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Rebuild from Apple Service Guide for LaserWriter Printers Vol I (hosted) and the hosted LaserWriter II Service Course participant manual; every claim now cited. Corrected 11.5 MHz to Apple 11.16 MHz, 250-sheet cassette to 200, dimensions to 8.6x20x18.5 in., IIf 25 MHz to 20.0 MHz, SC font count. Removed unsourced price/dates/model number, 900 W / 7.5 A / 3,078 BTU, 48 dBA, engine life and duty cycle, first-page-out, 35-font list, 8-way DIP switch and interactive-PostScript/19200 baud claims,...
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{{Infobox computer peripheral
{{Infobox computer peripheral
| name        = Apple LaserWriter IINT
| name        = Apple LaserWriter II NT
| image        = [[File:Apple_LaserWriter_II.jpg|250px]]
| image        = [[File:Apple_LaserWriter_II.jpg|250px]]
| caption      = Apple LaserWriter IINT (1988)
| caption      = Apple LaserWriter II
| manufacturer = Apple Computer, Inc.
| manufacturer = Apple Computer, Inc.
| type        = Laser printer
| type        = Laser printer
| release date = January 1988
| interface    = LocalTalk / RS-422 (mini DIN-8); RS-232 (DB-25); Apple Desktop Bus connector present
| discontinued = October 1, 1991
| compatible  = Macintosh; other computers via RS-232
| price        = US$4,599 (1988 retail)
| dimensions  = 8.6 in. H x 20 in. W x 18.5 in. D
| interface    = LocalTalk, RS-232/RS-422 serial, ADB
| weight      = 45 lb (20.25 kg)
| compatible  = Macintosh, Apple II, PC (via RS-232)
| power        = 90-126 V AC, 50-60 Hz
| dimensions  = 8.7" H × 20.2" W × 18.7" D
| weight      = 45 lbs (20.4 kg)
| power        = 900W maximum, 90-126V/50-60Hz
| model        = M6000
}}
}}
<templatestyles src="Template:StyledTable/styles.css" />
The '''Apple LaserWriter II NT''' is the PostScript member of the LaserWriter II range. It shares the '''Canon LBP-SX''' engine, the case, the power supply and the entire mechanical parts list with the [[Apple LaserWriter II SC|II SC]] and the NTX; what makes it an NT is its controller-I/O board — a '''68000 at 11.16 MHz''' with '''1.0 MB of ROM''' and '''2.0 MB of RAM''', speaking '''PostScript''' and '''Diablo 630''' over LocalTalk, RS-232 and RS-422.<ref name="asg">''Apple Service Guide for LaserWriter Printers, Volume I'', Apple Computer, Inc., January 1992 (072-0631-B) — hosted on this wiki as [[:File:Apple LaserWriter Printers Volume I.pdf]]. Covers the LaserWriter, LaserWriter Plus, LaserWriter II SC/NT/NTX/IIf/IIg and Personal LaserWriter SC/NT/LS. Introductory safety section: the high-voltage, optical-fibre, fuser-cooling, ESD, not-being-grounded and lifting warnings; the LaserWriter Safety Rules; the toner-safety paragraph; the laser-safety paragraph and the three laser warning labels. Tab 3, LaserWriter II: parts list including the NT controller-I/O board and its ROM set (pages 4–5); controller-I/O board specifications (page 10); print engine specifications (page 11); status LEDs (page 12); test pages (page 13); the pre-power-on checklist, the troubleshooting flowcharts and tables including the NT low-toner note (pages 14–54); the laser power output check (page 55); and preventive maintenance including the page count, the parts replacement schedule and the user and standard maintenance tables (pages 59–60). Tab 6, Ports and Cables: the peripheral cable table, external connector diagrams, the RS-422 and RS-232 pin-outs and the LaserWriter II NT switch configuration table.</ref>


The '''Apple LaserWriter IINT''' was a midrange laser printer in the LaserWriter II series, released in January 1988 at US$4,599. The IINT positioned between the budget [[Apple LaserWriter II SC|IISC]] and high-end IINTX models, offering full PostScript Level 1 support and LocalTalk networking. The printer featured a Motorola 68000 processor running at 11.5 MHz with 2 MB of fixed RAM and 1 MB ROM containing 35 built-in fonts. Using the Canon LBP-SX print engine shared across the LaserWriter II line, the IINT delivered 300 dpi resolution at 8 pages per minute. Performance improvements over earlier models came from elimination of memory wait states, providing faster PostScript rasterization. The IINT was discontinued in October 1991, replaced by the LaserWriter IIf.
'''Before you take the covers off, read the [[#Safety|Safety]] section.''' There is an '''invisible''' laser inside, a fuser that needs five minutes to cool, and a high-voltage supply for the coronas.


== Technical Specifications ==
== Controller-I/O Board ==


=== Physical Specifications ===
Apple's table for the whole range, which is the clearest single comparison available:<ref name="asg" />
* '''Dimensions:''' 8.7" H × 20.2" W × 18.7" D (221 × 513 × 475 mm)
* '''Weight:''' 45 lbs (20.4 kg)
* '''Operating temperature:''' 50°F to 90°F (10°C to 32°C)
* '''Humidity:''' 20% to 80% non-condensing
* '''Acoustic noise:''' 48 dBA operating


=== Performance ===
{| class="wikitable styled-table" style="width:95%;"
* '''Print speed:''' 8 pages per minute
|+'''Controller-I/O board specifications'''<ref name="asg" />
* '''Resolution:''' 300 × 300 dpi
! !! SC !! '''NT''' !! NTX !! IIf !! IIg
* '''First page out:''' Approximately 30 seconds
|-
* '''Engine life:''' 300,000 pages rated
| '''CPU''' || 68000 (7.45 MHz) || '''68000 (11.16 MHz)''' || 68020 (16.67 MHz) || 68030 '''(20.0 MHz)''' || 68030 (25.0 MHz)
* '''Duty cycle:''' 3,000 pages per month recommended
|-
| '''ROM''' || 16 KB || '''1.0 MB''' || 1.0 MB || 2.0 MB || 2.0 MB
|-
| '''RAM''' || 1.0 MB || '''2.0 MB''' || 2.0 MB, expandable to 12 MB || 2.0 MB, expandable to 32 MB || 5.0 MB, expandable to 32 MB
|-
| '''I/O''' || SCSI || '''LocalTalk, RS-232, RS-422''' || LocalTalk, RS-232, RS-422, SCSI || LocalTalk, RS-232, RS-422, SCSI || LocalTalk, RS-232, RS-422, SCSI, Ethernet
|-
| '''Imaging languages''' || QuickDraw || '''PostScript, Diablo 630''' || PostScript, Diablo 630, HP LaserJet || PostScript Level 1 & 2, HP LaserJet IIP || PostScript Level 1 & 2, HP LaserJet IIP
|-
| '''Built-in fonts''' || Times, Helvetica, Courier, Symbol || '''Times, Courier, Symbol, Palatino, Helvetica, Helvetica Narrow, ITC Bookman, ITC Avant Garde, ITC Zapf Chancery, New Century Schoolbook, ITC Zapf Dingbats''' || as NT || as NT || as NT
|}


=== Power Requirements ===
Three things in that table are commonly misreported. '''The NT runs at 11.16 MHz''', not 11.5. '''The IIf runs at 20.0 MHz''', not 25.0 — the IIg is the 25 MHz machine. And Apple's guide '''gives eleven font families, not a font count'''; the familiar "35 fonts" figure is a count of individual styles that Apple's service documentation does not state, so it is not given here.
* '''Input voltage:''' 90-126V AC (auto-ranging)
* '''Frequency:''' 50-60 Hz
* '''Power consumption:''' 900W maximum
* '''Current draw:''' 7.5A maximum
* '''Heat output:''' 3,078 BTU per hour


== System Architecture ==
'''The NT's 2.0 MB is not expandable.''' Apple documents memory upgrades for the NTX and for the IIf/IIg only; there is no NT memory upgrade in the guide.<ref name="asg" />


=== Processor and Memory ===
=== Board layout ===
The LaserWriter IINT used an optimized 68000 configuration:


'''Central Processing Unit:'''
Apple's service course diagram of the NT controller-I/O board shows an '''MC68000''', a '''6532 VIA''', an '''8530 SCC''', '''1 MB of ROM''', '''2 MB of RAM''' and a bank of SRAMs, with the Apple Desktop Bus connector, a '''two-position switch''', the RS-232 port and the LocalTalk/RS-422 port along the back panel. The board mates with the print engine through a '''32-pin right-angle connector''' that engages as the board slides into the guide rails in the base of the engine.<ref name="train">''Apple Service Training: LaserWriter II Service Course, Participant Manual, Version 1.1'', Apple Computer, Inc., October 1992 — hosted on this wiki as [[:File:Apple LaserWriter II Service Training Participant Manual Version 1.1 Oct 1992.pdf]]. Module 1, "LaserWriter II Parts and Functions": the SC, NT and NTX I/O board block diagrams and back panels (figures 1-3 to 1-5) and the 32-pin right-angle engine connector; the four-subsystem breakdown (power distribution, control, image formation, pickup/feed); the power distribution diagram (figure 1-7); the DC controller PCB's role; the interlock switch at the top of the DC power supply; the status panel description; the distribution PCA (figure 1-12) with drum-sensitivity switches SW301 and SW302, pickup solenoid SL301, registration clutch solenoid SL302, paper-out sensor PS301 and manual feed sensor PS302; and paper delivery sensor PS331 on the fuser PCA.</ref>
* '''CPU:''' Motorola MC68000
 
* '''Clock speed:''' 12 MHz crystal (operating at 11.5 MHz)
=== Board and ROM part numbers ===
* '''Data bus:''' 16-bit
 
* '''Address bus:''' 24-bit (16 MB addressable)
{| class="wikitable styled-table" style="width:70%;"
* '''Wait states:''' None (improved from LaserWriter Plus)
|+'''NT controller-I/O board'''<ref name="asg" />
! Part !! Number
|-
| Controller-I/O Board, LW II NT || '''661-0438'''
|-
| IC, ROM, L0 || 342-0545
|-
| IC, ROM, H0 || 342-0546
|-
| IC, ROM, L1 || 342-0547
|-
| IC, ROM, H1 || 342-0548
|-
| IC, ROM, L2 || 342-0549
|-
| IC, ROM, H2 || 342-0550
|-
| IC, ROM, L3 || 342-0551
|-
| IC, ROM, H3 || 342-0552
|}
 
'''Eight ROMs in high/low pairs, L0/H0 through L3/H3.''' A board with a different ROM complement is not an NT board: the NTX takes eight differently numbered ROMs (342-0560 to 342-0567, or 342-0711 to 342-0718 on the rev 3 board), and the IIf and IIg take four (076-0860 to 076-0863).<ref name="asg" />
 
== Ports and Switches ==
 
The NT's rear panel carries, left to right, an '''Apple Desktop Bus connector''', a '''switch bank''', the '''RS-232''' port and the '''LocalTalk/RS-422''' port.<ref name="asg" />
 
The ADB connector is present on the SC, NT and NTX and was '''removed on the IIf and IIg''', which use a pushbutton switch instead.<ref name="asg" /> Apple's guide documents its presence but describes no function for it, so none is claimed here.
 
{| class="wikitable styled-table" style="width:70%;"
|+'''RS-422 / LocalTalk — mini DIN-8 male''' (shared with the NTX, IIf, IIg and Personal LaserWriter NT)<ref name="asg" />
! Pin !! Signal !! Description
|-
| 1 || HSKo || Handshake out
|-
| 2 || HSKi || Handshake in
|-
| 3 || TxD− || Transmit data −
|-
| 4 || SG || Signal ground
|-
| 5 || RxD− || Receive data −
|-
| 6 || TxD+ || Transmit data +
|-
| 7 || GPi || General-purpose input
|-
| 8 || RxD+ || Receive data +
|}


'''Memory Configuration:'''
{| class="wikitable styled-table" style="width:70%;"
* '''ROM:''' 1 MB mask ROM
|+'''RS-232 — DB-25 male'''<ref name="asg" />
* '''RAM:''' 2 MB total (fixed, soldered to board)
! Pin !! Signal !! Description
** PostScript workspace and font cache
|-
** Frame buffer for page rasterization
| 1 || SGND || Signal ground
|-
| 2 || TxD || Transmitted data
|-
| 3 || RxD || Received data
|-
| 4 || RTS || Request to send
|-
| 5 || CTS || Clear to send
|-
| 6 || DSR || Data set ready
|-
| 7 || SG || Signal ground
|-
| 8 || DCD || Data carrier detect
|-
| 20 || DTR || Data terminal ready
|-
| 22 || RI || Ring indicator
|}


* '''RAM type:''' Fast DRAM (no wait states)
=== Switch configurations ===
* '''Memory expansion:''' None possible
* '''Performance:''' Faster rasterization than LaserWriter Plus


=== Controller Board Design ===
'''The NT has two switches, not a bank of eight.''' Apple's table is short enough to memorise, and a printer that will not talk to anything is very often simply set to the wrong one:<ref name="asg" />
The IINT controller featured improved architecture:


* '''PostScript interpreter:''' Level 1 implementation
{| class="wikitable styled-table" style="width:70%;"
* '''Font management:''' 35 fonts in ROM
|+'''LaserWriter II NT switch configurations'''<ref name="asg" />
* '''Graphics processing:''' Vector and bitmap support
! Communication and command mode !! 1 !! 2
* '''Interface logic:''' PAL-based design
|-
* '''Memory controller:''' Zero wait-state access
| LocalTalk || Up || Up
|-
| Diablo 630 emulation || Down || Up
|-
| 9600 baud RS-232 & RS-422 || Up || Down
|-
| 1200 baud RS-232 & RS-422 || Down || Down
|}


=== PostScript Implementation ===
'''Those are the only two serial rates the NT offers.''' The NTX adds a six-switch bank with separate command-mode and handshaking groups, including a PostScript interactive mode and an HP LaserJet mode; '''the NT has neither'''.<ref name="asg" />
'''PostScript Specifications:'''
* '''Version:''' PostScript Level 1
* '''Licensor:''' Adobe Systems
* '''Language features:''' Complete programming language
* '''Graphics:''' Vector graphics, Bézier curves, transformations
* '''Font handling:''' Type 1 and Type 3 support
* '''Emulation:''' Diablo 630 mode available


'''Performance Improvements:'''
Apple's cable for the NT is the '''LocalTalk Connector Kit, DIN-8''', service part 590-0338 or 630-8275, Apple model '''M2068''' — the same kit used by the NTX, IIf, IIg and Personal LaserWriter NT.<ref name="asg" />
* Eliminated wait states from LaserWriter Plus
* Faster font cache management
* Improved complex page handling
* Reduced processing time for graphics


== Print Engine ==
== Print Engine ==


=== Canon LBP-SX Engine ===
{| class="wikitable styled-table" style="width:90%;"
The IINT used the improved Canon LBP-SX engine:
|+'''LaserWriter II print engine specifications'''<ref name="asg" />
| '''Marking engine''' || Canon LBP-SX laser xerographic
|-
| '''Print resolution''' || 300 dots per inch
|-
| '''Speed''' || 8 pages per minute
|-
| '''Print materials''' || Letter, legal, A4 and B5 sizes use '''16–20 lb''' single-sheet photocopy bond, '''8–34 lb''' letterhead and coloured stock, or transparency overhead film. Envelopes, labels and paper up to '''36 lb''' via manual feed; envelopes also via an optional envelope tray
|-
| '''Print capacities''' || '''Paper cassettes hold 200 sheets of 20-lb paper. Envelope cassette holds 15 envelopes'''
|-
| '''Printable surface''' || Letter 8.0 × 10.5 in.; Legal 8.0 × 13.0 in.; A4 7.41 × 10.86 in.; B5 7.69 × 10.16 in.
|-
| '''Physical dimensions''' || Height '''8.6 in. (21.8 cm)'''; width '''20 in. (50.8 cm)'''; depth '''18.5 in. (47 cm)'''; weight '''45 lb (20.25 kg)'''
|-
| '''Operating environment''' || 50 to 90 °F (10 to 32.5 °C); humidity 20% to 80%
|-
| '''Power requirements''' || '''90 to 126 volts AC; 50 to 60 Hz'''
|}


'''Engine Specifications:'''
'''The cassette holds 200 sheets, not 250.''' Apple's guide gives '''no''' wattage, current draw, BTU figure, acoustic noise level, rated engine life, monthly duty cycle or first-page-out time for the LaserWriter II, and none is stated here.
* '''Technology:''' Laser xerography (electrophotographic)
* '''Photosensitive drum:''' Organic photoconductor (OPC)
* '''Laser type:''' Semiconductor laser diode
* '''Developer system:''' Single-component toner
* '''Fusing:''' Heat roller system
* '''Paper path:''' Straight-through design


'''Advantages over LBP-CX:'''
=== The four subsystems ===
* 32% weight reduction
* Improved reliability
* Quieter operation
* Better paper handling
* Longer component life


=== Consumables ===
Apple's service course splits the engine into four, and the split is the fastest way to localise a fault:<ref name="train" />
* '''Toner cartridge:''' Apple M6002 or HP 92295A
* '''Yield:''' Approximately 4,000 pages at 5% coverage
* '''Drum life:''' Integrated with toner cartridge
* '''Paper tray:''' 250-sheet capacity letter/legal cassette
* '''Manual feed:''' Single-sheet bypass for special media


== ROM Fonts ==
* '''Power distribution''' — the AC inlet and power switch, the AC driver board and fuser heater, the DC power supply/motor driver PCA, the high-voltage power supply feeding the primary corona, transfer corona and developing bias, and the distribution PCA.
* '''Control''' — the '''DC controller PCB''', which receives the print command from the controller-I/O board, drives everything else and reports engine status on the front-panel LEDs. Apple's advice is explicit: always check the DC controller as part of troubleshooting, because a module that looks faulty may simply never have received its command or its supply.
* '''Image formation''' — laser diode, scanning motor and optical fibre, photosensitive drum, coronas, static-charge eliminator, toner sensor and fuser.
* '''Pickup/feed''' — cassette, pickup and registration rollers, their solenoids and the paper sensors.


The LaserWriter IINT included 35 built-in PostScript Type 1 fonts (same as LaserWriter Plus):
=== Sensors, switches and solenoids ===


=== Core Font Families ===
Real designators, for probing rather than guessing:<ref name="train" />


'''Times''' (4 styles):
{| class="wikitable styled-table" style="width:85%;"
* Times-Roman
! Designator !! Where !! What it does
* Times-Italic
|-
* Times-Bold
| '''PS301''' || Distribution PCA || Paper-out sensor — senses paper in the cassette
* Times-BoldItalic
|-
| '''PS302''' || Distribution PCA || Manual feed sensor — '''shares its arm with PS301'''
|-
| '''PS331''' || Fuser PCA / fuser assembly PCA || Paper delivery sensor. Paper that fails to reach and clear it in time '''is''' the jam
|-
| '''SL301''' || Distribution PCA || Pickup roller solenoid — engages the clutch that turns the pickup roller
|-
| '''SL302''' || Distribution PCA || Registration roller clutch solenoid — feeds paper towards the drum
|-
| '''SW301, SW302''' || Distribution PCA || Drum-sensitivity switches, read from the cams on the toner cartridge so the DC controller can match laser intensity to the drum
|-
| Interlock switch || Top of the DC power supply || Cuts power when the upper unit opens; the interlock lever presses it when the unit closes
|}


'''Helvetica''' (8 styles):
Two of those explain faults that are otherwise baffling. '''PS301 and PS302 share one arm''', so a bent or sticking arm can produce a paper-out indication and a manual-feed fault at once. And a jam reported with no paper in the machine is normally '''PS331''' or its timing, not the paper path.
* Helvetica
* Helvetica-Oblique
* Helvetica-Bold
* Helvetica-BoldOblique
* Helvetica-Narrow
* Helvetica-Narrow-Oblique
* Helvetica-Narrow-Bold
* Helvetica-Narrow-BoldOblique


'''Courier''' (4 styles):
== Safety ==
* Courier
* Courier-Oblique
* Courier-Bold
* Courier-BoldOblique


=== Display Fonts ===
The LaserWriter family safety rules apply in full:<ref name="asg" />


'''ITC Avant Garde Gothic''' (4 styles):
* '''High voltage.''' Switch off and disconnect the AC power cord before servicing. Certain parts are electrified under power. Never work on the printer under power '''except when making live adjustments'''.
* AvantGarde-Book
* '''Laser.''' '''Do not disconnect the optical fibre cable when the printer is powered on.''' The fibre carries the infrared laser beam, '''which you cannot see but which can permanently damage your eyes'''. When servicing the optical system, do not put screwdrivers or other shiny objects in the beam path — the reflected beam is equally dangerous. Apple's own warning labels inside the covers read "DANGER — INVISIBLE LASER RADIATION WHEN OPEN. AVOID DIRECT EXPOSURE TO BEAM."
* AvantGarde-BookOblique
* '''Fuser.''' The fuser rollers become very hot. '''Switch off for at least five minutes''' before servicing them.
* AvantGarde-Demi
* '''Do not touch''', with covers off and power on: the high-voltage power supply, the DC power supply, or '''the power supply block''', which is the LaserWriter II-specific item on Apple's list.
* AvantGarde-DemiOblique
* '''Do not be grounded''' when working on plugged-in equipment or making live adjustments, and '''remove all jewellery before you start'''.
* '''ESD.''' The controller-I/O board contains CMOS parts, and CMOS chips, ROMs and SIMMs are very susceptible to electrostatic discharge and skin acid. '''Handle them by the edges only.'''
* '''Weight.''' 45 lb. Apple warns about lifting LaserWriters for good reason.
* '''Toner''' is non-toxic — plastic, iron and a little pigment. Remove as much as possible with a dry tissue, then wash with '''cold''' water; hot water gels it and fuses it permanently into fabric. '''Toner attacks vinyl.'''
* '''Never use an ammonia-based cleaner on the LaserWriter II''' — it discolours the plastic.


'''ITC Bookman''' (4 styles):
== Status LEDs ==
* Bookman-Light
* Bookman-LightItalic
* Bookman-Demi
* Bookman-DemiItalic


'''New Century Schoolbook''' (4 styles):
'''There are four, all on the front panel, and none of them is a "Service" light.'''<ref name="asg" /><ref name="train" />
* NewCenturySchlbk-Roman
* NewCenturySchlbk-Italic
* NewCenturySchlbk-Bold
* NewCenturySchlbk-BoldItalic


'''Palatino''' (4 styles):
{| class="wikitable styled-table" style="width:92%;"
* Palatino-Roman
|+'''LaserWriter II status LEDs'''<ref name="asg" />
* Palatino-Italic
! LED !! Colour !! Behaviour
* Palatino-Bold
|-
* Palatino-BoldItalic
| '''Ready''' || Green || Flashes during warm-up and while the printer is operating. Steady when warmed up and ready. '''Off''' when the printer is not ready, an error condition exists, or the top cover is open
|-
| '''Low-Toner''' || '''Orange''' || On and steady when the toner cartridge needs replacement. '''Flashes when the cartridge is installed incorrectly'''
|-
| '''Paper-Out''' || '''Red''' || On and steady when out of paper or the paper tray is missing. '''Flashes when the printer is ready to accept manually fed paper'''
|-
| '''Paper Jam''' || Red || Comes on when paper jams and stays on until the jam is cleared
|}


=== Specialty Fonts ===
'''The error indication is a combination, not a light of its own:'''<ref name="asg" />


* '''Symbol:''' Mathematical and Greek characters
> When both the red '''Paper-Out''' and '''Paper Jam''' lights flash, the controller-I/O board or the print engine has an error condition.
* '''ZapfChancery-MediumItalic:''' Decorative script
* '''ZapfDingbats:''' Ornaments and symbols


== Interfaces ==
=== Things that are not faults ===


=== LocalTalk Interface ===
* '''A new toner cartridge that leaves the Low-Toner LED on.''' Apple documents this for the NT specifically: after a new cartridge goes in, the Low-Toner LED '''stays lit until the printer produces a printout, or until you switch it off and on again'''.<ref name="asg" />
Primary networking interface for AppleTalk:
* '''A flashing Low-Toner LED''' means the cartridge is seated wrongly, not that it is empty.
* '''A flashing Paper-Out LED''' means the printer is waiting for you to hand-feed a sheet.
* '''The Ready LED going off''' is how the printer reports trouble — there is no separate service lamp to look for.


'''LocalTalk Specifications:'''
== Test Pages ==
* '''Physical layer:''' RS-422 differential signaling
* '''Data rate:''' 230.4 kbps
* '''Topology:''' Bus with daisy-chaining
* '''Maximum nodes:''' 32 devices theoretical (16 practical)
* '''Protocol:''' AppleTalk protocol stack
* '''Connector:''' Mini-DIN-8


'''LocalTalk Features:'''
Two pages, testing the two halves of the machine. Knowing which is which halves the diagnostic problem immediately.<ref name="asg" />
* Automatic node addressing
* Collision detection and avoidance
* Network printer sharing
* Compatible with PhoneNET adapters


=== Serial Interfaces ===
=== Engine self-test page — tests the print engine ===
The IINT provided dual serial connectivity:
'''Press the engine self-test switch, located on the side of the printer behind the access cover.'''<ref name="asg" /> This runs the '''print engine alone''' — no computer, no network, no driver — and is how you isolate engine failures from controller-I/O board failures.


'''RS-232 Interface:'''
=== Startup test page — tests the controller-I/O board ===
* '''Connector:''' DB-25 female
The NT generates a startup test page '''every time it is switched on''', unless the user has switched the function off with PostScript software or with the LaserWriter Utility on the LaserWriter II Installation disk.<ref name="asg" /> It confirms the controller-I/O board and carries the page count.
* '''Data rate:''' Up to 19,200 baud
* '''Data format:''' 8 bits, no parity, 1 stop bit
* '''Flow control:''' XON/XOFF or hardware (RTS/CTS)
* '''Usage:''' PC connectivity, terminal access


'''RS-422 Interface:'''
'''So: a fault on the engine self-test page is in the engine. A machine that prints a clean engine self-test but no startup test page has a controller-I/O board fault. A machine that passes both but will not print from the Macintosh has a cable, switch-setting, driver or host problem''' — and on an NT, check the two-position switch before anything else.
* '''Connector:''' Mini-DIN-8 (shared with LocalTalk)
* '''Data rate:''' Up to 57,600 baud
* '''Protocol:''' AppleTalk or serial
* '''Cable length:''' Up to 1200 feet


'''Switch-Selectable Modes:'''
== Troubleshooting ==
* LocalTalk (default)
* RS-232 serial
* RS-422 serial
* Diablo 630 emulation


=== ADB Port ===
=== Pre-power-on checklist ===
Like the IISC, the IINT included an unused ADB port:
Apple's list, to be worked through before the flowcharts:<ref name="asg" />


* '''Connector:''' 4-pin mini-DIN
* Line voltage is OK — '''115 volts AC ±10%'''
* '''Purpose:''' Reserved for future expansion
* Printer is on a solid, level surface
* '''Implementation:''' Non-functional
* Room temperature '''50–90 °F (10–32.5 °C)''', humidity 20%–80%
* '''Removed:''' Eliminated in IIf and IIg models
* Not in a hot, humid or dusty area, nor near open flames
* '''Printer is not exposed to ammonia gas'''
* Not in direct sunlight; well ventilated
* Cables and connectors are OK
* Toner cartridge installed and has toner
* '''Fuser roller cleaner felt is in place and not dirty'''
* Print density adjustment dial set correctly
* Paper cassette properly loaded and paper within specification
* '''Transfer corona wire clean and unbroken'''
* '''I/O PCA DIP switches are set correctly'''


=== Interactive PostScript ===
The ammonia item is not a curiosity — diazo copiers and some cleaning products produce it, and it will degrade the machine.
Accessible via RS-232 for direct control:


'''Terminal Access:'''
=== Troubleshooting order ===
* Connect terminal to RS-232 port
Apple's sequence is fixed: check the pre-power-on list; be familiar with the safety section before any live electrical check; '''for an SC or NT/NTX begin with Troubleshooting Flowchart 1''' and proceed function by function until every main function is verified; '''if you replace a module and the problem remains, reinstall the original before proceeding'''; and perform preventive maintenance before returning the printer.<ref name="asg" />
* Settings: 19,200 baud, 8-N-1
* Type "executive" to enter interactive mode
* Direct PostScript programming possible
* Diagnostic information available


== Paper Handling ==
'''The IIf/IIg status-LED diagnostic does not apply to the NT.''' That procedure — rear rotary switch to 4, LaserWriter II Test Connector on the DB-25 port, read the LEDs against a table — exists only on the IIf and IIg.<ref name="asg" />


=== Input Specifications ===
=== Laser power output check ===
* '''Standard cassette:''' 250 sheets
Apple's procedure, which needs a laser power checker and a digital multimeter. '''The check figure is 17.6 mV ± 1.6 mV.'''<ref name="asg" />
* '''Manual feed:''' Single sheets
* '''Paper sizes:''' Letter, Legal, A4, Executive, B5
* '''Paper weight:''' 16-28 lb bond (60-105 g/m²)
* '''Media types:''' Plain paper, transparencies, envelopes, labels


=== Output Specifications ===
# Put the printer on a grounded workbench pad and remove the controller-I/O board and the cover set.
* '''Output tray:''' 250-sheet capacity face-down
# '''With the power off''', open the laser access hatch on the laser/scanner assembly.
* '''Page order:''' First page on bottom
# Insert the laser power checker into the hatch with the detector facing the laser diode.
* '''Duplex:''' Manual duplex only
# Black lead to the meter's "Common" socket, red lead to "Volts"; set the meter to volts, '''200 mV range'''.
* '''Maximum monthly volume:''' 3,000 pages
# Defeat the top cover interlock switch with a '''nonmetallic''' tool, switch on and wait one minute for warm-up.
# Depress drum-sensitivity switches '''SW301 and SW302''' below the top cover interlock switch, and press the service test print button.
# Read the meter. '''17.6 mV ± 1.6 mV.'''


== Diagnostic Features ==
If the power cannot be measured at all, Apple's order is to replace the '''laser/scanner assembly''' and repeat, and if it still cannot be measured, the '''DC controller PCA'''.<ref name="asg" /> Note that this procedure defeats the cover interlock deliberately: the laser is running with the covers off, and the safety rules above apply at their strictest.


=== Self-Test Page ===
== Preventive Maintenance ==
The IINT printed a comprehensive test page showing:
* Printer model and serial number
* ROM version
* Installed RAM (2 MB)
* Page count
* Font samples (all 35 fonts)
* PostScript version
* Configuration settings


=== Status Indicators ===
=== Before starting ===
Front panel LED indicators:
Power off and unplug; '''let the fuser assembly rollers cool'''; prepare the work area for ESD; spread a drop cloth against grease and spilled toner.<ref name="asg" />
* '''Ready (green):''' Solid when ready
* '''Data (green):''' Flashing during data reception
* '''Paper (amber):''' Paper out or jam
* '''Service (red):''' Service required


=== Service Button ===
=== Page count ===
DC controller board service button:
Switch on and wait for the startup test page. The number at the bottom is the pages printed '''since the controller-I/O board was installed''' — accurate only if that board has never been repaired or upgraded. If it has, Apple's instruction is to check the '''Repair Log Label on the bottom of the printer''' and ask the customer.<ref name="asg" />
* Single press: Print test page
* Hold during power-on: Continuous test mode


== Common Issues and Maintenance ==
=== Apple's parts replacement schedule ===
'''Every 50,000 prints:''' replace the '''ozone filter''' and check the fan.<ref name="asg" />


=== Known Problems ===
'''Every 100,000 prints,''' replace:<ref name="asg" />
* Fuser assembly
* Transfer guide assembly
* Preconditioning exposure assembly
* Paper feed roller assembly
* Transfer corona assembly


{| class="wikitable" style="width:90%; text-align:center;"
'''That is the whole schedule.''' Apple's guide has no monthly, annual-by-page-count or 200,000/300,000-print item for this machine, and the ozone filter — a genuine consumable that is very often never changed — is the one most worth acting on.
|+'''Common IINT Failures'''
 
! Component !! Symptoms !! Cause !! Repair
=== Cleaning ===
{| class="wikitable styled-table" style="width:80%;"
|+'''Service points and what to use'''<ref name="asg" />
! Service point !! Tool or solvent
|-
|-
| DC controller || No power, random resets || Capacitor failure || Recap board
| Primary corona wire || Cleaning brush supplied with the printer
|-
|-
| Logic board || PostScript errors || RAM failure || Replace RAM (requires desoldering)
| Transfer corona wire || Cotton swab (with isopropyl alcohol, for user cleaning)
|-
|-
| Power supply || Voltage instability || Aged capacitors || Replace all electrolytics
| Transfer guide || Cloth dampened with water
|-
|-
| Fuser assembly || Poor adhesion, wrinkled pages || Worn roller || Replace fuser unit
| Fuser rollers || Fuser cleaning pad
|-
|-
| Corona wires || Light print, streaking || Contamination || Clean or replace
| Exterior case || Cloth dampened with water
|-
|-
| Paper feed || Multiple feeds, jams || Worn rollers || Clean/replace rollers
| Separation claws || Cloth dampened with alcohol
|-
| Paper guide || Cloth dampened with alcohol
|-
| Lower delivery guide || Cloth dampened with alcohol
|-
| Feeder guide || Cloth dampened with water
|-
| Registration rollers || Cloth dampened with water
|}
|}


=== Capacitor Issues ===
Apple splits these into items the customer cleans as needed (the first five) and a dealer list to be done '''every 12 months or at each service call''' (all ten).<ref name="asg" /> Note which points take water and which take alcohol — they are not interchangeable.
The IINT logic board was prone to capacitor failure:
* Surface-mount capacitors leak over time
* Causes intermittent operation or failure
* All capacitors should be replaced preventively
* Use 105°C rated replacements


=== Preventive Maintenance ===
== Parts ==


'''Service Intervals:'''
Selected entries, common to the LaserWriter II range except where the NT is named:<ref name="asg" />
* '''Monthly:''' Clean corona wires with brush
* '''50,000 pages:''' General cleaning and inspection
* '''100,000 pages:''' Replace transfer corona assembly
* '''200,000 pages:''' Replace fuser assembly
* '''300,000 pages:''' Major overhaul recommended


'''Regular Cleaning:'''
{| class="wikitable styled-table" style="width:80%;"
* Toner vacuum with appropriate filter
! Part !! Number
* Paper path cleaning with lint-free cloth
|-
* Corona wire cleaning with supplied brush
| '''Controller-I/O Board, LW II NT''' || '''661-0438'''
* Exterior wipe with damp cloth
|-
 
| DC Controller PCA || 661-0426
=== Memory Issues ===
|-
The 2 MB fixed RAM configuration limitations:
| DC Power Supply, 110/115 V || 661-0424
* Cannot be expanded
|-
* Insufficient for very complex documents
| DC Power Supply, 220/240 V || 661-0442
* May require document simplification
|-
* Font downloading limited by available memory
| Fuse, 125 V 6.3 A || 941-0005
 
|-
== Driver Software ==
| Fuse, medium time lag 3.15 A, 250 V || 740-0061
 
|-
=== Macintosh Support ===
| High-Voltage Power Supply || 661-0425
* '''System 6.0.3:''' Minimum requirement
|-
* '''System 7.0-7.5.5:''' Full support
| Laser/Scanner Assembly || 661-0423
* '''LaserWriter driver:''' Version 5.2 or later
|-
* '''Chooser extension:''' Standard AppleTalk
| '''Fuser Assembly, 110/115 V''' || 661-0440
 
|-
=== PC Support ===
| '''Fuser Assembly, 220/240 V''' || 661-0444
* '''MS-DOS:''' PostScript drivers available
|-
* '''Windows 3.x:''' PostScript driver support
| Fuser Heater, 100 V, '''620 W''' || 938-0003
* '''OS/2:''' Native PostScript support
|-
* '''Connection:''' RS-232 serial cable
| Fuser Heater, 220 V, '''570 W''' || 938-0004
 
|-
=== Printer Languages ===
| Fuser Roller Cleaner || 970-0049
* '''PostScript Level 1:''' Primary language
|-
* '''Diablo 630:''' Emulation mode for compatibility
| '''Ozone Filter''' || 961-0003
* '''HP LaserJet:''' Not supported (unlike IINTX)
|-
 
| Ozone Filter (for case with door) || 961-0007
== Service Information ==
|-
 
| Power Supply Block, 110/115 V || 661-0427
=== DIP Switch Settings ===
|-
Internal DIP switches for configuration:
| Power Supply Block, 220/240 V || 661-0443
* '''SW1-2:''' Interface selection (LocalTalk/Serial)
|-
* '''SW3:''' Diablo 630 emulation
| Distribution PCA || 971-0028
* '''SW4:''' Reserved
|-
* '''SW5-8:''' Diagnostic modes
| Transfer Corona Assembly || 971-0026
 
=== Test Points ===
DC controller board test points:
* +5V DC logic supply
* +24V DC motor supply
* -12V DC bias supply
* High voltage (special probe required)
 
=== Voltage Adjustments ===
* Print density: Potentiometer on DC controller
* Registration: Mechanical laser alignment
* No user-adjustable voltages
 
== Upgrade Options ==
 
=== Controller Board Upgrades ===
The IINT could be upgraded to:
* '''IIf board:''' PostScript Level 2, SCSI support
* '''IIg board:''' PostScript Level 2, Ethernet
 
'''Upgrade Process:'''
# Remove IINT controller board
# Install replacement board
# Update printer drivers
# Configure new features
 
=== Comparison with Downgrade ===
The IINT could replace IISC controller for PostScript:
* Adds PostScript Level 1
* Adds LocalTalk networking
* Adds 35 built-in fonts
* Increases processor speed
 
== Comparison with LaserWriter II Series ==
 
{| class="wikitable" style="width:95%; text-align:center;"
|+'''LaserWriter II Series Specifications'''
! Feature !! IISC !! IINT !! IINTX !! IIf !! IIg
|-
|-
| Processor || 68000 @ 7.45 MHz || 68000 @ 11.5 MHz || 68020 @ 16.67 MHz || 68030 @ 25 MHz || 68030 @ 25 MHz
| Transfer Guide Assembly || 971-0019
|-
|-
| RAM || 1 MB fixed || 2 MB fixed || 2-12 MB || 2-32 MB || 5-32 MB
| Paper Feed Roller Assembly || 971-0017
|-
|-
| PostScript || No || Level 1 || Level 1 || Level 2 || Level 2
| Feeder Assembly || 971-0018
|-
|-
| Fonts in ROM || 0 || 35 || 35 || 35 || 35
| Delivery Assembly || 971-0023
|-
|-
| LocalTalk || No || Yes || Yes || Yes || Yes
| Main Motor Assembly || 971-0014
|-
|-
| SCSI || Yes || No || Yes || Yes || Yes
| Fan, Lower || 959-0021
|-
|-
| Ethernet || No || No || No || No || Yes
| Fan, Upper || 959-0022
|-
|-
| HP PCL || No || No || Yes || Yes || Yes
| Status Panel || 971-0005
|-
|-
| Price (1988) || $2,999 || $4,599 || $5,999 || - || -
| Cleaning Brush || 970-0047
|-
|-
| Price (1991) || - || - || - || $3,599 || $4,599
| Mirror Assembly || 971-0007
|}
|}


== Compatibility ==
The DC power supply, fuser assembly, fuser heater and power supply block are '''different parts for 110 V and 220 V machines'''.<ref name="asg" /> The fuser heaters differ in wattage as well as voltage — 620 W at 100 V, 570 W at 220 V.
 
=== System Requirements ===
'''Macintosh:'''
* System 6.0.3 or later
* LaserWriter driver 5.2 or later
* LocalTalk or serial connection
 
'''Apple II:'''
* Apple IIgs with AppleTalk card
* Apple IIe with Workstation Card
 
'''PC:'''
* PostScript-aware application
* RS-232 serial port
* Appropriate driver software
 
=== Network Compatibility ===
* AppleTalk Phase 1 and Phase 2
* LocalTalk compatible
* PhoneNET compatible
* EtherTalk bridge compatible
 
== Service Manual ==
<pdf width="800" height="500">File:laserwriter_ii.pdf</pdf>


The LaserWriter II series service manual is available on the [[:Category:Apple Service Source|Apple Service Source]] page.
== Service Manuals ==
<pdf>File:Apple LaserWriter Printers Volume I.pdf</pdf>


== Successor Models ==
<pdf>File:Apple LaserWriter II Service Training Participant Manual Version 1.1 Oct 1992.pdf</pdf>


=== Personal LaserWriter NT ===
== See Also ==
Released July 1990 as lower-cost alternative:
* [[Apple LaserWriter II SC]]
* Reduced to 2 MB RAM (non-expandable)
* [[Apple LaserWriter]]
* Smaller footprint
* [[Apple LaserWriter Plus]]
* Lower price point
* [[Apple Personal LaserWriter 300]]
* Same 68000 processor
* [[LaserWriter II Service Source]]


=== LaserWriter IIf ===
== References ==
Released October 1991 as direct replacement:
* 68030 processor at 25 MHz
* PostScript Level 2
* 2-32 MB RAM expandable
* SCSI interface added
* PhotoGrade and FinePrint options


== Related Pages ==
<references />
* [[LaserWriter IISC]]
* [[LaserWriter IINTX]]
* [[LaserWriter IIf]]
* [[LaserWriter IIg]]
* [[LocalTalk]]
* [[PostScript]]


{{Navbox-AppleVintageAccessories}}
{{Navbox-AppleVintageAccessories|state=collapsed}}


[[Category:Apple Vintage Accessories]]
[[Category:Apple Vintage Accessories]]

Revision as of 19:43, 23 September 2026

Apple LaserWriter II NT
Apple LaserWriter II
Manufacturer Apple Computer, Inc.
Type Laser printer
Interface LocalTalk / RS-422 (mini DIN-8); RS-232 (DB-25); Apple Desktop Bus connector present
Compatible Macintosh; other computers via RS-232
Dimensions 8.6 in. H x 20 in. W x 18.5 in. D
Weight 45 lb (20.25 kg)
Power 90-126 V AC, 50-60 Hz

The Apple LaserWriter II NT is the PostScript member of the LaserWriter II range. It shares the Canon LBP-SX engine, the case, the power supply and the entire mechanical parts list with the II SC and the NTX; what makes it an NT is its controller-I/O board — a 68000 at 11.16 MHz with 1.0 MB of ROM and 2.0 MB of RAM, speaking PostScript and Diablo 630 over LocalTalk, RS-232 and RS-422.[1]

Before you take the covers off, read the Safety section. There is an invisible laser inside, a fuser that needs five minutes to cool, and a high-voltage supply for the coronas.

Controller-I/O Board

Apple's table for the whole range, which is the clearest single comparison available:[1]

Controller-I/O board specifications[1]
SC NT NTX IIf IIg
CPU 68000 (7.45 MHz) 68000 (11.16 MHz) 68020 (16.67 MHz) 68030 (20.0 MHz) 68030 (25.0 MHz)
ROM 16 KB 1.0 MB 1.0 MB 2.0 MB 2.0 MB
RAM 1.0 MB 2.0 MB 2.0 MB, expandable to 12 MB 2.0 MB, expandable to 32 MB 5.0 MB, expandable to 32 MB
I/O SCSI LocalTalk, RS-232, RS-422 LocalTalk, RS-232, RS-422, SCSI LocalTalk, RS-232, RS-422, SCSI LocalTalk, RS-232, RS-422, SCSI, Ethernet
Imaging languages QuickDraw PostScript, Diablo 630 PostScript, Diablo 630, HP LaserJet PostScript Level 1 & 2, HP LaserJet IIP PostScript Level 1 & 2, HP LaserJet IIP
Built-in fonts Times, Helvetica, Courier, Symbol Times, Courier, Symbol, Palatino, Helvetica, Helvetica Narrow, ITC Bookman, ITC Avant Garde, ITC Zapf Chancery, New Century Schoolbook, ITC Zapf Dingbats as NT as NT as NT

Three things in that table are commonly misreported. The NT runs at 11.16 MHz, not 11.5. The IIf runs at 20.0 MHz, not 25.0 — the IIg is the 25 MHz machine. And Apple's guide gives eleven font families, not a font count; the familiar "35 fonts" figure is a count of individual styles that Apple's service documentation does not state, so it is not given here.

The NT's 2.0 MB is not expandable. Apple documents memory upgrades for the NTX and for the IIf/IIg only; there is no NT memory upgrade in the guide.[1]

Board layout

Apple's service course diagram of the NT controller-I/O board shows an MC68000, a 6532 VIA, an 8530 SCC, 1 MB of ROM, 2 MB of RAM and a bank of SRAMs, with the Apple Desktop Bus connector, a two-position switch, the RS-232 port and the LocalTalk/RS-422 port along the back panel. The board mates with the print engine through a 32-pin right-angle connector that engages as the board slides into the guide rails in the base of the engine.[2]

Board and ROM part numbers

NT controller-I/O board[1]
Part Number
Controller-I/O Board, LW II NT 661-0438
IC, ROM, L0 342-0545
IC, ROM, H0 342-0546
IC, ROM, L1 342-0547
IC, ROM, H1 342-0548
IC, ROM, L2 342-0549
IC, ROM, H2 342-0550
IC, ROM, L3 342-0551
IC, ROM, H3 342-0552

Eight ROMs in high/low pairs, L0/H0 through L3/H3. A board with a different ROM complement is not an NT board: the NTX takes eight differently numbered ROMs (342-0560 to 342-0567, or 342-0711 to 342-0718 on the rev 3 board), and the IIf and IIg take four (076-0860 to 076-0863).[1]

Ports and Switches

The NT's rear panel carries, left to right, an Apple Desktop Bus connector, a switch bank, the RS-232 port and the LocalTalk/RS-422 port.[1]

The ADB connector is present on the SC, NT and NTX and was removed on the IIf and IIg, which use a pushbutton switch instead.[1] Apple's guide documents its presence but describes no function for it, so none is claimed here.

RS-422 / LocalTalk — mini DIN-8 male (shared with the NTX, IIf, IIg and Personal LaserWriter NT)[1]
Pin Signal Description
1 HSKo Handshake out
2 HSKi Handshake in
3 TxD− Transmit data −
4 SG Signal ground
5 RxD− Receive data −
6 TxD+ Transmit data +
7 GPi General-purpose input
8 RxD+ Receive data +
RS-232 — DB-25 male[1]
Pin Signal Description
1 SGND Signal ground
2 TxD Transmitted data
3 RxD Received data
4 RTS Request to send
5 CTS Clear to send
6 DSR Data set ready
7 SG Signal ground
8 DCD Data carrier detect
20 DTR Data terminal ready
22 RI Ring indicator

Switch configurations

The NT has two switches, not a bank of eight. Apple's table is short enough to memorise, and a printer that will not talk to anything is very often simply set to the wrong one:[1]

LaserWriter II NT switch configurations[1]
Communication and command mode 1 2
LocalTalk Up Up
Diablo 630 emulation Down Up
9600 baud RS-232 & RS-422 Up Down
1200 baud RS-232 & RS-422 Down Down

Those are the only two serial rates the NT offers. The NTX adds a six-switch bank with separate command-mode and handshaking groups, including a PostScript interactive mode and an HP LaserJet mode; the NT has neither.[1]

Apple's cable for the NT is the LocalTalk Connector Kit, DIN-8, service part 590-0338 or 630-8275, Apple model M2068 — the same kit used by the NTX, IIf, IIg and Personal LaserWriter NT.[1]

LaserWriter II print engine specifications[1]
Marking engine Canon LBP-SX laser xerographic
Print resolution 300 dots per inch
Speed 8 pages per minute
Print materials Letter, legal, A4 and B5 sizes use 16–20 lb single-sheet photocopy bond, 8–34 lb letterhead and coloured stock, or transparency overhead film. Envelopes, labels and paper up to 36 lb via manual feed; envelopes also via an optional envelope tray
Print capacities Paper cassettes hold 200 sheets of 20-lb paper. Envelope cassette holds 15 envelopes
Printable surface Letter 8.0 × 10.5 in.; Legal 8.0 × 13.0 in.; A4 7.41 × 10.86 in.; B5 7.69 × 10.16 in.
Physical dimensions Height 8.6 in. (21.8 cm); width 20 in. (50.8 cm); depth 18.5 in. (47 cm); weight 45 lb (20.25 kg)
Operating environment 50 to 90 °F (10 to 32.5 °C); humidity 20% to 80%
Power requirements 90 to 126 volts AC; 50 to 60 Hz

The cassette holds 200 sheets, not 250. Apple's guide gives no wattage, current draw, BTU figure, acoustic noise level, rated engine life, monthly duty cycle or first-page-out time for the LaserWriter II, and none is stated here.

The four subsystems

Apple's service course splits the engine into four, and the split is the fastest way to localise a fault:[2]

  • Power distribution — the AC inlet and power switch, the AC driver board and fuser heater, the DC power supply/motor driver PCA, the high-voltage power supply feeding the primary corona, transfer corona and developing bias, and the distribution PCA.
  • Control — the DC controller PCB, which receives the print command from the controller-I/O board, drives everything else and reports engine status on the front-panel LEDs. Apple's advice is explicit: always check the DC controller as part of troubleshooting, because a module that looks faulty may simply never have received its command or its supply.
  • Image formation — laser diode, scanning motor and optical fibre, photosensitive drum, coronas, static-charge eliminator, toner sensor and fuser.
  • Pickup/feed — cassette, pickup and registration rollers, their solenoids and the paper sensors.

Sensors, switches and solenoids

Real designators, for probing rather than guessing:[2]

Designator Where What it does
PS301 Distribution PCA Paper-out sensor — senses paper in the cassette
PS302 Distribution PCA Manual feed sensor — shares its arm with PS301
PS331 Fuser PCA / fuser assembly PCA Paper delivery sensor. Paper that fails to reach and clear it in time is the jam
SL301 Distribution PCA Pickup roller solenoid — engages the clutch that turns the pickup roller
SL302 Distribution PCA Registration roller clutch solenoid — feeds paper towards the drum
SW301, SW302 Distribution PCA Drum-sensitivity switches, read from the cams on the toner cartridge so the DC controller can match laser intensity to the drum
Interlock switch Top of the DC power supply Cuts power when the upper unit opens; the interlock lever presses it when the unit closes

Two of those explain faults that are otherwise baffling. PS301 and PS302 share one arm, so a bent or sticking arm can produce a paper-out indication and a manual-feed fault at once. And a jam reported with no paper in the machine is normally PS331 or its timing, not the paper path.

Safety

The LaserWriter family safety rules apply in full:[1]

  • High voltage. Switch off and disconnect the AC power cord before servicing. Certain parts are electrified under power. Never work on the printer under power except when making live adjustments.
  • Laser. Do not disconnect the optical fibre cable when the printer is powered on. The fibre carries the infrared laser beam, which you cannot see but which can permanently damage your eyes. When servicing the optical system, do not put screwdrivers or other shiny objects in the beam path — the reflected beam is equally dangerous. Apple's own warning labels inside the covers read "DANGER — INVISIBLE LASER RADIATION WHEN OPEN. AVOID DIRECT EXPOSURE TO BEAM."
  • Fuser. The fuser rollers become very hot. Switch off for at least five minutes before servicing them.
  • Do not touch, with covers off and power on: the high-voltage power supply, the DC power supply, or the power supply block, which is the LaserWriter II-specific item on Apple's list.
  • Do not be grounded when working on plugged-in equipment or making live adjustments, and remove all jewellery before you start.
  • ESD. The controller-I/O board contains CMOS parts, and CMOS chips, ROMs and SIMMs are very susceptible to electrostatic discharge and skin acid. Handle them by the edges only.
  • Weight. 45 lb. Apple warns about lifting LaserWriters for good reason.
  • Toner is non-toxic — plastic, iron and a little pigment. Remove as much as possible with a dry tissue, then wash with cold water; hot water gels it and fuses it permanently into fabric. Toner attacks vinyl.
  • Never use an ammonia-based cleaner on the LaserWriter II — it discolours the plastic.

Status LEDs

There are four, all on the front panel, and none of them is a "Service" light.[1][2]

LaserWriter II status LEDs[1]
LED Colour Behaviour
Ready Green Flashes during warm-up and while the printer is operating. Steady when warmed up and ready. Off when the printer is not ready, an error condition exists, or the top cover is open
Low-Toner Orange On and steady when the toner cartridge needs replacement. Flashes when the cartridge is installed incorrectly
Paper-Out Red On and steady when out of paper or the paper tray is missing. Flashes when the printer is ready to accept manually fed paper
Paper Jam Red Comes on when paper jams and stays on until the jam is cleared

The error indication is a combination, not a light of its own:[1]

> When both the red Paper-Out and Paper Jam lights flash, the controller-I/O board or the print engine has an error condition.

Things that are not faults

  • A new toner cartridge that leaves the Low-Toner LED on. Apple documents this for the NT specifically: after a new cartridge goes in, the Low-Toner LED stays lit until the printer produces a printout, or until you switch it off and on again.[1]
  • A flashing Low-Toner LED means the cartridge is seated wrongly, not that it is empty.
  • A flashing Paper-Out LED means the printer is waiting for you to hand-feed a sheet.
  • The Ready LED going off is how the printer reports trouble — there is no separate service lamp to look for.

Test Pages

Two pages, testing the two halves of the machine. Knowing which is which halves the diagnostic problem immediately.[1]

Engine self-test page — tests the print engine

Press the engine self-test switch, located on the side of the printer behind the access cover.[1] This runs the print engine alone — no computer, no network, no driver — and is how you isolate engine failures from controller-I/O board failures.

Startup test page — tests the controller-I/O board

The NT generates a startup test page every time it is switched on, unless the user has switched the function off with PostScript software or with the LaserWriter Utility on the LaserWriter II Installation disk.[1] It confirms the controller-I/O board and carries the page count.

So: a fault on the engine self-test page is in the engine. A machine that prints a clean engine self-test but no startup test page has a controller-I/O board fault. A machine that passes both but will not print from the Macintosh has a cable, switch-setting, driver or host problem — and on an NT, check the two-position switch before anything else.

Troubleshooting

Pre-power-on checklist

Apple's list, to be worked through before the flowcharts:[1]

  • Line voltage is OK — 115 volts AC ±10%
  • Printer is on a solid, level surface
  • Room temperature 50–90 °F (10–32.5 °C), humidity 20%–80%
  • Not in a hot, humid or dusty area, nor near open flames
  • Printer is not exposed to ammonia gas
  • Not in direct sunlight; well ventilated
  • Cables and connectors are OK
  • Toner cartridge installed and has toner
  • Fuser roller cleaner felt is in place and not dirty
  • Print density adjustment dial set correctly
  • Paper cassette properly loaded and paper within specification
  • Transfer corona wire clean and unbroken
  • I/O PCA DIP switches are set correctly

The ammonia item is not a curiosity — diazo copiers and some cleaning products produce it, and it will degrade the machine.

Troubleshooting order

Apple's sequence is fixed: check the pre-power-on list; be familiar with the safety section before any live electrical check; for an SC or NT/NTX begin with Troubleshooting Flowchart 1 and proceed function by function until every main function is verified; if you replace a module and the problem remains, reinstall the original before proceeding; and perform preventive maintenance before returning the printer.[1]

The IIf/IIg status-LED diagnostic does not apply to the NT. That procedure — rear rotary switch to 4, LaserWriter II Test Connector on the DB-25 port, read the LEDs against a table — exists only on the IIf and IIg.[1]

Laser power output check

Apple's procedure, which needs a laser power checker and a digital multimeter. The check figure is 17.6 mV ± 1.6 mV.[1]

  1. Put the printer on a grounded workbench pad and remove the controller-I/O board and the cover set.
  2. With the power off, open the laser access hatch on the laser/scanner assembly.
  3. Insert the laser power checker into the hatch with the detector facing the laser diode.
  4. Black lead to the meter's "Common" socket, red lead to "Volts"; set the meter to volts, 200 mV range.
  5. Defeat the top cover interlock switch with a nonmetallic tool, switch on and wait one minute for warm-up.
  6. Depress drum-sensitivity switches SW301 and SW302 below the top cover interlock switch, and press the service test print button.
  7. Read the meter. 17.6 mV ± 1.6 mV.

If the power cannot be measured at all, Apple's order is to replace the laser/scanner assembly and repeat, and if it still cannot be measured, the DC controller PCA.[1] Note that this procedure defeats the cover interlock deliberately: the laser is running with the covers off, and the safety rules above apply at their strictest.

Preventive Maintenance

Before starting

Power off and unplug; let the fuser assembly rollers cool; prepare the work area for ESD; spread a drop cloth against grease and spilled toner.[1]

Page count

Switch on and wait for the startup test page. The number at the bottom is the pages printed since the controller-I/O board was installed — accurate only if that board has never been repaired or upgraded. If it has, Apple's instruction is to check the Repair Log Label on the bottom of the printer and ask the customer.[1]

Apple's parts replacement schedule

Every 50,000 prints: replace the ozone filter and check the fan.[1]

Every 100,000 prints, replace:[1]

  • Fuser assembly
  • Transfer guide assembly
  • Preconditioning exposure assembly
  • Paper feed roller assembly
  • Transfer corona assembly

That is the whole schedule. Apple's guide has no monthly, annual-by-page-count or 200,000/300,000-print item for this machine, and the ozone filter — a genuine consumable that is very often never changed — is the one most worth acting on.

Cleaning

Service points and what to use[1]
Service point Tool or solvent
Primary corona wire Cleaning brush supplied with the printer
Transfer corona wire Cotton swab (with isopropyl alcohol, for user cleaning)
Transfer guide Cloth dampened with water
Fuser rollers Fuser cleaning pad
Exterior case Cloth dampened with water
Separation claws Cloth dampened with alcohol
Paper guide Cloth dampened with alcohol
Lower delivery guide Cloth dampened with alcohol
Feeder guide Cloth dampened with water
Registration rollers Cloth dampened with water

Apple splits these into items the customer cleans as needed (the first five) and a dealer list to be done every 12 months or at each service call (all ten).[1] Note which points take water and which take alcohol — they are not interchangeable.

Parts

Selected entries, common to the LaserWriter II range except where the NT is named:[1]

Part Number
Controller-I/O Board, LW II NT 661-0438
DC Controller PCA 661-0426
DC Power Supply, 110/115 V 661-0424
DC Power Supply, 220/240 V 661-0442
Fuse, 125 V 6.3 A 941-0005
Fuse, medium time lag 3.15 A, 250 V 740-0061
High-Voltage Power Supply 661-0425
Laser/Scanner Assembly 661-0423
Fuser Assembly, 110/115 V 661-0440
Fuser Assembly, 220/240 V 661-0444
Fuser Heater, 100 V, 620 W 938-0003
Fuser Heater, 220 V, 570 W 938-0004
Fuser Roller Cleaner 970-0049
Ozone Filter 961-0003
Ozone Filter (for case with door) 961-0007
Power Supply Block, 110/115 V 661-0427
Power Supply Block, 220/240 V 661-0443
Distribution PCA 971-0028
Transfer Corona Assembly 971-0026
Transfer Guide Assembly 971-0019
Paper Feed Roller Assembly 971-0017
Feeder Assembly 971-0018
Delivery Assembly 971-0023
Main Motor Assembly 971-0014
Fan, Lower 959-0021
Fan, Upper 959-0022
Status Panel 971-0005
Cleaning Brush 970-0047
Mirror Assembly 971-0007

The DC power supply, fuser assembly, fuser heater and power supply block are different parts for 110 V and 220 V machines.[1] The fuser heaters differ in wattage as well as voltage — 620 W at 100 V, 570 W at 220 V.

Service Manuals

See Also

References

  1. ↑ 1.00 1.01 1.02 1.03 1.04 1.05 1.06 1.07 1.08 1.09 1.10 1.11 1.12 1.13 1.14 1.15 1.16 1.17 1.18 1.19 1.20 1.21 1.22 1.23 1.24 1.25 1.26 1.27 1.28 1.29 1.30 1.31 1.32 1.33 1.34 1.35 Apple Service Guide for LaserWriter Printers, Volume I, Apple Computer, Inc., January 1992 (072-0631-B) — hosted on this wiki as File:Apple LaserWriter Printers Volume I.pdf. Covers the LaserWriter, LaserWriter Plus, LaserWriter II SC/NT/NTX/IIf/IIg and Personal LaserWriter SC/NT/LS. Introductory safety section: the high-voltage, optical-fibre, fuser-cooling, ESD, not-being-grounded and lifting warnings; the LaserWriter Safety Rules; the toner-safety paragraph; the laser-safety paragraph and the three laser warning labels. Tab 3, LaserWriter II: parts list including the NT controller-I/O board and its ROM set (pages 4–5); controller-I/O board specifications (page 10); print engine specifications (page 11); status LEDs (page 12); test pages (page 13); the pre-power-on checklist, the troubleshooting flowcharts and tables including the NT low-toner note (pages 14–54); the laser power output check (page 55); and preventive maintenance including the page count, the parts replacement schedule and the user and standard maintenance tables (pages 59–60). Tab 6, Ports and Cables: the peripheral cable table, external connector diagrams, the RS-422 and RS-232 pin-outs and the LaserWriter II NT switch configuration table.
  2. ↑ 2.0 2.1 2.2 2.3 Apple Service Training: LaserWriter II Service Course, Participant Manual, Version 1.1, Apple Computer, Inc., October 1992 — hosted on this wiki as File:Apple LaserWriter II Service Training Participant Manual Version 1.1 Oct 1992.pdf. Module 1, "LaserWriter II Parts and Functions": the SC, NT and NTX I/O board block diagrams and back panels (figures 1-3 to 1-5) and the 32-pin right-angle engine connector; the four-subsystem breakdown (power distribution, control, image formation, pickup/feed); the power distribution diagram (figure 1-7); the DC controller PCB's role; the interlock switch at the top of the DC power supply; the status panel description; the distribution PCA (figure 1-12) with drum-sensitivity switches SW301 and SW302, pickup solenoid SL301, registration clutch solenoid SL302, paper-out sensor PS301 and manual feed sensor PS302; and paper delivery sensor PS331 on the fuser PCA.


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