teeth. Lubricate the spindles with WD-40.

HP LJ 2420 Fuser Access

The 2420's fuser is not user-replaceable, but it's not difficult to get at and replace.

There's a set of three gears that should be replaced whenever a fuser is replaced. You have full access to them once the fuser is out. The set of gears is P/N KIT-24xx-GR-NN. See this post for more infromation.

Proceed as follows to remove the fuser:

1) Tray 2

2) Rear Cover/Door Assembly
> Pull the rear door fully open.
> Two M4x10mm pan head threading screws.
> Two claws within the tray 2 cavity.

3) Mains Receptacle Bezel
> Treat as if hinged at its outboard long edge.
> There’s a single downward-hooking claw about 3 3/8" below its top edge. If the item is stubborn, slide a thin tool in behind it about 4" below its top edge and move the tool upward. You’ll unhook the claw.

4) Black Plastic Cover at Left Side (Your right.)
> One claw/latch -- it has a ‘handle’ extending rearward.
> Pull the cover toward you. A spring hook is helpful.

5) Fuser Power Cable
> It's at the lower right just below the line cord receptacle.

6) Exit Sensor Cable (Violet)

7) Thermistor Cable (Yellow and white.)
> Free the cable from its white restraint. The restraint can be unlatched with a fingernail or a small screwdriver.

8) Duplexer Input Ramp
> Two claws -- they have ‘handles’ extending rearward.
> Push up on the claw handles and pull the ramp toward you.

9) Fuser
> Three prominent M4x10mm pan head threading screws.
> One M3x6mm pan head screw w/captive star washer. It’s in a recess at the fuser’s lower right.
> Tug on the power cable and the green wheel to coax the fuser out the back.

HP LJ 1320 -- Flashing Amber LED; Motor Doesn't Run

A flashing amber LED on the 1320 can mean any of several things, but when the motor doesn't run at all it's a giveaway that the cover interlock switch is not being made. The interlock actuator is a rectangular plastic projection at the upper-left corner of the toner cartridge access door. The projection is about 5/8" long, long enough that it's a bit fragile and easily bent over rightward by a careless user.

In the instance we encountered, we were able to bend the projection back to straightness without it breaking off.

Terminology -- Circuit Boards

The terminology in this industry is a bewildering mess of ill-conceived and sloppily applied terms. Nowhere is that more evident than with respect to the major circuit boards typically found in laser printers. I'll attempt to clarify the subject here.

First, though, we need to clear away some clutter.

The terms 'board', 'circuit board', 'logic board', 'printed circuit board (PCB)' and 'printed circuit assembly (PCA)' all mean the same thing -- a thin, flat, usually rectangular piece of insulating material with conductive traces and electronic comonents and connectors on it. I'm partial to 'PCA' (Printed Circuit Assembly), and in writing I always use that term following a circuit board's name; e.g. Formatter PCA or DC Controller PCA. With that out of the way, let's get on with engine controllers and formatters and system boards and the like -- they're the source of much confusion.

Early Days -- The LaserJet II and Lexmark 4019

In any monochrome printer, there are two distinct functions at work. One is engine (mechanism) control; the other is page composition.

In the LaserJet II, engine control was done by the DC Controller PCA; page compositon was done by the Formatter PCA.

In Lexmark's 4019, the engine control and page composition functions were combined on a single PCA -- the System PCA.

Engine Control PCAs

HP has been fairly consistent with the use of DC Controller PCA for the engine control PCA's name.

Lexmark has made models with separate engine control and page composition PCAs. For those machines, Lexmark uses the term Engine Controller PCA, not DC Controller PCA.

HP uses the term Engine Controller PCA as well, but they reserve its use for PCAs that have the engine control function and the power supplies combined on them. Many of HP's modern crop of compact machines are constructed this way.

Formatter PCAs

Formatter PCA continues to be HP's term for a page composition PCA.

Where Lexmark has made machines with separate engine control and page composition PCAs, they've used the term RIP PCA for what HP calls a Formatter PCA. 'RIP' stands for 'Raster Image Processor'. (If you're familiar with the operation of CRT displays, you'll certainly recognize the term 'raster'. Laser printers employ rasterization as well.)

Main Logic PCA

'Main Logic PCA' is liable to mean System PCA or Formatter PCA or RIP PCA. It's a term that's best avoided, really, but it does crop up.

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