Apple LaserWriter II NT
| 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]
| 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
| 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.
| 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 + |
| 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]
| 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]
Print Engine
| 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]
| 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]
- Put the printer on a grounded workbench pad and remove the controller-I/O board and the cover set.
- With the power off, open the laser access hatch on the laser/scanner assembly.
- Insert the laser power checker into the hatch with the detector facing the laser diode.
- Black lead to the meter's "Common" socket, red lead to "Volts"; set the meter to volts, 200 mV range.
- 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.
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 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
- Apple LaserWriter II SC
- Apple LaserWriter
- Apple LaserWriter Plus
- Apple Personal LaserWriter 300
- LaserWriter II Service Source
References
- ↑ 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.
- ↑ 2.0 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.