K
Service Source
LaserWriter 12/640 PS
K
Service Source
Overview
LaserWriter 12/640 PS
Overview About This Overview - 1
About This Overview
This overview briefly
describes the servicing
issues of the LaserWriter
12/640 PS, especially
those that distinguish it
from previous Apple laser
printers.
Overview General - 2
General
The LaserWriter 12/640
PS is a 600 dpi, 12 ppm
monochrome laser printer
that is positioned as the
workgroup laser printing
solution for Mac OS and
Windows users.
It features excellent print
quality, cross platform
support, and state-of-theart paper handling options.
LaserWriter driver 8.4
releases concurrently with
this printer.
Overview Options - 3
Options
There are three options that are available for the Laser-
LW 12/640 PS Options
Writer 12/640 PS:
• Duplexer unit
• Face-up catch tray
• 500-sheet feeder (accommodates either standard or
envelope cassette)
Each of the options can be added independently of one another
so there are several configurations that you might
encounter. The animation “LW12/640 PS Options” shows
how the options go together.
Overview Paper Path - 4
Paper Path
The printer has a basic S-shaped paper path and multi-
LW12/640 PS Paper Path
purpose tray arrangement generally similar to the LaserWriter 16/600 PS.
On the exit side of the fuser assembly, however, there is a
brand new function: the paper deflector guide. This
solenoid-actuated guide switches paper between one of two
paths. The inside path is the face-down delivery path that
continues straight up to the delivery rollers and output tray.
The outside path serves three purposes.
• Paper feed into the optional duplexer.
• Paper delivery to the optional face-up tray.
• If no options are attached, the outside path will feed
paper directly out the rear of the printer.
Note
: The “LW 12/640 PS Paper Path” animation shows
the sequence of a duplex print job.
Overview Duplexer - 5
Duplexer
The most unique mechanical feature you will encounter is
the optional duplexer unit. The term “duplex” denotes twosided printing.
The duplexer is an L-shaped feeder that cradles the
underside and rear of the printer. When duplex printing is
selected through software, the paper deflector guide is
actuated and the sheet of paper diverts into the duplexer.
There the paper is flipped and circulated back to the cassette
feed roller in preparation for its second imaging cycle.
The drive train in the horizontal leg of the duplexer receives
drive directly through an idler gear in the pickup drive
assembly in the printer. The feed roller at the entrance to
the duplexer also receives drive from the printer, but the
other feed rollers in the vertical leg of the duplexer are
driven by the duplexer motor.
Overview Sheet Feeder - 6
Sheet Feeder
An optional 500-sheet feeder is available. As with the
LaserWriter 16/600 PS design, the sheet feeder fits
squarely beneath the printer (or the duplexer, if present)
to form a dual front-loading cassette arrangement. An
envelope cassette is available for the sheet feeder only.
The feeder has a receptacle connector that mates with the
printer and has its own circuit board. However, the feeder
does not have its own motor. Instead it derives mechanical
drive directly from the gear train above, either the pickup
drive assembly in the printer or the intermediate gear train
in the duplexer. There is a pickup roller and pickup
solenoid in the sheet feeder.
Overview Face-Up Tray - 7
Face-Up Tray
The face-up tray is an option that attaches to the rear of the
printer (or to the rear of the duplexer, if present).
This tray performs similarly to previous printers, except
that output to this tray is selected through software, not by
the setting of a lever. The presence of this tray is not sensed
by the controller.
Optional
Face-Up Tray
Overview Duplex Scan Anomalies - 8
Duplex Scan Anomalies
After side one prints during a duplex job, the paper parks
itself onto a horizontal shelf beneath the cassette. The
duplexer motor then reverses direction. The trailing edge of
the paper becomes the leading edge, and the paper exits the
shelf and continues the path toward side-two printing.
Order of Scanning
Duplex documents stack in the face-down delivery tray in
correct book order (with odd-numbered pages facing down).
To achieve this, page two is imaged during the first pass and
page one during the second pass.
Long Edge Binding
The reversing action of the duplexer flips the paper over
Long Edge Binding
Scan/Feed Directions
along its short axis. If you have chosen long edge binding in
Overview Duplex Scan Anomalies - 9
the software, the I/O controller flips the imaging data
accordingly to counteract the reversal of the paper. The net
effect is even-numbered pages scanned in reverse.
For example, page 2 of a portrait oriented job images right
to left from the bottom up. (This anomaly does not occur
with short edge binding). For this reason, be aware that
some skew or image cutoff symptoms may appear to be 180
degrees off from normally scanned pages.
Double-Page Batching
If there is enough buffer memory space available, the
controller will image a print job four pages (two sheets) at
a time. For example, the imaging order of an eight-page
document would be pages 2, 4, 1, and 3 (with sheets one and
two then being delivered), followed by pages 6, 8, 5, and 7
(with sheets three and four delivered). This batching
Sequence of
Double-Page Batching
feature maximizes throughput speed.
Overview Miscellaneous - 10
Miscellaneous
Fuser Pressure Roller
The fuser pressure roller provides an opposing surface to
the fuser heater roller, the same function as in previous
laser printers. However in the LaserWriter 12/640 PS,
this pressure roller is seated in the chassis and is not a part
of the fuser assembly itself.
Power Supply Assembly
The power supply assembly is a large multifunctional
circuit board located in the lower section of the engine. In
addition to the DC power supply functions that are common
in previous engines, this assembly also houses some sensors
and switches, as well as the high-voltage power supply and
various other functions.
Overview Miscellaneous - 11
Beam Detection
Laser beam detection occurs outside of the laser/scanner
assembly, in the start-of-scan (SOS) sensor located in the
mirror assembly.
Two Shutters
There are two laser shutters, one inside the laser/scanner
assembly and one covering the mirror assembly. Both are
actuated with the closure of the top cover.
Two "Exit" Sensors
Unlike previous printers, there are two paper sensors
downstream of the fuser assembly. The first is the fuser
exit sensor that monitors the exiting of paper from the fuser
assembly. The second is the delivery sensor that monitors
Overview Miscellaneous - 12
paper after it passes the deflection guide in route to facedown delivery on top of the printer.
One Fan
There is only one fan in this printer.
Support for Heavy Paper
The LaserWriter 12/640 PS supports throughput of 50 lb.
paper for simplex (single-sided) print jobs. You must
print from the multipurpose tray and choose face-up
delivery when using 50 lb paper.
RAM Upgrade
The LaserWriter 12/640 PS comes with 4 MB of RAM in the
righthand of two SIMM slots. This amount does not allow for
Overview Miscellaneous - 13
duplex printing nor does it enable PhotoGrade. Upgrades are
required if you want either of these additional features.
No SCSI
There is no SCSI support in the LaserWriter 12/640 PS.
Startup Page
The startup page is a single-sided page with a layout similar
to previous PostScript LaserWriter printers. The startup
page does report the presence of a duplexer or sheet feeder
but will not recognize the optional face-up tray.
Overview Miscellaneous - 14
Service Test Page
You may print a service test
page by jumpering
connector J101 on the I/O
controller board. Consequently, unlike previous
printers, the I/O controller
board must be installed to
run a service test page.
Overview Miscellaneous - 15
Top Cover Closure
The closing of the top cover initiates several more events
than in previous printers. They are listed below and are
described in detail in the “Principles of Operation” chapter.
• Actuation of cover interlock
• Opening of the laser shutter
• Opening of the mirror assembly shutter
• Latching of the top cover
• Pressing of the jam release plate
• Actuation of the toner cartridge latching mechanism
• Actuation of the fuser idler gear
K
Service Source
Principles of Operation
LaserWriter 12/640 PS
Principles of Operation Print Process - 1
Print Process
Print Process Overview
The print process consists of the stages shown below, during which a toner image forms on
the drum surface, transfers and then bonds to the paper. Each sheet of paper passes through
steps 4 to 6. During printing,the drum surface repeatedly cycles through steps 1 to 5, as
well as cleaning stage 7.
1
Charging
2
Exposure
Xerographic Cycle
Cycle repeats for the next print
3
Development
Paper Enters
4
Transfer
5
Discharge
7
Cleaning
Paper Exits
6
Fusing
1 Charging
Places a uniform density of negative electric charge onto the drum surface.
2 Exposure
Scans the drum surface with a thin beam of laser light that switches on and off according to
the video signal from the printer controller. This exposure forms an invisible electrostatic
latent image on the drum surface.
3 Development
Attracts toner onto the electrostatic latent image on the drum surface, thus forming a
visible toner image.
4 Transfer
Transfers the toner image from the drum surface to the paper.
5 Discharge
Enables the paper to come off the drum surface.
6 Fusing
Fixes the toner image to the paper.
7 Cleaning
Cleans the drum surface of any residual toner.
Principles of Operation Print Process - 2
Print Process Diagram and Paper Path
Laser Beam
1 Charging 2 Exposure
6 Fusing
Fuser
Roller
BCR
7 Cleaning
Drum
Cleaning
Blade
3 Development
CM Blade
Attraction Roller
Paper
4 Transfer5 Discharge
Pressure
Roller
Cleaning Blade
Fuser Roller
Pressure Roller
Detack Saw
Mirror Assembly
Transfer Roller
Toner Cartridge
CM BladeBCR
Laser/Scanner Assy
Drum Detack Saw
Transfer Roller Attraction Roller
Principles of Operation Print Process - 3
Print Process Description
1 Charging
During this stage, the drum surface receives a uniform negative charge.
Note
: The drum surface is made of a photoconductive material and the inner part of the
drum is made of a conductive material. This negative charge is actually placed onto the
outside surface of the photoconductor layer.
The charge is imparted by the bias charge roller (BCR) within the toner cartridge. The
BCR is a conductive roller in contact with the drum surface and is supplied with a discharge
voltage by the high-voltage power supply (HVPS). The discharge occurs through the small
gaps between the BCR and the drum. The discharge voltage is an AC voltage with a negative
DC voltage superposed. The negative DC voltage is about -330 V. The AC voltage varies
within the range of about 1.6 to 2.0 kVp-p with the discharge current since the AC current
is regulated to be constant.
Note
: Before this stage, the drum surface will have been given a uniform negative
charge relative to the inner conductor of the drum (see “Cleaning”).
High-Voltage
Power Supply
(HVPS)
AC
DC
CR
Bias Charge Roller (BCR)
Negative Charge
Positive Charge
Drum
Photoconductor Layer
Conductor Layer
Principles of Operation Print Process - 4
2 Exposure
During this stage, the laser beam scans across the negatively charged drum surface.
The laser beam is emitted from the laser diode in the laser/scanner assembly. This diode is
stationary. Its beam reflects off the face of a rapidly rotating scanning mirror, through a
correction lens, and outward off a stationary mirror which directs the beam onto the
surface of the drum.
The laser beam is modulated according to the video signal from the printer controller,
switched on when the video signal denotes a black pixel and off when it denotes a white pixel.
The laser beam that strikes the drum surface generates electron-hole pairs in the
photoconductor layer, exciting electrons to the conduction band and thereby creating holes
in the valence band. The electrons are attracted by the electric field and move toward the
inner conductor of the drum to flow into it. The holes move toward the outside surface of the
photoconductor layer and recombine with the negatively charged electrons at the surface to
decrease the negative charge at the surface. The resultant less-negatively charged parts
(parts whose potential has risen relative to the inner conductor) in the drum surface form
an invisible electrostatic latent image.
Electron
Photoconductor
Layer
Conductor Layer
Laser Light
Electron-hole pair
Recombination
Decrease of
Negative Charge
Principles of Operation Print Process - 5
3 Development
During this stage, the electrostatic latent image on the drum surface attracts toner and
forms a visible toner image.
The LaserWriter 12/640 PS uses nonconducting magnetic toner that readily transfers to
plain paper. The toner is supplied from the toner compartment to the attraction roller
positioned close to the drum within the toner cartridge. Because of its slight magnetism, the
toner is attracted to the surface of the attraction roller and is spread evenly into a very thin
layer by the charging and metering blade (CMB). This blade is made of silicone rubber. As
it comes into contact with the toner, the resulting friction imparts a negative charge onto
the toner particles.
The attraction roller is covered with a thin conductive sleeve. A development bias (DB)
voltage is applied to the conductive sleeve from the HVPS. The DB voltage is a negative DC
voltage with an AC voltage superposed. The DC voltage is about -250 V and the AC voltage is
about 1.7 kVp.
Since the attraction roller is kept at a potential of about -250 V DC relative to the
conductor layer of the drum, the parts of the drum surface with the full negative charge
have a lower electric potential than the attraction roller, and the parts with decreased
negative charge have a higher electrical potential.
Therefore, the negatively charged toner on the attraction roller is pulled only to those areas
of the drum with the decreased negative charge (since the attracting force of the positive
charge on the conductor layer of the drum is greater than the repelling force of the negative
charge on the drum surface, the toner is attracted in spite of the repelling force of the
negative charge). As the toner adheres, the negative charge of those parts increases because
of the negative charge of the toner, lowering the electric potential and increasing the
repelling force of those parts to decrease the resultant attracting force.
The AC voltage agitates the toner particles on the attraction roller surface and facilitates
toner release. The invisible electrostatic latent image on the drum surface is thus developed
into a visible toner image.
HVPS
AC
DC
Development Bias
2
Exposure
1
Charging
Conductor
Layer
Drum
Scanner
Irradiated Part of
the Drum Surface
3
Development
CM Blade
Attraction
Roller
Photoconductor
Layer
Negative Charge
Positive Charge
Negatively Charge Toner
Non-Charged Toner
Principles of Operation Print Process - 6
3 Development (cont.)
The change of the electric potential of the drum surface while the drum
surface passes through the charging to the development steps
0 V
¡
Development Bias
About -250 V
Bias Charge
About -330 V
Conductor Layer
of the Drum
The electric potential of the parts of the drum surface struck
a:
by the laser beam (the areas with decreased negative charge)
rises above the electric potential of the attraction roller.
The electric potential of the parts with decreased negative charge
b:
lowers as the toner is attracted.
c:
The degree of inclination of the line indicates the strength
of the force and the direction of inclination indicates the
direction of the force exerted on the toner particles.
b
a
¬
¿
Drum Surface
Attracting
c
c
Repelling
Attraction Roller
¿ Charged
¡ Exposed
¬ Developed
Principles of Operation Print Process - 7
3 Development (cont.)
The diagram below illustrates the change of the potential as the drum surface passes from
the charging through the development stages:.
Drum Surface Voltage
1 Charging
2 Exposure
3 Development
Electrostatic Latent
Image (Invisible)
-V
-V
-V
About -233V
Bias Charge
0
0
About -250V
Development Bias
Toner Image
(Visible)
0
Principles of Operation Print Process - 8
4 Transfer
During this stage, the toner transfers from the drum to the paper.
The bias transfer roller (BTR), referred to herein simply as the transfer roller, applies a
positive charge to the back side of the paper as it feeds between the roller and the drum. The
toner image transfers from the drum surface to the front side of the paper due to this
positive charge on the back side of the paper.
The paper is attracted by the negative charge induced in the inner conductor layer of the
drum by the positive charge of the paper and sticks to the drum surface.
Laser Beam
1 Charging 2 Exposure
3 Development
Drum
HVPS
Transfer Roller
TR
4 Transfer
Drum
Conductor Layer
Photoconductor
Layer
Paper
Transfer Roller
Negative Charge
Positive Charge
Negatively Charged Toner
Principles of Operation Print Process - 9
5 Discharge
During this stage, the paper comes off the drum surface.
The detack saw applies a negative charge to the back side of the paper to neutralize the
positive charge previously applied by the transfer roller. The force which attracts the
paper to the drum surface disappears, and the paper releases naturally from the drum due
to gravity.
Laser Beam
1 Charging 2 Exposure
3 Development
Drum
HVPS
5 Discharge
DS
4 Transfer
Paper
Detack Saw
Positive Charge
Negatively Charged Toner
Non-Charged Toner
Principles of Operation Print Process - 10
6 Fusing
During this stage, heat and pressure fix toner to the paper.
The toner image transferred from the drum surface to the paper is easily dislodged. To fix
the image to the paper, the paper is passed between the fuser assembly and a pressure
roller. The fuser roller applies the heat necessary to bond toner to paper and also supplies
rotational force to help pull the paper evenly through. The pressure roller, though neither
heated or mechancially driven, provides the surface against which the pressure and heat can
be evenly applied.
K
Service Source
Specifications
LaserWriter 12/640 PS
Specifications Introduction - 1
Introduction
Specifications information for this product can be found in this chapter and also in the Spec
Database, which you can access in one of three ways:
Ñ Launch it directly by double-clicking the Apple Spec Database runtime alias at the
top level of the Main Service Source CD.
Ñ Select "Apple Spec Database" from the Service Source drop-down main menu.
Ñ Click the Acrobat toolbar icon for the database, which is near the right end of the
toolbar with the letters "SP."
Specifications Engine - 2
Engine
Marking Engine
Laser
Speed
Life Expectancy (Printer)
Fuji Xerox P893 laser-xerographic
Type: Semiconductor laser GaAlAs
Wavelength: 780 nm
Output power: 5 mW
SimplexÑ12 pages per minute maximum using A4-size paper.
Actual speed depends on the images printed.
DuplexÑ8 pages per minute maximum using U.S. letter-size
paper. Actual speed depends on the images printed.
Average number of prints between failure is 180,000 pages.
Specifications Engine - 3
Life Expectancy (Toner Cartridge)
Printing Materials
Life expectancy is 6,000 pages when printing text documents with
average page coverage (5% black). An example of a 5% black
page coverage is a page consisting of double-spaced 14-point
courier type. Printing images and other graphics may impact
toner cartridge life expectancy.
16- to 28-pound laser-quality bond (60 to 90 g/m 2 ); up to
50-pound (190 g/m 2 ) stock when fed manually through the
multipurpose tray and delivered through the face-up output
tray. Accepts most textured and colored stock. Accepts mediumweight photocopier transparencies and labels. Envelopes can be
printed from the multipurpose tray or from the optional
envelope cassette (sheet feeder only).
The paper used should not scorch, melt, transfer material, or
release hazardous emissions when heated to 200¡ C (393¡ F)
for 0.1 seconds.
Specifications Engine - 4
Paper Sizes and Capacity
Supports U.S. letter, A4, B5, executive, and legal in the standard
paper cassette. The paper cassette holds 250 sheets of 20pound (75 g/m 2 ) paper. The multipurpose tray can hold up to
80 sheets of standard U.S. letter paper, and other paper sizes
from postcard up to U.S. legal. An optional 500-sheet cassette
is available that supports letter, A4, and U.S. legal-paper
sizes. An envelope cassette that can automatically feed up to 50
envelopes is also available. The envelope cassette is compatible
only with the 500-sheet feeder.
Specifications Engine - 5
Dimensions
Printer only
Height 9.5 in. 24.2 cm)
Width 15.9 in. (40.5 cm)
Depth 16.7 in. (42.4 cm)
Printer with optional duplex printing unit
Height 11.89 in. (30.2 cm)
Width 15.9 in. (40.5 cm)
Depth 20.47 in. (52.0 cm)
Printer with optional 500-sheet cassette and feeder
Height 14.0 in. (35.6 cm)
Width 15.9 in. (40.5 cm)
Depth 16.7 in. (42.4 cm)
Printer with optional duplex printing unit and 500-sheet
cassette feeder
Height 16.2 in. (41.1cm)
Width 15.9 in. (40.5 cm)
Depth 20.4 in. (52.0 cm)
Specifications Engine - 6
Weight
Voltage Requirements
Approximately 30 lb. (14 kg)
U.S.
103.5 to 126.5 VAC, 58 to 62 Hz
Europe/Australia
198 to 264 VAC, 48 to 52 Hz
Note
: The LaserWriter 12/640 PS printer does not contain a
universal power supply or fuser assembly.
Specifications Engine - 7
Power Consumption
Energy-saving mode
26 W
Standby average
100/120 V, approximately 125 W
220/240 V, approximately 120 W
Operating average
110/120 V, approximately 390 W
220/240 V, approximately 370 W
Maximum power consumption
110/120 V, approximately 790 W, 6.8 A
220/240 V, approximately 770 W, 3.5 A
Specifications I/O Controller - 8
I/O Controller
Microprocessor
ROM
RAM
AMD Am29040 30-MHz RISC microprocessor
4 MB (including 35 Type 1 fonts)
4 MB (expandable to 64 MB)
72-pin, 70 ns or less SIMMs are required. See ÒUpgradesÓ for
full information about possible configurations.
Specifications I/O Controller - 9
Ports
Resolution
LocalTalk
Parallel
AAUI Ethernet port with three protocols:
EtherTalk
Novell NetWare IPX (PSERVER or RPRINTER)
TCP/IP (BSD lpd)
External Ethernet transceivers available for:
Thin Coax (10BASE-2)
Twisted Pair (10BASE-T)
Thick Coax (10BASE-5)
(All ports/protocols simultaneously active)
Two-position communication switch
600 dpi
Specifications I/O Controller - 10
Grayscale Imaging
Languages
Standard
85 lines/inch dithered halftone, 101 gray levels
106 lines/inch dithered halftone, 129 gray levels
141 lines/inch dithered halftone, 73 gray levels
PhotoGrade (12 MB of RAM required)
85 lines/inch halftone, 201 gray levels
106 lines/inch halftone, 257 gray levels
141 lines/inch halftone, 145 gray levels
PostScript Level 2 (2015)
PCL5 (LaserJet IIID emulation)
Specifications I/O Controller - 11
Fonts on Disk
Sixty-four fonts are provided with the LaserWriter 12/640 PS,
including such fonts as ITC Avant Garde ¨ , ITC Bookman ¨ ,
Chicago, Courier, Delphian, Garamond Condensed, Geneva,
Helvetica ¨ , Helvetica Black, Helvetica Compressed, Helvetica
Narrow, Lubalin Graph, Lucida Bright, Machine, Monaco,
Nadianne, New Century Schoolbook, New York, Old English
Text, Onyx, Oxford, Palatino ¨ , Swing, Symbol, Times ¨ , ITC
Zapf Chancery ¨ , ITC Zapf Dingbats ¨ , and Zeal.
Specifications I/O Controller - 12
Fonts in ROM
PostScript
The following fonts are resident in the printer ROM:
AvantGarde Book, AvantGarde BookOblique, AvantGarde Demi,
AvantGarde DemiOblique
Bookman Demi, Bookman DemiItalic, Bookman Light, Bookman
LightItalic
Courier, Courier Bold, Courier BoldOblique, Courier Oblique
Helvetica, Helvetica Bold, Helvetica Bold Oblique, Helvetica
Narrow, Helvetica Narrow Bold, Helvetica Narrow
BoldOblique, Helvetica Narrow Oblique, Helvetica Oblique
NewCentury Schoolbook Bold, NewCentury Schoolbook BoldItalic,
NewCentury Schoolbook Italic, NewCentury Schoolbook Roman
Palatino Bold, Palatino BoldItalic, Palatino Italic, Palatino Roman
Symbol
Times Bold, Times Bold Italic, Times Italic, Times Roman
Zapf Chancery MediumItalic
Zapf Dingbats
Specifications I/O Controller - 13
PCL
The following PCL fonts are resident in the printer ROM:
Times Roman, Time Bold, Time Italic, Times Bold Italic
Univers Medium, Univers Medium Bold, Univers Medium Italic,
Univers Medium Bold Italic
Courier 12 pitch, 10 point Medium; Courier 12 pitch, 10 point
Bold; Courier 12 pitch, 10 point Italic; Courier 10 pitch, 12
point Medium; Courier 10 pitch, 12 point Bold; Courier 10
pitch, 12 point Italic
Line Printer Font 16.67 pitch, 8.5 point, Medium
Specifications Environmental Information - 14
Environmental Information
Operating Temperature
Operating Humidity
Storage (Toner Cartridge)
Storage (Printer)
50¡ to 90¡ F (10¡ to 32¡ C)
15 to 80 percent RH non-condensing
Temperature 32¡ to 95¡ F (0¡ to 35¡ C)
Humidity 15 to 85 percent RH non-condensing
Temperature 32¡ to 122¡ F (0¡ to 40¡ C)
Humidity 35 to 85 percent RH non-condensing
Specifications Finished Goods Accessories - 15
Finished Goods Accessories
Ethernet
Toner Cartridge
Printer Options
Apple Ethernet Thin Coax Transceiver M0329Z/B
Apple Ethernet Twisted Pair Transceiver M0437Z/B
Apple Ethernet AUI Adapter M0432LL/A
LaserWriter 12/640 PS Toner Cartridge M4683G/A
LaserWriter 12/640 PS 500-Sheet Feeder M4682G/A (includes
standard 500-sheet cassette). Envelope cassette M4680G/A is
also available for the sheet feeder.
LaserWriter 12/640 PS Face-Up Output Tray M4698G/A
LaserWriter 12/640 PS Duplex Printing Unit M4697G/A
Principles of Operation Print Process - 11
7 Cleaning
During this stage, any residual toner on the drum is cleaned off to prepare for the next
print cycle.
The residual toner is collected in a special compartment separate from the fresh toner
compartment. The transfer rate is more than 90%, but varies according to the percentage
of printed pixels and the environmental conditions such as temperature and humidity.
Residual toner cannot be re-used.
BCR
Cleaning Blade
Toner Cartridge
Used Toner Drum
CM Blade
Attraction
Roller
Silicone Rubber
Principles of Operation Paper Transportation - 12
Paper Transportation
Paper Path Flowchart
The chart below shows the parts that feed paper through the LaserWriter 12/640 PS
engine. Parts are shown in the order in which they occur during a print cycle.
Pickup Roller
(Optional Sheet Feeder)
Cassette Feed Roller
Duplexer
Cassette Feed
Pickup Roller
Preregistration Feed and Pinch Rollers
Registration Feed and Pinch Rollers
Drum and Transfer Roller
Fuser Roller and Pressure Roller
Fuser Exit and Pinch Rollers
Manual Feed
Pickup Roller
Paper Deflector Guide
Duplexer and/or
Face-Up Delivery Tray
Delivery Rollers
and Pinch Rollers
Output Tray
Principles of Operation Paper Transportation - 13
Paper Path Diagram
The cross-sectional diagram below illustrates the elements indicated in the previous chart.
The roller diameters are listed below the diagram.
Delivery Roller Registration Pinch Roller
Delivery
Pinch Roller
Fuser Roller
Fuser Pinch Roller
Fuser Exit Roller
Pressure Roller
Drum
Transfer
Roller
Roller Diameter (inches/mm)
Delivery Roller
Drum
Registration Pinch Roller
Delivery Pinch Roller
Fuser Roller
Fuser Pinch Roller
Fuser Exit Roller
Pressure Roller
Transfer Roller
Registration Feed Roller
Cassette Pickup Roller
Cassette Feed Roller
Cassete Feed Pinch Roller
Preregistration Feed Roller
Manual Feed Pickup Roller
Preregistration Pinch Roller
Registration
Feed Roller
.34
1.18
.39
.39-.43
.89
31.0
.53
.90
.63
.56
.79
.55
.79
.55
.55
.63
Cassette
Pickup Roller
in. 8.8
30.0
10.0
10.0-10.8
22.6
8.0
13.6
23.0
15.9
14.3
20.0
14.0
20.0
14.0
14.0
16.0
Preregistration
Pinch Roller
Manual Feed
Pickup Roller
Preregistration
Feed Roller
Cassette Feed
Pinch Roller
Cassette Feed
Roller
mm
Principles of Operation Print Image Creation - 14
Print Image Creation
Print Image Generation
The image data signal (VIDEO) is sent from the I/O controller board to the laser/scanner
assembly via the DC controller board. The video signal is passed through the DC controller
board as received from the I/O controller without buffering or additional processing. The
signal is converted into laser light, which is scanned onto the surface of the photosensitve
drum as described below. As a result, an electrostatic latent image is produced on the drum
surface.
Mirror Assembly
Laser/Scanner
Assembly
Host Computer
Interface Cable
I/O Controller
Drum
J26
DC Controller Board
Principles of Operation Print Image Creation - 15
Laser/Scanner Assembly Structure and Operation
The laser light source used for the LaserWriter 12/600 PS is a semiconductor laser diode
(LD) with a rated maximum output power of 5 mW.
The laser diode is switched on and off according to the video signal. The power of the laser
light is monitored and controlled by the monitor circuit so that it remains constant.
The laser light from the diode is aimed directly at a hexagonal mirror that is being rotated
at a very high speed by the scanner motor. The six facets of the mirror reflect the laser
beam in turn as the mirror rotates.
The beam reflected by the hexagonal mirror passes through a correction lens and outward
from the laser/scanner assembly. The beam reflects downward off a stationary mirror and
through a slit in the toner cartridge, striking the surface of the photosensitive drum.
At the beginning of each scan, the laser beam strikes the start-of-scan (SOS) sensor. The
on and off switch of the laser light is determined by the signal from the SOS sensor.
Start-of-Scan (SOS) Sensor
Laser Diode Board
Hexagonal Mirror
Stationary Mirror
Drum
Correction Lens
Principles of Operation Print Image Creation - 16
Note
: One horizontal line of an image is drawn by scanning the pulsating laser beam
across the drum. The timing and location of the pulse is a function of the VIDEO signal
originating from the I/O controller board. By rotating the drum and scanning
additional lines, a two-dimensional image is built. The resolution of a laser printer is
determined by the number of pixels per inch (in the horizontal direction) and the
number of scans per inch (in the vertical direction). The LaserWriter 12/640 PS
has a resolution of 600 x 600.
Direction of Paper
600 scans/inch
600 dots/inch
Principles of Operation Mechanical Drive - 17
Mechanical Drive
The generation and transmission of mechanical drive in the LaserWriter 12/640 PS is
shown in the diagram below.
Pickup Motor
Main Motor
Gear cluster in the
pickup drive assembly
transmits the drive
force to the rollers
shown to the right.
Gear cluster in the
main drive assembly
transmits the drive
force to the rollers
shown to the right.
Cassette
Pickup Roller
Cassette
Feed Roller
Preregistration
Feed Roller
Manual Feed
Pickup Roller
Registration
Feed Roller
Photosensitive
Drum
Drive Transfer
Assembly
Transfer Roller
Fuser Roller
Delivery Rollers
Principles of Operation Mechanical Drive - 18
1 Pickup Motor Mechanical Drive (Part 1 of 2)
The drive force generated by the pickup motor is transmitted to the cassette and
preregistration feed rollers and to the cassette feed clutch gear via the pickup drive
assembly. The rotation of the cassette pickup roller is controlled by the cassette feed clutch
gear and the cassette feed solenoid.
Pickup Drive Assembly
Pickup Motor
Preregistation
Feed Roller
Cassette Feed
Clutch Gear
Cassette Feed Solenoid
Cassette Pickup Roller
Cassette Feed Roller20T Idler Gear
Principles of Operation Mechanical Drive - 19
2 Pickup Motor Mechanical Drive (Part 2 of 2)
The drive force generated by the pickup motor is also transmitted to the manual feed clutch
gear via the pickup drive assembly. The rotation of the manual feed pickup roller is
controlled by the manual feed clutch gear and the manual feed solenoid.
Manual Feed Solenoid Pickup Motor
Pickup Drive Assembly
Manual Feed Pickup Roller
Manual Feed Clutch Gear
Principles of Operation Mechanical Drive - 20
3 Main Motor Mechanical Drive (Part 1 of 3)
The drive force from the main motor is transmitted to the registration feed roller via the
main drive assembly.
Registration Pinch Roller
Registration Feed Roller
Main Drive Assembly
Main Motor
Principles of Operation Mechanical Drive - 21
4 Main Motor Mechanical Drive (Part 2 of 3)
The drive force from the main motor is also transmitted throught the main drive assembly
to the photosensitive drum, and from the drum to the transfer roller.
Photosensitive Drum
Main Drive Assembly
Transfer Roller
Main Motor
Principles of Operation Mechanical Drive - 22
5 Main Motor Mechanical Drive (Part 3 of 3)
The drive force from the main motor is also transmitted to the fuser roller drive gear and
the delivery assembly drive gear via the drive transfer assembly. When the toner cartridge
is removed, the idler gear opens the path of drive force transmission, thus cutting off
mechanical drive to the fuser assembly.
Toner Cartridge
Delivery Roller Shaft
Delivery Assembly
Drive Gear
Drive Transfer Assembly
Main Drive Assembly
Idler Gear
Fuser Roller
Drive Gear
Fuser Roller
Fuser Assembly
Main Motor
Principles of Operation Function of Major Components - 23
Function of Major Components
The function of the major components of the LaserWriter 12/640 PS is briefly described
below. The components are divided into the following seven blocks, which correspond to the
exploded views that appear in the exploded view chapter.
Cassette (Deck 1)
Paper Transport
Fusing and Paper Exit
Drive & Xerographic
Electrical
Frame
Cassette (Deck 1)
Paper Cassette
The cassette holds cut sheets of plain paper. Envelopes must be fed from the multipurpose
tray or the optional envelope cassette, and post cards must be fed from the multipurpose
tray.
The cassette has an adjustable paper guide at the left rear. By adjusting this rear paper
guide to the size of the paper used, individual actuator tabs on the left side of the cassette are
engaged, thereby actuating the corresponding microswitch on the cassette sizing assembly
board.
The cassette has a slot that allows passage of paper from the optional lower deck.
Cassette Sizing Assembly
Three paper size microswitches and the leaf spring actuator are mounted onto the cassette
size assembly printed circuit board.
Each microswitch is on when it is being pressed by the spring actuator. The size of paper
(or a no-cassette-present state) is detected by the combination of on and off switches.
Principles of Operation Function of Major Components - 24
Cassette (Deck 1)
Paper Cassette
Cassette Sizing Assembly
Microswitches
Leaf Spring Actuator
Principles of Operation Function of Major Components - 25
Paper Transport (1 of 2)
Pickup Drive Assembly
The pickup drive assembly is responsible for mechanical drive to the cassette and manual
feed pickup rollers and to the cassette and preregistration feed rollers. It is powered by the
pickup motor. Contained within the assembly itself are the two feed rollers and the cassette
feed solenoid.
Main Drive Assembly
The main drive assembly is responsible for all mechanical drive from the registration
roller through paper delivery. It is powered by the main motor.
Drive Transfer Assembly
The drive transfer assembly is the gear train that transfers mechanical drive from the
main motor to the fuser assembly, delivery roller shaft, and photosensitive drum. An idler
gear is located along the path of the drive force transmission to the fuser. The idler gear
closes the path when the toner cartridge is installed
Registration Feed Roller
The registration feed roller, which is driven by the operation of the main drive assembly,
feeds paper in concert with the registration pinch roller. The pinch roller is spring-loaded
but passive. It receives no mechanical drive.
Registration Sensor/Actuator
The registration sensor is mounted to the power supply assembly. The registration actuator
is mounted to the frame. The sensor detects when paper reaches the registration position.
The signal of the registration sensor is used to position paper in synch with the toner image
on the drum.
Preregistration Sensor/Actuator
The preregistration sensor is mounted to the power supply assembly. The actuator is
mounted to the chute registration assembly. The preregistration sensor detects when paper
reaches the preregistration position.
Paper Deflector Solenoid
Switches the direction of the paper deflector guide.
Paper Deflector Guide
This guide is on the delivery side of the fuser. It controls whether paper passes into the
duplexer/face-up tray or outward onto the output tray.
Principles of Operation Function of Major Components - 26
Paper Transport (1 of 2)
Registration Pinch Roller
Main Drive Assembly
Registration Feed Roller
Paper Deflector Solenoid
Main Motor
Pickup Motor
Preregistration Feed Roller
Cassette Feed Roller
Pickup Drive Assembly
Cassette Feed Solenoid
Preregistration
Actuator A
Preregistration
Actuator B
Cassette Pickup Roller
Registration
Feed Roller
Paper Deflector Guide
Registration Actuator
Registration Sensor
Registration
Pressure Roller
Preregistration Pinch Roller
Preregistration Feed Roller
Cassette Pinch Roller
Cassette Feed Roller
Cassette Pickup Roller
Principles of Operation Function of Major Components - 27
Paper Transport (2 of 2)
Multipurpose Frame Assembly
The multipurpose frame assembly includes the manual feed solenoid, manual feed clutch
gear, manual feed pickup roller, separation pad, and the manual feed paper-present sensor
and actuator.
Principles of Operation Function of Major Components - 28
Paper Transport (2 of 2)
Manual Feed Solenoid
Manual Feed
Clutch Gear
Manual Feed Paper-Present
Actuator
Manual Feed Paper-Present
Sensor
Multipurpose Frame
Assembly
Manual Feed Pickup Roller
Separation Pad
Principles of Operation Function of Major Components - 29
Fusing and Paper Exit
Fuser Assembly
The major parts contained within the fuser assembly include the fuser heater bulb, fuser
roller, thermostat, fuse, and temperature sensor assembly.
The fuser heater bulb is located inside the fuser roller. Power to the bulb is switched on
and off so that the temperature of the fuser roller surface is kept constant. When the
temperature of the fuser rises to the predetermined upper limit temperature, the power
supply is switched off. This safeguard is known as first-stage overheat protection.
The fuser roller applies the heat for melting and fusing the toner to paper. It is connected to
the frame ground through a diode so that negative charge flows, thereby preventing the
toner image from being disturbed during the fusing process.
The thermostat is a part of the fuser bulb circuit and provides the second-stage overheat
protection. If the first-stage overheat protection fails to prevent overheat and the
thermostat reaches the predetermined temperature, the contacts of the thermostat open to
break the circuit between the fuser bulb and the power supply.
The fuse is also a part of the fuser bulb circuit and provides the third-stage overheat
protection. If the first and second stage protection both fail to prevent overheat and the fuse
reaches the predetermined temperature, the fuse melts to open the circuit between the
fuser and the power supply.
The temperature sensor is a resistor whose resistance varies rapidly with temperature. It
is positioned in contact with the surface of the fuser roller. Power to the fuser bulb is
switched on and off so that the temperature of the surface of the fuser roller is kept
constant.
Fuser Pressure Roller
The fuser pressure roller is a sponge roller covered with a tube. It is located beneath the
fuser assembly and is spring-loaded to apply pressure against the fuser roller as paper
passes. The fuser pressure roller is not mechanically driven.
Fuser Exit Sensor/Actuator
The fuser exit sensor is actuated as paper exits the fuser assembly but before paper reaches
the paper deflector guide.
Delivery Sensor/Actuators
The delivery sensor is actuated as paper reaches the delivery rollers.
Delivery Roller Shaft
The delivery roller shaft holds three fixed delivery rollers that feed paper through to the
output tray on the top of the printer.
Principles of Operation Function of Major Components - 30
Fusing and Paper Exit
Fuser Exit Actuator
Delivery Rollers
Fuser Assembly
Fuser Exit Sensor
Temperature
Sensor Assembly
Fuser Roller
Pressure Roller
Fuser Roller
Thermostat
Fuse
Heater Bulb
Fuser Exit
Pinch Roller
Pressure Roller
Fuser Exit Roller
Principles of Operation Function of Major Components - 31
Drive and Xerographic
For full description of the components in this section, see the “Print Image Creation” topic.
Laser/Scanner Assembly
The laser/scanner assembly includes the laser diode, scanner, lenses, and mirrors.
Note
: The laser/scanner assembly is a precision optical system. Never open the
cover. Touching the parts may result in permanent damage to the components.
Mirror Assembly
The mirror assembly includes the start-of-scan sensor (SOS) and the stationary mirror
that reflects the beam from the scanner mirror onto the photosensitive drum.
Toner Cartridge
The toner cartridge consists of a photosensitive drum and a toner container integrated into
one unit. It includes the following major components.
Photosensitive Drum
Bias Charge Roller (BCR)
Attraction Roller
Charging and Metering Blade (CMB)
Cleaning Blade
Laser Shutter
Transfer Roller
Principles of Operation Function of Major Components - 32
Drive and Xerographic (1 of 2).
Mirror Assembly
Toner Cartridge
Latch Shaft
Laser/Scanner Assembly
Spring
Lever Latch
Transfer Roller
Drum Shaft
Toner Cartridge
Flange
Toner Cartridge Latching Mechanism
Principles of Operation Function of Major Components - 33
Drive and Xerographic (2 of 2)
Start-of-Scan Sensor (SOS)
Laser Diode
Cylinder Lens
Hexagonal Mirror
Scanner Assembly
Collimator Lens
CM Blade
Lens L1
Bias Charge Roller
Mirror M1
Mirror Assembly
Laser/Scanner Assembly
Toner Cartridge
Shutter
Cleaning Blade
Attraction Roller
Photosensitive
Drum
Principles of Operation Function of Major Components - 34
Electrical
Power Supply Assembly
The power supply assembly is a large multifunctional circuit board located in the lower
section of the engine. Listed below are its major components.
Low-voltage power supply (LVPS): The LVPS generates stabilized DC voltages of 5 V,
12 V, and 24 V and supplies these voltages to the electrical components of the printer.
High-voltage power supply (HVPS): The HVPS generates AC and DC high voltages for
charge, development, transfer, and discharge in the print process. Those voltages are
supplied to the bias charge roller, attraction roller, transfer roller, and detack saw.
Interlock switch: This switch opens the supply circuits of 24 VDC and 5 VDC (+B) for
driving the laser diode.
Cassette paper-present sensor: This sensor is actuated by the cassette paper-present
actuator and detects when the cassette runs out of paper.
Power inlet: The power inlet is hard-wired directly to the circuit board.
DC Controller Board
The DC controller board controls the whole operation of the printer. Listed below are its
major functions:
Communication with the I/O board
Collection of the information from the sensors and switches.
Control of the laser/scanner assembly, fuser assembly, drive assemblies, and
solenoids.
Control of the print sequence.
Distribution of the low DC voltages to electrical components from the power supply
assembly.
Fan
The fan forces the air out of the printer to prevent overheating. There is only one fan in the
LaserWriter 12/640 PS.
Principles of Operation Function of Major Components - 35
Electrical
Registration
Sensor
Cassette Paper-
Present Sensor
I/O Controller Board
DC Controller Board
Power
Inlet
Power Supply
Assembly
Fan
Preregistration
Sensor
Interlock Switch
Principles of Operation Function of Major Components - 36
Frame
When the top cover closes, the seven events described below take place.
Cover Interlock Actuator
Top cover closure actuates the interlock switch on the power supply assembly. There are
three components that work together to actuate this switch.
Top cover actuator: The thin plastic post built into the top cover.
Spring-loaded actuator: The vertical assembly that transfers actuation downward.
Actuator arm: The arm that contacts the interlock switch on the power supply
assembly.
Laser Shutter
A plastic post built into the top cover extends through a cutout in the top of the laser/
scanner assembly. The laser shutter facing the mirror assembly opens, thus allowing the
laser beam to leave the laser/scanner assembly.
Mirror Assembly Shutter
A plastic post built into the top cover presses open the shutter that covers the mirror
assembly. Unless this shutter and the one above are in an open position, the laser can not
reach the photosensitive drum.
Cover Latch
Two latches on the chassis hook onto the underside of the cover to assure tight closure of the
cover. The right cover latch has an integral spring-loaded plate that is actuated by the top
cover release lever.
Jam Release Plate
The top cover presses against the surface of the jam release plate to the left of the laser/
scanner assembly. In a cover-closed position, this plate presses against the
preregistration pinch roller assembly, resulting in a tight gripping surface for paper feed.
In a cover-open condition, the pinch roller does not grip the paper, thus facilitating
removal of paper jams.
Toner Cartridge Latching Mechanism
Top cover closure actuates a cam mechanism that presses and stabilizes the toner cartridge.
See the “Drive and Xerographic (1 of 2)” illustration.
Fuser Idler Gear Actuation
There is a spring-loaded lever on the drive transfer assembly that controls the position of
the fuser idler gear. When the top cover is closed, this lever is pressed, thus completing
the drive train to the fuser assembly.
Principles of Operation Function of Major Components - 37
Frame
Fuser Idler
Gear Actuation
Jam Release Plate Laser
Shutter
Mirror Assembly
Shutter
Toner Cartridge
Latching Mechanism
Cover Interlock
Actuator
Cover
Latch
Interlock Switch
(on Power Supply Assy.)
Actuator Arm
Top Cover Actuator
(Spring-Loaded)
Principles of Operation Function of Major Components - 38
General Wiring Diagram
Fuser Assembly
14
J242
-2
P242
J242
To Duplexer or Sheet Feeder
P/J
232
-1
2
P/J
234-1
J2341
Cassette
Feed
Solenoid
Delivery
Sensor
P/J
285
33
Cassette Size
Sensing Assembly
Cassette Size
Microswitch
P/J234 P/J236
2
P/J
234-2
J2342
Manual
Feed
Solenoid
236-1
J236-2
236-3
Manual Feed
Paper-Present
Sensor
3
P/J
P/J
Fuser Exit
Sensor
P/J
281
P231
P/J
28
7
P/J
15
23
DC Controller
Thermistor
STS2 STS1
22
J292
P/J291
P/J29
P/J
26
21
Board
P/J
26
Fuser Heater
2
P/J11
Main
Switch
Cover
Interlock
Switch
Preregistration
Sensor
Registration
Sensor
Cassette Paper-
Present Sensor
Power Supply
Assembly
Laser/Scanner
Assembly
7
4
P/J
262
P/J
261
Laser
Diode
Scanner
Motor
N
L
Inlet
FG
P/J
222
P/J
221
Fan
Toner
Cartridge
(not used)
M
Pickup Motor
M
Main Motor
6
P/J
24
6
P/J
25
26
P/J
30
P/J
22
3
P/J
Start-of-Scan
301
3
Sensor
Paper Deflector
Solenoid
P/J 31
I/O Board
Principles of Operation Function of Major Components - 39
Ports
LocalTalk
Port
Ethernet Port
Communication Switch
Parallel Port
K
Service Source
Troubleshooting
LaserWriter 12/640 PS
Troubleshooting About the Status Panel - 1
About the Status Panel
The LaserWriter 12/640 PS has a status panel that consists of
three LEDs. The status reported through the LEDs is generated by
the I/O controller board based upon signals that the board receives
Ready
Paper
Out
Paper
Jam
from the printer sensing system and other engine monitoring
mechanisms. There are two types of reporting.
• End-user reporting consists of LED arrays that can be
observed by end users without need of special tools. This type of
reporting can be broken down into POST and PostScript
reporting (see following topics).
• Service technician reporting consists of LED arrays that can
only be observed through the use of a special tool. This
reporting is also referred to as EPOST (see topic later in this
chapter). Whereas end-user reporting can help you in
troubleshooting over the phone, EPOST requires that you be at
the printer location.
Troubleshooting POST (Power-On Self Test) - 2
POST (Power-On Self Test)
When you switch on power, all the status panel LEDs illuminate
briefly. This confirms that power is getting to the status panel and
that all LEDs are operational. All LEDs then extinguish and come
back on. This marks the start of POST.
POST is a set of diagnostic procedures that are written into
firmware on the I/O controller board. POST executes in the first
10 seconds of startup and checks the following three areas of the
printer in order:
• Stage 1 I/O controller (ROM & SIMMs)
• Stage 2 I/O controller (miscellaneous circuitry)
• Stage 3 D/C controller board
Troubleshooting POST (Power-On Self Test)/Stage Failure/POST - 3
Stage Failure/POST
POST extinguishes the LEDs from top to bottom as each test stage
passes. (The Ready LED is considered here to be the top LED). In a
POST Example
functional printer, the testing process takes about 40 seconds,
after which control passes to PostScript code in ROM and the
normal warm-up continues (see “PostScript Reporting” in this
chapter).
However, if POST detects a fault during any stage, the status panel
enters an error state and flashes the bottom two LEDs forever.
Making note of the stage from which this error array first
appears can help you choose the modules to bring on a service call.
For example, suppose failure occurs during stage two (only the
top LED had extinguished before the error array appears). This
indicates an I/O board failure, so a replacement board should
definitely accompany you on site.
Troubleshooting PostScript Reporting - 4
PostScript Reporting
PostScript reporting starts as soon as POST is completed. Most of
the time, PostScript will report according to the literal
designation of the LED. (For example, the paper-out LED
illuminates when the paper cassette is empty). However, there
are some instances where closer observation is critical in
interpreting the status panel.
• Solid ready light: In some cases, the ready light will illuminate
for as long as 15 seconds before a PostScript fault is reported.
Make sure to wait this extra time for PostScript to execute
before shutting down to perform further troubleshooting.
• Behavior before PostScript error: As with stage-reporting
during POST, it is sometimes necessary to note what occurs
before
following page notes where this is important.
the error array first appears. The chart on the
Troubleshooting PostScript Reporting/End-User Error Codes - 5
End-User Error Codes
Array
Description Explanation
Ready LED on
Ready LED flashes Printer is warming up or processing a job 1.
Paper-Out and
Paper-Jam LEDs
flash
All LEDs off
Paper-Out LED
illuminates
Paper-Jam LED
illuminates
Paper-Jam LED
flashes
Printer is ready
An error has been detected in POST. Observation
of LED behavior prior to this array can isolate the
fault to one of three general area (see "POST") 2.
The top cover is open.
No paper or cassette is not installed 3.
Paper is jammed in printer or toner cartridge
is missing 4.
Laser/scanner assembly error.
1
If the ready LED flashes forever, turn off the printer, disconnect it from the
network, and restart the printer. If the flashing does not recur, the problem
is most likely with networking or host computer software. If the flashing occurs
with a stand-alone printer, a faulty fan may be the problem.
2
If this array is preceded by the following behavior, the problem is likely with
the fuser assembly: ready LED comes on; ready LED flashes; fan comes on; and
paper for startup page is picked up but jams in the printer.
3
In some cases, this array can result from a faulty scanner motor or main motor.
4
For some residual paper jams (for example, where a jam exists in the delivery
area at time of startup), the printer may exhibit a ready state to the point where
the fan will come on and the paper for the startup page is picked up.
Troubleshooting EPOST (Extended Power-On Self Test) - 6
EPOST (Extended Power-On Self Test)
EPOST behaves exactly like POST in that it checks the same three
areas in the same order and displays an error array if a fault is
detected. However, EPOST has more extensive testing and its error
arrays are completely different. When a fault is detected during
EPOST, all LEDs extinguish and the status panel will loop through
the following sequence until you switch off power:
•
All LEDs On
•
All LEDs Off
•
EPOST Error Code
•
All LEDs Off
If no error is detected by EPOST, an EPOST test page will print
before control is passed on to the PostScript interpreter (if a
duplex unit is attached, two double-sided pages will print).
for approximately one second
for approximately one second
for approximately one second
for approximately two seconds, then repeat loop
Troubleshooting EPOST (Extended Power-On Self Test) - 7
Initiating EPOST
To initiate EPOST, you must have the printer rollback test plug
(P/N 922-1489). This test plug is colored bright green to
differentiate it from the older version black plug. Do not use the
black plug on the LaserWriter 12/640 PS. It won’t harm
anything; it just won’t work.
Switch off the printer and install the test plug into the LocalTalk
port on the back of the I/O controller board. Switch the printer
back on.
Troubleshooting EPOST (Extended Power-On Self Test) - 8
Stage Failure/EPOST
An EPOST error code can either illuminate solidly (for I/O
controller failures) or flash (for engine failures). The chart on
the next page shows the possible error arrays. The “EPOST
EPOST Example 1
EPOST Example 2
Example” animations demonstrate two of the combinations.
The “Example 1” animation simulates an I/O board error. Notice
how the EPOST announcement sequence (all LEDs on for a second
then all LEDs off for a second) is followed by a paper jam LED that
illuminates solidly for about a second.
The “Example 2” animation simulates a DC controller board
error. Notice how the EPOST announcement sequence is followed
by a paper jam LED that flashes for about a second.
Troubleshooting EPOST (Extended Power-On Self Test)/EPOST Error Codes - 9
EPOST Error Codes
All LEDs on for a second, then off for a second, followed by a
one-second display of...
...Solid Jam LED
= I/O Controller Board Error
...Solid Jam & Out LEDs
= ROM (I/O Controller) Error
...Solid Ready LED
= General SIMM Error
...Solid Ready & Jam LEDs
= SIMM (A/B) Error
...Solid Ready & Out LEDs
= SIMM (C/D) Error
FLASH
FLASH
FLASH
FLASH
FLASH
FLASH
FLASH
FLASH
FLASH
...Flashing Jam LED
= DC Controller Board Error
...Flashing Out LED
= Fuser Assembly Error
...Flashing Jam & Out LEDs
= Laser/Scanner Error
...Flashing Ready LED
= Fan Error
...Flashing Ready & Jam LEDs
= Miscellaneous Engine Error*
...Flashing Ready & Out LEDs
= Duplexer Error
FLASH
FLASH
FLASH
*
Miscellaneous engine error includes paper jams, top lid open, missing paper
cassette, no paper, or duplexer open.
...All Three LEDs Flashing
= Toner Cartridge Missing
Note: Always check for paper jams when a miscellaneous engine error occurs.
Many times paper is picked up to do a test print and an error occurs. When
you restart, the test will detect the paper jam first if the jam has not been
removed.
Troubleshooting Cleaning the Mirror - 10
Cleaning the Mirror
There is a small peach-colored square cleaner built into the
mirror assembly. Slide this square back and forth to remove
particles from the mirror.
Mirror
Cleaner
Troubleshooting Duplexer Jams - 11
Duplexer Jams
The paper guide provided with the duplexer
during setup. (Refer users to page 137 of the user manual). If you
must
be installed
Paper Guide
Troubleshooting Duplexer Jams - 12
fail to install this guide properly, jamming will frequently occur
as paper enters the duplexer from the printer. Be sure that the
two locking connectors are also fully snapped into place.
Locking Connectors
Troubleshooting Duplexer Jams - 13
If accordion-style jamming still occurs in the duplexer after
proper installation of the paper guide, replace the vertical
duplexer assembly (P/N 922-2001)
Troubleshooting Printing with 8.3 Driver/EPOST Error Codes - 14
Printing with 8.3 Driver
For purposes of troubleshooting paper feed, you can print with the
LaserWriter 8.3 driver from Mac OS computers. Simply copy the
PPD for the LaserWriter 12/640 PS into the Printer
Descriptions folder in the System Folder, select the printer
through the Chooser, and click on Setup.
You can print duplex jobs by clicking on the Options button in the
print dialog and making the appropriate selection. However, you
cannot print to the face-up tray with the 8.3 driver.
Note
: The LaserWriter 12/640 PS PPD is available on the June
1996 Service Source CD (path: Service Source:Service
Manuals:Clips).
Troubleshooting Out of Paper in Multipurpose Tray - 15
Out of Paper in Multipurpose Tray
If you are trying to print from the standard cassette and get an
error message saying that there is no paper in the multipurpose
tray, the problem may be in cassette setup.
There is a paper-length guide at the end of the cassette that must
be adjusted for letter size paper (the position as shipped is for A4
paper). When the AutoSelect feature built into PostScript
searches for letter size paper, the cassette will be passed over and
the controller assumes that the paper should be in the
multipurpose tray.
To rectify this situation, make sure that the length guide is
adjusted for letter size paper.
Troubleshooting Out of Paper in Multipurpose Tray/EPOST Error Codes - 16
.
Length Guide
in Letter Position
Troubleshooting Multipurpose Tray Paper Jams - 17
Multipurpose Tray Paper Jams
There have been a number of reported problems with the
multipurpose tray and its associated components. In the process of
resolving these problems, service providers may inadvertently
dislocate the solenoid flapper or actuator that is responsible for
releasing the multipurpose tray paper pickup roller so that it can
complete its paper pickup cycle. When this occurs the paper
pickup roller rotates constantly resulting in paper jams (if paper
is present) and annoying noises whenever the printer is being
used. Correcting the problem requires a service call.
Refer to the Multipurpose Tray Paper Jams pdf.
chapter for the repair procedure.
file in this
Troubleshooting False Paper Jam Error with Startup Page - 18
False Paper Jam Error with Startup Page
Symptom:
12/640 tries to print the startup page. No paper is picked up.
EPOST reports a DC Controller error. When the DC controller
board is replaced, the problem remains. Upon initiating a service
test print, the motor will spin for about a second and then will
stop with no test page output.
Discussion
the shield that covers the pickup drive assembly, and initiate a
service test print. You should see the pickup motor spin, and about
a second later see the solenoid trigger. If it does not, you either
have a bad solenoid, bad cassette size sensor board, or a bad cable
that runs between the solenoid and the sensor board. In the case of
the bad cassette size sensor board, it can cause EPOST to display a
DC controller error.
A false paper jam error occurs when the LaserWriter
: Observe the pickup solenoid through the small hole in
Troubleshooting Print Quality Problems - 1
Image Quality Problems
It can be easily determined whether an image quality problem is being caused by the print engine or by the
I/O controller board by producing a service test page. The service test page can be generated by jumpering the two pins of connector J101 on the I/O controller board.
If the test page is normal, but the regular prints have an image quality problem, the problem is probably
with the I/O controller board. If the test print has also the image quality problem, the problem is probably
in the print engine.
When troubleshooting an image problem, produce a test print using letter size or A4 paper, exactly identify the symptom, and isolate the problem by referencing the accompanying troubleshooting tables.
If the tables do not lead you to a solution to the problem, examine each part listed in the initial analysis of
the table corresponding to the problem. The fault is probably among those parts. Replace the part or parts
that in your judgment will most likely resolve the problem.
Roller Diameters
For a listing of the diameters of the rollers in the LaserWriter 12/640 PS, see page 13 in the Principles of
Operation chapter. Knowing these diameters can assist in troubleshooting repetitive horizontal print
defects.
List of Troubleshooting Tables
The troubleshooting tables cover the following typical fourteen image quality problems:
Table P-1 Light Prints
Table P-2 Blank Prints
Table P-3 Black Prints
Table P-4 Vertical Band Deletions
Table P-5 Horizontal Band Deletions
Table P-6 Vertical Streaks
Table P-7 Horizontal Streaks
Table P-8 Spot Deletions
Table P-9 Spots
Table P-10 Residual Image
Table P-11 Background
Table P-12 Skewed Image
Table P-13 Damaged Prints
Table P-14 Unfused Image
Table P-15 No PhotoGrade
Table P-16 No Duplex Printing
Table P-17 Duplex Page Upside-Down
Table P-18 No Multipurpose Tray Printing
Note : Vertical refers to the direction of paper travel. Horizontal refers to the direction perpendicular to
the direction of paper travel.
1
2
3
4
5
6
7
8
Troubleshooting Print Quality Problems - 2
P-1 Light Prints
Problem
The overall image density is lighter than normal.
Initial Analysis
Inspect the following components. Are they compatible with your printer version, correctly installed, not damaged, deformed or contaminated, or free of
foreign objects sticking?
• Toner Cartridge • Power Supply Assy • Transfer Roller Assy
• Mirror Assembly • Laser/Scanner Assy • DC Controller Board
• Fuser Assembly • Fuser Pressure Roller • Static Eliminator
• Top Cover
Step Actions and Questions
Paper conditions (moisture, warp, etc.)
Is the problem solved if you use new sheets of paper?
Toner cartridge
Is the problem solved by replacing the toner cartridge with a
new one?
Dirty reflecting mirror
Is the problem solved if you use the peach-colored slider
(built into the mirror assembly) to wipe the mirror clean?
Drum ground
Is the toner cartridge drum grounded securely?
* Check the drum ground path: drum > drum shaft pin >
Laser beam path
Are there obstructions or contamination on the laser beam
path from the laser/scanner assembly to the Drum?
Transfer roller assembly
Are there foreign objects or contamination on the roller
portion of the transfer roller assembly?
Charging and development
Is the toner image on the drum normally developed?
* Switch off the printer power while the development is in
progress, and visually check the toner image on the drum (the
area upstream of the transfer step).
Action
(When There Is Problem)
Replace the paper. Advise
the customer to stock paper
in a dry place.
Replace the toner cartridge.
Clean the mirror.
Restore the continuity of the
drum ground path.
Remove the obstructions or
contamination.
Replace the transfer roller
assembly.
Go to FIP-2.18 Power
Supply Assy (HV part)
failure.
Transfer
Is the toner image on the drum transferred normally on the
paper?
* Switch off the printer power while the transfer is in
progress, and visually check the toner image on the drum.
Go to FIP-2.18 Power
Supply Assy (HV part)
failure.
1
2
3
4
5
6
Troubleshooting Print Quality Problems - 3
P-2 Blank Prints
Problem
The entire print is blank.
Initial Analysis
Inspect the following components. Are they compatible with your printer version,
correctly installed, not damaged, deformed or contaminated, or free of foreign
objects sticking?
• Toner Cartridge • Power Supply Assy • Transfer Roller Assy
• Mirror Assembly • Laser/Scanner Assy • DC Controller Board
• Fuser Assembly • Fuser Pressure Roller • Static Eliminator
• Top Cover
Step Actions and Questions
Toner cartridge
Is the problem solved by replacing the toner cartridge with a
new one?
Drum ground
Is the toner cartridge drum grounded securely?
* Check the drum ground path: drum > drum shaft pin >
Laser beam path
Are there obstructions or contamination on the laser beam
path from the laser/scanner assembly to the Drum?
Transfer roller assembly
Are there foreign objects or contamination on the roller
portion of the transfer roller assembly?
Charging and development
Is the toner image on the drum normally developed?
* Switch off the printer power while the development is in
progress, and visually check the toner image on the drum (the
area upstream of the transfer step).
Transfer
Is the toner image on the drum transferred normally on the
paper?
* Switch off the printer power while the transfer is in
progress, and visually check the toner image on the drum.
Action
(When There Is Problem)
Replace the toner cartridge.
Restore the continuity of the
drum ground path.
Remove the obstructions or
contamination.
Replace the transfer roller
assembly.
Go to FIP-2.18 HV failure.
Go to FIP-2.18 Power
Supply Assy (HV part)
failure.
1
2
3
Troubleshooting Print Quality Problems - 4
P-3 Black Prints
Problem
The entire print is black.
Initial Analysis
Inspect the following components. Are they compatible with your printer version,
correctly installed, not damaged, deformed or contaminated, or free of foreign
objects sticking?
• Toner Cartridge • Power Supply Assy • Transfer Roller Assy
• Mirror Assembly • Laser/Scanner Assy • DC Controller Board
• Fuser Assembly • Fuser Pressure Roller • Static Eliminator
• Top Cover
Step Actions and Questions
Toner cartridge
Is the problem solved by replacing the toner cartridge with a
new one?
Charging
Use a sheet of paper to cover the window through which the
laser beam is emitted from the laser/scanner assembly.
Does the problem still occur?
Laser/scanner assy
Use a sheet of paper to cover half of the window through
which the laser beam is emitted from the laser/scanner
assembly.
Does the problem still occur?
Action
(When There Is Problem)
Replace the toner cartridge.
Replace power supply
assembly. If problem
persists, replace DC
controller board.
Replace laser/scanner
assembly. If problem
persists, replace DC
controller board.
1
2
3
4
5
6
7
7
Troubleshooting Print Quality Problems - 5
P-4 Vertical Band Deletions
Problem
There are areas of the image that are extremely light or missing entirely. These
missing areas form wide bands that run vertically along the page, in the direction
of paper travel.
Initial Analysis
Inspect the following components. Are they compatible with your printer version, correctly installed, not damaged, deformed or contaminated, or free of
foreign objects sticking?
• Toner Cartridge • Power Supply Assy • Transfer Roller Assy
• Mirror Assembly • Laser/Scanner Assy • DC Controller Board
• Fuser Assembly • Fuser Pressure Roller • Static Eliminator
• Top Cover
Step Actions and Questions
Dirty reflecting mirror
Is the problem solved if you use the peach-colored slider
(built into the mirror assembly) to wipe the mirror clean?
Paper conditions (moisture, warp, etc.)
Is the problem solved if you use new sheets of paper?
Toner cartridge
Is the problem solved by replacing the toner cartridge with a
new one?
Paper usability
If the problem still occurs after the toner cartridge is
replaced, again replace the toner cartridge with another new
one, and replace paper with standard paper.
Is the problem solved?
* When acid paper is used, this problem may occur because of
a component of paper.
Paper path
Are there obstructions such as burrs or objects or contami-
nation on the paper path?
Laser beam path
Are there obstructions or contamination on the laser beam
path from the laser/scanner assembly to the Drum?
Transfer roller assembly
Are there foreign objects or contamination on the roller
portion of the transfer roller assembly?
Fuser heater roller and fuser pressure roller
Are there scratches, contamination, or foreign objects on the
fuser heater roller or the fuser pressure roller?
Action
(When There Is Problem)
Clean the mirror.
Replace the paper. Advise
the customer to stock paper
in a dry place.
Replace the toner cartridge.
Replace paper with standard
paper.
Remove the obstructions or
replace the component.
Remove the obstructions or
contamination.
Replace the transfer roller
assembly.
Replace the roller.
1
2
3
4
5
6
7
Troubleshooting Print Quality Problems - 6
P-5 Horizontal Band Deletions
Problem
There are areas of the image that are extremely light or missing entirely. These
missing areas form wide bands that run horizontally across the page and parallel
with the direction of paper travel.
Initial Analysis
Inspect the following components. Are they compatible with your printer version, correctly installed, not damaged, deformed or contaminated, or free of
foreign objects sticking?
• Toner Cartridge • Power Supply Assy • Transfer Roller Assy
• Mirror Assembly • Laser/Scanner Assy • DC Controller Board
• Fuser Assembly • Fuser Pressure Roller • Static Eliminator
• Top Cover
Step Actions and Questions
Paper conditions (moisture, warp, etc.)
Is the problem solved if you use new sheets of paper?
Toner cartridge
Is the problem solved by replacing the toner cartridge with a new
one?
Charging and development
Is the toner image on the drum normally developed?
* Switch off the printer power while the development is in
progress, and visually check the toner image on the drum (the area
upstream of the transfer step).
Main drive assembly and drive transfer assembly
Does each gear of the drive assemblies rotate normally?
* Remove the fuser assembly and the toner cartridge. Rotate the
gear above at the rear of the drive assembly by hand in the rearward direction. Visually check the rotation of the gears.
Registration roller assembly
Does the registration roller assembly rotate normally?
* Open the cover and remove the toner cartridge. Rotate the
registration roller by hand.
Fuser assembly
Do the fuser heater roller and gears of the fuser assembly rotate
normally?
* Remove the fuser assembly. Rotate the fuser heater roller gear
by hand and check their rotation by eye.
Transfer roller assembly
Are there foreign objects or contamination on the roller portion of
the transfer roller assembly?
Action
(When There Is Problem)
Replace the paper. Advise
the customer to stock
paper in a dry place.
Replace the toner
cartridge.
Replace power supply
assembly. If problem
persists, replace DC
controller board.
Replace the drive
assembly.
Replace the registration
roller assembly.
Replace the fuser
assembly.
Replace the transfer
roller assembly.
8
9
Troubleshooting Print Quality Problems - 7
Step Actions and Questions
Transfer
Is the toner image on the drum transferred normally on the paper?
* Switch off the printer power while the transfer is in progress,
and visually check the toner image on the drum.
Fuser heater roller and fuser pressure roller
Are there scratches, contamination, or foreign objects on the
fuser heater roller or the fuser pressure roller?
Action
(When There Is Problem)
Replace power supply
assembly. If problem
persists, replace DC
controller board.
Replace the roller.
1
2
3
4
5
6
Troubleshooting Print Quality Problems - 8
P-6 Vertical Streaks
Problem
There are black lines running vertically along the page.
Initial Analysis
Inspect the following components. Are they compatible with your printer version,
correctly installed, not damaged, deformed or contaminated, or free of foreign
objects sticking?
• Toner Cartridge • Power Supply Assy • Transfer Roller Assy
• Mirror Assembly • Laser/Scanner Assy • DC Controller Board
• Fuser Assembly • Fuser Pressure Roller • Static Eliminator
• Top Cover
Step Actions and Questions
Toner cartridge
Is the problem solved by replacing the toner cartridge with a
new one?
Paper path
Are there obstructions such as burrs or objects or contami-
nation on the paper path?
Laser beam path
Are there obstructions or contamination on the laser beam
path from the laser/scanner assembly to the Drum?
Laser/scanner assy
Use a sheet of paper to cover the window through which the
laser beam is emitted from the laser/scanner assembly.
Does the problem still occur?
Transfer roller assembly
Are there foreign objects or contamination on the roller
portion of the transfer roller assembly?
Fuser heater roller and fuser pressure roller
Are there scratches, contamination, or foreign objects on the
fuser heater roller or the fuser pressure roller?
Action
(When There Is Problem)
Replace the toner cartridge.
Remove the obstructions or
replace the component.
Remove the obstructions or
contamination.
Replace laser/scanner
assembly. If problem
persists, replace DC
controller board.
Replace the transfer roller
assembly.
Replace the roller.
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