Apple LaserWriter II Troubleshooting Guide

The DC controller board seen from below, from Apple's Service Source: the connectors used in the voltage checks, LED201, the service test page button, the cover interlock switch and C211.

Fault-finding for the Apple LaserWriter II range: the II SC, II NT, II NTX, IIf and IIg. All five use the same Canon LBP-SX engine, and Apple's Service Source says every part except the I/O board is interchangeable between them. The symptom tables below are Apple's, from the January 1992 Apple Service Guide for LaserWriter Printers, Volume I, reduced to the checks and readings. The guide lists each fix in order: try the first, and move to the next only if the fault remains. Cleaning, parts replacement and the safety rules are on Apple LaserWriter II General Maintenance.

Safety for live checks

Many of Apple's checks are made with the printer running and the covers off.

• The laser is infrared and invisible. Never open the laser access hatch or disconnect the optical fibre cable with the printer switched on.
• Several checks need the top-cover interlock defeated. Apple's method is a stiff non-metallic insert in the interlock switch, such as a plastic pen cap or a folded index card. This lets the engine run, and the laser fire, with the top unit open.
• With covers off and power on, keep clear of the high-voltage power supply, the DC power supply and the power supply block, which carry mains or high voltage.
• The fixing rollers run at about 400 °F (about 200 °C). Apple says to leave the printer off for at least 5 minutes before touching them.
• Keep the printer upright during a print cycle and whenever the clamshell is open. Apple's way to reach the DC controller board for voltage readings is to rest the printer on the I/O board rails with the rear towards you, using the bottom panel and lower cover to raise it if needed.

Apple's tools for this work were the Laser Power Checker (076-0121), the SIMM removal tool (076-8354), the LaserWriter II Test Connector (077-8319) and a multimeter.

Before switching on

Apple's pre-power-on checklist:

• Mains 115 V AC ±10% (on a US printer).
• Printer on a solid, level surface, out of direct sunlight, in a ventilated room at 10-32.5 °C (50-90 °F) and 20-80% humidity, away from flames, dust and ammonia gas.
• Cables and connectors sound.
• Toner cartridge fitted and not empty.
• Fuser roller cleaner felt in place and clean.
• Print density dial set correctly.
• Cassette loaded correctly with paper within specification.
• Transfer corona wire clean and unbroken.
• I/O board switches set correctly.

If a replacement module does not cure a fault, refit the original before going on.

Status lights

The four front-panel lights, from left to right, are Ready (green), Low Toner (orange), Paper Out (red) and Paper Jam (red).

Status lights (Apple Service Guide, Tab 3 p. 12)

Light	Steady	Flashing	Off
Ready	Warmed up and ready	Warming up, or printing	Not ready, an error, or the top cover is open
Low Toner	Cartridge needs replacing	Cartridge fitted incorrectly
Paper Out	Out of paper, or no cassette	Waiting for a hand-fed sheet
Paper Jam	Paper jammed (stays on until the jam is cleared)

Paper Out and Paper Jam flashing together mean an error in the controller-I/O board or the engine.

Things that are not faults

• On a II NT, the Low Toner light stays on after a new cartridge is fitted until the printer has made a print or been switched off and on.
• Low Toner can come on because the toner needs redistributing. Take the cartridge out, rock it gently a few times and refit it. If the light goes out, keep using the cartridge.
• With the I/O board removed, the front-panel lights do not work.
• The startup page takes about 2-3 minutes to appear after switch-on.
• Blotchy printing or ghosting on the first rotation of the drum is a known limitation. Apple's fix is to move the image below the 94 mm mark from the top of the page.

Test pages

• Service (engine self-test) page. Generated by the DC controller board alone and checks only the engine. Remove the bottom panel cap at the rear and press the button through the 1/4 in hole with a screwdriver or dowel. Apple's 1992 guide describes the same switch as being on the side of the printer behind the access cover.
• Startup page (NT, NTX, IIf, IIg). Printed at each switch-on unless turned off in software; it confirms the controller-I/O board works and shows the I/O board's page count.
• II SC. The SC prints a test page of vertical lines only when its SCSI address is set to 7 before power-on. Set the address back before printing from a Macintosh, which is always ID 7.

A good service page and no startup page means the controller-I/O board. A fault on the service page is in the engine.

IIf and IIg self-diagnostic

Set the rotary switch on the back to 4, fit the LaserWriter II Test Connector to the DB-25 serial port (or jumper pins 4 and 22), and switch on. The lights flash during startup and then hold the "diagnostic executing" pattern for about 2 minutes. If no error is found, all four lights flash and a page prints. Afterwards switch off, remove the connector and return the switch to its original setting.

IIf/IIg diagnostic codes (Ready, Low Toner, Paper Out, Paper Jam)

Ready	Low Toner	Paper Out	Paper Jam	Service Source (1995)	Service Guide (January 1992)
Off	On	Flash	Flash	Diagnostic executing	Scanner assembly error (table K)
Flash	Flash	Flash	Flash	No error found	No error
On	On	Flash	Flash	Fuser assembly error	Fuser assembly (table D)
On	Off	Flash	Flash	Laser/scanner error	Laser assembly (table K)
Off	Off	Flash	Flash	I/O controller board error	Controller-I/O board (table C)
Off	On	Off	Off	Replace ROM 1	Replace ROM 1
Off	On	Off	On	Replace ROM 2	Replace ROM 2
Off	On	On	Off	Replace ROM 3	Replace ROM 3
Off	On	On	On	Replace ROM 4	Replace ROM 4
On	Off	Off	Off	Replace SIMM 1	Replace SIMM 1
On	Off	Off	On	Replace SIMM 2	Replace SIMM 2
On	Off	On	Off	Replace SIMM 3	Replace SIMM 3
On	Off	On	On	Replace SIMM 4	Replace SIMM 4
On	On	Off	Off	Replace SIMM 5	Replace SIMM 5
On	On	Off	On	Replace SIMM 6	Replace SIMM 6
On	On	On	Off	Replace SIMM 7	Replace SIMM 7
On	On	On	On	Replace SIMM 8	Replace SIMM 8

The two Apple documents disagree on the first row. The later Service Source shows Off-On-Flash-Flash as the pattern while the test runs, and has a single laser/scanner error. The 1992 Service Guide uses the same pattern for a scanner fault and gives the laser its own code. If the lights hold Off-On-Flash-Flash for well over 2 minutes, treat it as a possible scanner fault.

Apple's fault-finding order

For the SC, NT and NTX, Apple starts at Flowchart 1 and checks one function at a time; for the IIf and IIg it starts with the self-diagnostic.

1. Functional check. Clear any jam, load paper, fit a toner cartridge, switch on and wait 60 seconds. Read the lights: Paper Out with paper loaded goes to table H, a false jam to table F, a false Low Toner to table L, an engine error to the engine-error chart. Then print a directory from a Macintosh (communication tables C1-C6) and a manual-feed page (table E).
2. Engine check. If the startup page does not print, press the engine self-test switch. A good service page means the controller-I/O board; no page means the engine check.
3. Engine check, in order: with the cover set off, the cassette refitted and the top cover closed, look for power (table A), for the delivery rollers turning (table B), for the fuser heater bulb lighting, seen through the opened face-up tray (table D), and for the preconditioning lamps (table J). Then pull the cassette and check Paper Out lights (table I). With the I/O board, bottom panel and lower cover removed and the printer upright on a padded surface, switch on, wait 45 seconds, press the engine self-test switch and watch LED201 on the DC controller.
4. Engine error (both red lights flashing). Switch off, wait one minute, switch on and look at the fuser bulb. If it does not light, table D; if it lights, Apple's next step is a new controller-I/O board.

Power and drive

Table A, no power, and table B, delivery rollers do not turn

Check	Reading or condition	Action
Outlet, power switch, top cover	Mains present; top cover shut; interlock lever intact	Plug in, try another outlet, close the cover, or replace the interlock lever
Circuit breaker CB1	Open	Reset CB1. If it trips again at switch-on there is a short to find
Fuse FS1 (F1) in the DC power supply	Open	Replace with a 125 V, 6.3 A fuse
Unplug, remove the DC power supply, plug back in, close the cover and switch on; measure across the outer two pins of J502	Voltage present	Present: replace the DC power supply. Absent: replace the power supply block
DC controller J212-4 (+5 V) to J212-1 (GND)	No +5 V	Replace the DC power supply
J212-7 (REMOTE*) to J212-1	Falls from about +4.5 V to 0 V at switch-on	Falls: replace the DC power supply. Does not fall: replace the DC controller PCA
Table B: open the top cover, hold the interlock and drum-sensitivity switches, switch on	The main motor should turn to its home position about 1 second after switch-on	If it turns, look for obstructions at the delivery coupler and rollers; if not, look for foreign objects in the drive gear and paper feed drive
Main motor cable	Seated in DC power supply connector J3	Reconnect it
J3 pins 1-4 to J3-5 (GND), cable unplugged, during an engine self-test	About +1.4 V one second after switch-on	Voltage present: replace the main motor
DC controller J212-8, -9, -10, -11 to J212-1, switching off and on for each	About +1 V one second after switch-on	Present: replace the DC power supply. Absent: replace the DC controller PCA

Apple's service course adds two power faults. If CB1 trips, power does not reach the fan, so nothing at all happens at switch-on. A jammed or binding main motor draws enough current to blow the main motor fuse on the DC power supply/motor driver board; a printer that groaned and stopped, then will not start after a stray sheet is cleared from the drive gear, has blown that fuse.

Fuser

When the fusing system fails, the DC controller cuts current to the fuser heater and charges capacitor C211 on the DC controller board. The printer stays in the error state until C211 discharges. The Service Source says about 30 minutes; the 1992 Service Guide says 20 to 30 minutes. To clear it at once:

1. Switch off and unplug the printer.
2. Remove the bottom panel and the lower cover.
3. Find C211 on the DC controller board (top right in the drawing above).
4. Short the two wires at the base of C211 with a conductive tool. Apple illustrates a length of lead solder, which bends easily and is less likely to damage the board than a screwdriver; take care not to touch neighbouring parts or tracks.

Replace the failed fuser part as well. Discharging C211 alone only clears the error.

If interlock switch SW205 on the DC controller is not properly installed, mains to the heater bulb can be cut off. With the lower cover off, check that the interlock lever can press SW205.

Table D, heater bulb does not light

Check	Expected	If not
Fuser out: thermoprotector TP1	Continuity	Replace the fuser assembly
Fuser out: thermistor, fuser PCA J331-4 (FSRTH) to J331-5 (GND), at room temperature	1 to 1.6 MΩ	Replace the fuser assembly. If the fault stays, check the cable from J331 to DC controller J206, then replace that cable
Fuser out: heater bulb across fuser connector J103	Continuity	Replace the heater bulb
Fuser refitted, I/O board, cover set, bottom panel and lower cover off, cartridge in, top cover shut: DC controller J208-2 (FSRD) to J208-3 (GND) at switch-on	Falls from about +5 V to 0 V	Falls: replace the power supply block and discharge C211; if the fault stays, check and then replace the cable from the power supply block (J101) to the DC controller (J208). Does not fall: replace the DC controller PCA

The Service Source gives a shorter test of J103: continuity between its two pins means both the fuser bulb and the thermoprotector are intact. J103 connects the fuser to the fuser safety PCA in the power supply block.

Paper handling

The distribution board above the DC power supply, from Apple's Service Source: drum sensitivity switches SW301 and SW302, paper-out sensor PS301, manual-feed paper sensor PS302, the pickup and registration solenoids (both labelled SL302 in Apple's drawing) and connector J213.

Tables E-I and N, paper feed and sensing

Symptom	Checks, in Apple's order
Manual feed does not work (E)	DC controller J213-9 (MPFS*) to J213-6 (GND): slide a sheet in until it trips PS302; the reading should fall from +5 V to 0 V. If it does, replace the DC controller PCA; if not, the distribution PCA
Jam reported with no paper in the printer (F)	Paper Jam lit at switch-on: look for fragments. Delivery-sensing lever in the fuser damaged, broken or the old version: replace it. Remove the fuser's left contact cap, switch on and measure fuser PCA J331-6 to J331-7 while moving the lever: +5 V to 0 V means check the cabling and then replace the DC controller PCA; no change means replace the fuser assembly
Jams not detected (G)	Delivery-sensing lever damaged, obstructed or not returning (Apple notes some wear so they stay out after a page passes): replace it. Then the J331-6/J331-7 test as above: a change means replace the DC controller-to-fuser cable and then the DC controller PCA; no change means replace the fuser assembly
Paper Out lit with paper loaded (H), or not lit with no paper (I)	Cassette loaded and seated; cassette undamaged; paper-sensing arm moves freely; cassette microswitch actuator levers straight; microswitches SW201-SW203 on the DC controller undamaged (if damaged, replace the DC controller PCA). DC controller J213-8 (PEMP*) to J213-6 should toggle between +5 V with the cassette in and 0 V with it out: if it does, replace the DC controller PCA; if not, the distribution PCA
No pickup from the cassette (N1)	Stuck paper inside; delivery rollers turn briefly at switch-on as the motor homes (if not, table B); J213-4 (CPUD) to J213-6 should go from 0 V to about +5 V two seconds after the main motor starts in an engine self-test: if so, replace the distribution PCA, if not, the DC controller PCA
Jams at pickup or transfer (N2)	Paper type, curl, more than 200 sheets, cassette seating and springs, pickup roller clean (alcohol) and unworn, registration clutch spring, bent upper transfer guide, then J213-4 (CPUD) and J213-3 (REGD) each rising to about +5 V two seconds after the motor starts
Jams at separation or the feeder guide (N3)	Clean the contact between the discharging pins and the high-voltage power supply. If jams continue, replace the high-voltage power supply
Jams at the fuser or delivery (N4)	Fuser cleaner felt; upper and lower paper guides; separation claws dirty or worn; delivery-sensing lever damaged or the old version; fuser assembly; worn delivery rollers
Sheets stuck together (N5)	Paper type; cassette springs; then the separation pad
Wrinkles (N6)	Paper; cassette tray; open the top cover about five seconds after pickup during an engine self-test: wrinkled at the feeder guide means the pickup or registration rollers, otherwise clean the fuser

The manual-feed sensor PS302 uses the same arm as the paper-out sensor PS301, and Apple's tables H and I both check that the paper-sensing arm moves freely.

Laser, scanner and low toner

Table K, laser/scanner fault; table L, false Low Toner; table J, preconditioning lamps

Check	Expected	Action
Scanner motor PCA J401 to DC controller J203; laser driver PCA J451 to DC controller J202	Seated	Reseat
Optical fibre between the laser/scanner and DC controller J201	Seated and undamaged	Reseat or replace the cable
Laser power output check	17.6 mV ±1.6 mV	Low: replace the laser/scanner assembly, then the laser harness cable. Correct: replace the DC controller PCA
Table L: cartridge has its drum-sensitivity cam	Yes	Otherwise replace the cartridge
SW301 and SW302 operated when the cartridge is in and the cover shut	Yes	Otherwise replace the distribution PCA
DC controller J213-1 and J213-2 to J213-6 while pressing SW301 and SW302 (cover open, interlock held)	Each falls from +5 V to 0 V	Otherwise check the J213 connection, then replace the distribution PCA
High-voltage power supply contacts	Clean and undamaged	Clean them; if damaged replace the high-voltage power supply; otherwise replace the DC controller PCA
Table J: fuser PCA J333 (+24 V) to J334 (GND), cover open, interlock held, at switch-on	Rises from 0 V to +24 V	Rises: replace the preconditioning exposure assembly
DC controller J206-3 (PEXP) to J206-5 (GND) at switch-on	Rises from 0 V to +5 V	Rises: replace the fuser assembly. Does not: replace the DC controller PCA

Laser power output check

1. Put the printer on an earthed bench mat 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 and insert the laser power checker with its detector facing the laser diode.
3. Connect the checker's black lead to the meter's common socket and the red lead to volts. Set the meter to the 200 mV range.
4. Defeat the top cover interlock with a non-metallic tool, switch on and wait one minute.
5. Hold drum-sensitivity switches SW301 and SW302 (below the interlock switch) and press the service test print button.
6. Read 17.6 mV ±1.6 mV. With no reading, replace the laser/scanner assembly and repeat; if there is still none, replace the DC controller PCA.

No adjustment can be made to the laser power circuitry of the LaserWriter II, and the laser/scanner is sold only as a complete assembly. The Service Source lists the Laser Power Checker (076-0121) as discontinued.

Print quality

Two quick tests narrow most image faults before the tables.

• Repeated marks. Measure the spacing between repeats and match it to a roller.
• Drum check. Stop a print cycle part-way and look at the image on the drum. If the drum shows the same fault as the page, the fault is before the drum, probably in the scanning system. If the drum image is good, look at the fuser, the transfer corona or the high-voltage supply.

Repeat spacing by roller (LaserWriter II Service Source)

Assembly	Roller	Repeat
Transfer guide	Roller to corona assembly	0.5 in (13 mm)
Transfer guide	Upper metallic roller	1.5 in (38 mm)
Transfer guide	Lower black roller	1.75 in (44 mm)
Fuser	Lower fuser roller	2.56 in (65 mm)
Fuser	Upper fuser roller	3.16 in (80 mm)
Toner cartridge	Developer roller	2.0 in (51 mm)
Toner cartridge	Photosensitive drum	3.75 in (95 mm)

Print quality tables M1-M23 (Apple Service Guide, Tab 3 pp. 36-50)

Table	Symptom	Apple's checks, in order
M1	Light or faded print	Density dial up one step; Low Toner lit (new cartridge); new cartridge not shaken (rock it); refilled cartridge; damp or wrong paper; transfer corona wire dirty or broken; SW301 and SW302 at J213-1/J213-2; then the high-voltage drive signals (below); then the high-voltage power supply, then the laser/scanner
M2	Dark print	Density dial down one step; SW301 and SW302; toner cartridge grounding spring TB602 on the high-voltage supply clean and touching (damaged spring: replace the supply); then the laser/scanner, laser harness cable and DC controller
M3	All-blank page	Low Toner lit; Paper Out and Paper Jam flashing (replace the laser/scanner); sealing tape left in the cartridge; cartridge shield and laser shutters moving freely; shutter assembly over the mirror; broken transfer corona wire; J401/J203 and J451/J202 seated; laser power check; J601-6 and J601-4 signals
M4	Black page	Broken primary corona wire in the cartridge; with the high-voltage supply removed, J601-3 (HV1ON) should fall from +16 V to 0 V one second after the motor starts; check TB603-2 contact with the cartridge primary corona
M5	Stains or repetitive defects	Paper; wrong side of paper; fuser cleaner felt; transfer guide fitted with the roller collar pointing away from the transfer corona; pickup rollers; cartridge; discharging pin contact
M6	Black page with white horizontal stripes	Optical fibre damaged; laser/scanner; laser harness cable; DC controller
M7	Stains on the back of the page	Fuser cleaner felt; clean cassette, transfer guide, transfer corona, fuser and feeder; transfer guide orientation
M8	Dark vertical lines	Fuser cleaner felt; clean the primary corona wire in the cartridge; lines absent from the engine test page means replace the I/O board; transfer corona wire; cartridge
M9	Sharp horizontal black lines	Laser/scanner; laser harness cable; DC controller
M10	Vertical fogged stripes	Clean the mirror under the shutter assembly; primary corona wire; cartridge; all four screws in the high-voltage supply; transfer guide orientation
M11	Horizontal fogged stripes	On the bottom third of the page: replace the paper fuser guide. Otherwise the cartridge, the cleaner felt, then the fuser assembly
M12	Blank spots	Paper type, damp paper, wrong side; Low Toner; refilled cartridge; density dial up
M13	Thin vertical white lines	Rock the cartridge; clean the mirror; clean the transfer corona wire and assembly
M14	Faulty registration	More than 200 sheets; paper; pickup rollers; registration clutch spring; cassette microswitches SW201-SW203; J213-3 (REGD) should rise from 0 V to +5 V three seconds after the motor starts in a service test print
M15	Poor fusing, image smears	Paper; worn fuser rollers; fuser not warming (table D)
M16, M17	Distortion, waviness	LED201 on the DC controller should stay on steadily during a service test print; if it flashes or goes out, replace the laser/scanner, then the laser harness cable, then the DC controller
M18	Uneven density	Rock the cartridge; bent upper transfer guide or transfer guide assembly
M19, M20	Foggy print, horizontal banding	Paper; Low Toner; refilled cartridge; fuser cleaner felt; pickup rollers; density adjustment
M21	Wavy print on grey areas	Low Toner; new cartridge not rocked; refilled cartridge
M22	Blotchy print or ghosting	On the first drum rotation: move the image below 94 mm from the top of the page
M23	IIf or IIg will not print greyscale	Color/Grayscale selected in the Print dialog; at least 5 MB of RAM; refilled cartridge; then the I/O board

High-voltage drive signals

These are measured at high-voltage power supply connector J601 to J601-7 (GND), with the I/O board, cover set, bottom panel and lower cover removed and a cartridge fitted. Each signal should drop to 0 V about one second after the print cycle or main motor starts. If one does not, check the cable to DC controller J211 and then replace the DC controller PCA. If all are correct and the fault remains, replace the high-voltage power supply.

J601 signals before the print cycle

Pin	Signal	Idle level
J601-1	HVTON (transfer corona)	20-24 V
J601-3	HV1ON (primary corona)	+16 V
J601-4	DBAC (developing bias, AC)	16-20 V
J601-6	DBDC (developing bias, DC)	16-20 V

Communication

Tables C1-C6, the printer is not seen or will not print from the computer

Table	Board and port	Checks beyond cables, switches and driver
C1	SC, SCSI	Terminators good; no other device on the same SCSI ID; LaserWriter SC driver installed and chosen
C2, C3	NT/NTX, LocalTalk or RS-232	DIP switches as tabled in Apple's Ports and Cables section; software on the application disk
C4	IIf/IIg, LocalTalk	A second LocalTalk cable plugged into the printer's connector box with nothing on the far end: disconnect it
C5	IIf/IIg, RS-232	A Macintosh connected by RS-232 instead of LocalTalk: use LocalTalk
C6	IIg, Ethernet	A dangling second cable; printer missing from the Chooser on third-party cabling (check termination); network software must support AppleTalk Phase 2

Every communication table ends the same way: try another computer, then a known-good I/O board, and if the fault remains, reseat the interconnect PCA and the DC controller PCA, then replace the interconnect PCA and then the DC controller PCA.

Self-inflicted faults

• Changing the I/O board with the printer switched on. Apple warns this can permanently damage both the printer and the board.
• Wrong SIMMs. The NTX needs 120 ns or faster SIMMs and the IIf and IIg need 80 ns; slower parts cause serious timing problems. Macintosh Plus, SE and II SIMMs do not belong in an NTX, and SC or NTX SIMMs do not belong in a IIf or IIg.
• Switching an NT or NTX from AppleTalk to serial mode while it is on a LocalTalk network. The printer can send serial data onto the network and damage itself and the network.
• Transfer guide refitted the wrong way round. Apple's tables for stains, vertical fogged stripes and back-of-page marks all check that the collar on the roller shaft points away from the transfer corona.
• High-voltage supply refitted without all four Phillips screws, which Apple lists as a cause of vertical fogged stripes.

Related pages

• Apple LaserWriter II General Maintenance
• Apple LaserWriter II SC, Apple LaserWriter II NT, Apple LaserWriter II NTX, Apple LaserWriter IIf, Apple LaserWriter IIg
• LaserWriter II Service Source, Apple LaserWriter Printers Volume I