Apple Personal LaserWriter NT Troubleshooting Guide

Apple's drawings of the Personal LaserWriter's main assemblies, sensors (PS11-PS13, PS501, PS502, PS901) and solenoids (SL501, SL901, SL902)

Fault-finding for the Apple Personal LaserWriter NT and its siblings, the Apple Personal LaserWriter SC, Apple Personal LaserWriter LS, LS/L and Apple Personal LaserWriter NTR, all built on one Canon LBP-LX engine. It follows the Personal LaserWriter tab of Apple's January 1992 Service Guide for LaserWriter Printers, Volume I and the September 1993 addendum, which add the NTR and LS/L. Read Apple Personal LaserWriter NT General Maintenance for the safety rules first: several of Apple's checks are live measurements beside the mains-fed fuser and the high-voltage supply. Apple's method is to swap modules guided by connector readings; its guide has no schematic and no component values.

Before you start

Apple's procedure:

1. Check the set-up and conditions in the pre-power-on checklist below.
2. Learn the safety rules before taking any live reading.
3. For an SC or NT, start at Flowchart 1 and work through each function in turn. For an LS, start at Flowchart 4, then Flowcharts 5 and 6.
4. If a replacement module does not cure the fault, put the original back before going on.
5. After the repair, do the preventive maintenance before returning the printer.

The pre-power-on checklist: line voltage 115 V AC ±10%; a solid, level surface; 10-32.5 °C and 20-80% humidity; not hot, humid, dusty, near flames, in direct sunlight or exposed to ammonia gas; good ventilation; cables and connectors sound; a toner cartridge with toner fitted; the print density dial set correctly; the paper cassette loaded (it is optional on the LS) with paper within specification; the front access door closed.

Status lights

The three lights are on the front access door. On the SC and NT the I/O board runs a self test at switch-on, and the lights then show the printer's state:

SC and NT status lights

Ready	Paper-Out	Paper Jam	Meaning
On	Off	Off	Ready
Off	On	Off	Paper cassette missing or out of paper
Off	Off	On	Paper jam
Off	Off	Off	Front access door open, no toner cartridge, or face-up cover assembly open
Flashing	Off	Off	Test print or engine warming up
Off	Flashing together	Flashing together	Laser assembly, scanner assembly or fuser assembly fault
Off	Flashing alternately	Flashing alternately	I/O board failure
On	On	On	I/O board failure

On the LS the lights show a jam or paper-out only when the printer is driven from a Macintosh with the LS driver.

Engine or I/O board?

Every model has a service test print button on the DC controller PCB, which prints a test pattern from the engine alone and also checks the registration adjustment. On the LS/L the button is reached through the rear panel after taking off its cover. The SC prints a user test page repeatedly at switch-on when its SCSI ID switch is at 7; the NT prints one at every switch-on; the LS prints none.

Apple's SC/NT flowcharts run as follows:

• Flowchart 1, functional check: clear any jam, fit a cartridge, fill the cassette, close the door, switch on and wait 60 seconds, then read the lights. Paper-Out with paper loaded goes to Table F; a jam with no paper jammed to Table K; I/O board failure codes to Table C2 (SC) or C3 (NT); the laser, scanner or fuser code to Flowchart 3. Then switch off, take out the I/O board, switch on, wait 60 seconds and press the service test print button. Paper transport faults go to Table J and print faults to Table H; if the engine prints well but the printer fails with the I/O board refitted, go to Table C2 or C3. Last, print a directory by manual feed from the Macintosh (Table E if manual feed fails).
• Flowchart 2, print engine check: with the I/O board removed, a dead printer goes to Table A (no power) and a motor that does not run to Table D.
• Flowchart 3, print engine error: switch off for three minutes to reset the error, remove the top cover and I/O board, switch on and watch the sides of the front access door. Apple's flowchart then branches to Table B (fuser) or Table G (laser or scanner).

For the LS, Flowchart 4 removes the I/O board and checks power, fuser and motor (Tables A, B, D) and the service test print; Flowchart 5 deals with engine errors, including a check that J209-2 (PFRDV) on the DC controller PCB changes when the test print button is pressed; Flowchart 6 refits the I/O board and connects the Macintosh (Table C1).

NT I/O board codes

To find a failed part on the NT I/O board, switch off, fit Apple's LaserWriter II Test Connector to the 25-pin serial port, switch on and read the lights:

NT I/O board status lights with the test connector fitted

Ready	Paper-Out	Paper Jam	Action
On or off	Flashing	On	Replace RAM SIMM 2
On or off	Flashing	Off	Replace RAM SIMM 1
On or off	Off	Flashing	Replace the ROM SIMM; if two are fitted and the fault stays, replace the other

Before that, Table C3 checks that the rotary switch on the I/O board is at 0, that the LaserWriter and LaserPrep files are in the System Folder and the printer is chosen in the Chooser, and that the LocalTalk or RS-232 cabling is sound. The SC and LS have their own I/O tables (C2 and C1), listed on Apple Personal LaserWriter SC and Apple Personal LaserWriter LS.

Power

Apple's Table A, no power. Take steps 5 to 12 with the I/O shield removed and a toner cartridge fitted.

Table A, no power

Step	Check	Expected	If not
1	AC outlet	Correct mains voltage	Try another outlet
2	Circuit breaker CB1 at the rear of the power supply unit	Plastic shaft not sticking out	Reset it. If it trips again at power-on there is a short to find
3	Power switch SW11, mains cord out and switch disconnected; top pair and bottom pair of terminals	0 Ω switched on, open circuit switched off	Replace SW11
4	J101-1 to J101-2 on the power supply unit	110/115 V (or 220/240 V) AC at power-on	Replace the power supply unit
5	J212-3 on the DC controller PCB to chassis	About +24 V DC	Replace the power supply unit
6	J212-6 to chassis	About +12 V DC	Replace the power supply unit
7	J212-8 to chassis	About +5 V DC	Replace the power supply unit
8	J701 on the density-adjusting PCB	Connected	Reconnect it
9	J701-1 to chassis, at switch-on	About +12 V DC (if present, replace the fan)
10	J701-3 to chassis, at switch-on	About +4 V DC (if present, replace the fan)
11	J701-3 to chassis, test print button pressed	About +2 V DC as the main motor starts (if present, replace the fan)
12	J213-1 on the DC controller PCB to chassis, at switch-on	About +12 V DC: replace the density-adjusting PCB	Replace the DC controller PCB

Fuser

When the fuser fails, the processor on the DC controller PCB cuts the fuser current and charges capacitor C212 to prevent overheating. After replacing the failed module, switch off for three minutes or discharge C212 by hand. Apple's Table B:

1. Unplug J101 from the power supply unit and measure the heater circuit across J101-1 and J101-2 on the cable connector. Expect under 10 Ω. If not, check the cable, then replace the fuser heater bulb.
2. Check that J209 on the DC controller PCB is making good contact.
3. Let the fuser cool, remove it and measure the thermistor across J502-1 and J502-3 on the fuser assembly. Expect 180-290 kΩ at room temperature. If not, replace the fuser assembly, then check the cable from J502 to J209.
4. Refit the fuser, close the door, remove the I/O shield and watch J212-9 (FSRDRV) on the DC controller PCB at switch-on. It should swing between +5 V and 0 V as the heater bulb switches on and off. If not, replace the DC controller PCB.
5. Switch off for three minutes to cool, then check for 110/115 V (or 220/240 V) across J101-1 and J101-2 on the power supply unit at switch-on. Absent: replace the power supply unit. Present: replace the fuser assembly.

An NT that prints only on the top half of the page and leaves the bottom half blank needs a new fuser bulb or fuser assembly. On an NTR the same symptom calls for the version 4.0 ROMs (kit 076-0685).

Motor, sensors and laser

Tables D to G

Symptom	Table	Checks and expected readings
Main motor does not turn	D	Toner cartridge fitted; J209 and J210 seated; open and close the face-up cover (its lever must reach the arm of face-up cover sensor PS502); obstructions in the drive or feeder gear train; J213-4 to chassis about +3.4 V DC with the door shut and a cartridge in (else check the wiring to J12 and the toner cartridge sensor PS11); J209-8 about +3.4 V (else PS502 or the multipurpose cable); main motor coils on the unplugged J210 connector, pins 1-2, 1-3, 4-5 and 4-6, about 13 Ω each. Coils good: replace the DC controller PCB; otherwise the motor.
Manual feed fails	E	J209 seated; J209-2 (PFRDV) to chassis falls from about +24 V to 0 V when the test print button is pressed with paper on the multipurpose tray. Falls: replace the multipurpose cable assembly. Does not: DC controller PCB.
Paper-Out lit with paper loaded	F	Cassette filled and seated; paper-out sensor arm free and undamaged; J205-6 (OPPOUT) toggles from +5 V (cassette in) to 0 V (cassette out). No toggle: cassette paper sensor PS901 on the cassette feeder. Toggles: DC controller PCB.
Laser or scanner fault	G	With the I/O shield off and a cartridge fitted: optical fibre cable J204 connected; with J207-6 (LPC) jumpered to chassis and the printer switched on, J202-4 (LSRPWR) to J202-2 between 1.5 and 2 V DC after one second (else DC controller PCB), and J202-3 (APCIN) falling to about +1.5 V within five seconds (else laser assembly); J301 on the scanner and J203 connected; with the jumper removed, J203-2 to J203-6 between +11 and +12 V (else check J202-6 to J212-5 and the power supply unit); J203-3 (SCNON) falling from about +4 V to 0 V when the test print button is pressed (falls: scanner assembly; does not: cable, then DC controller PCB).

Print quality

Apple's chart sends each defect to a table, H1 to H13. The high-voltage readings are taken on J206 of the DC controller PCB, to chassis, while a service test print is running, with the top cover, I/O board and I/O shield removed and a cartridge fitted.

Print quality tables

Defect	Table	Checks
Light image	H1	Print density lever; rock the cartridge; fresh paper; new transfer roller; the left transfer roller mount spring touching the high-voltage contact when the door closes; FT101 seated on the high-voltage contact assembly. Within five seconds of the pickup roller turning: J206-7 (HVT1) about 0 V, J206-9 (HVT2) about +3.2 V, J206-10 (HVT3) about 0 V (any wrong: DC controller PCB). J206-8 (HVD) falling from about 7 V to 0 V two seconds after pickup starts (falls: high-voltage power supply; does not: DC controller PCB).
Dark image	H2	Density lever; clean the grounding plate contact of the high-voltage contact assembly; high-voltage contacts touching the cartridge; J206-3 (HVAC) falling from about +4.5 V to 0 V when the main motor starts (falls: high-voltage supply; does not: DC controller PCB).
All-blank print	H3	Sealing tape removed; new cartridge; high-voltage contacts; J206-3 (HVAC) as for H2; J206-8 (HVD) as for H1.
All-black print	H4	New cartridge; J206-6 (HVDC) falling from about +8.2 V to 0 V when the main motor starts (falls: high-voltage supply; does not: DC controller PCB).
Large dots in vertical lines	H5	Dirty static charge eliminator on the fuser; the Cleaning Page; transfer roller (clean with a dry lint-free cloth or replace).
Stains on the back of the paper	H6	Transfer roller; cassette entrance guide; feeder rollers (slightly damp cloth); fuser rollers (Cleaning Page).
Dark vertical lines	H7	Lines on the drum during a test print (cartridge); dirty fuser rollers; damaged fuser.
Smudged vertical bands	H8	Cartridge; fuser rollers; static charge eliminator.
Smudged horizontal bands	H9	Fuser rollers; bands at regular intervals on a test print mean the cartridge, otherwise the fuser assembly.
Blank spots	H10	Damp paper; cartridge; transfer roller.
Solid white vertical lines	H11	Rock the cartridge; streaks on the drum (cartridge); foreign material at the laser outlet in the chassis or the beam slot in the cartridge; dirt on the lens assembly (replace the lens assembly).
Faulty registration	H12	Overfilled cassette or tray; paper; the registration adjustment; pickup unit sensor arm; J208-1 (PFSNS) falling from +5 V to 0 V as paper passes PS13 (does not: PS13; does: DC controller PCB).
Poor fusing	H13	Clean the transfer roller; if the tenth of ten test prints is lighter than the first, replace the fuser; dirty lower fuser roller; paper choice; otherwise the fuser assembly.

The registration procedure (VR201, 3.6 mm) is on Apple Personal LaserWriter NT General Maintenance#Registration adjustment.

Paper transport

Open the front access door to see where the paper stops, then go to the matching table.

Tables J1 to J6 and K

Fault	Table	Checks and expected readings
No pickup from the cassette	J1	J205 seated; J208-1 (PFSNS) +5 V at switch-on (else PS13 on the feeder assembly); TB703-1 on the density-adjusting PCB +5 V (else PS12, the delivery unit paper sensor); J205-7 (OPMD) briefly rising from 0 V to 1.4 V a minute after switch-on when the test print button is pressed (else DC controller PCB); cassette feed roller clutch solenoid SL902 about 0.22 Ω across J902-4 and J902-5; J205-8 (OPCD) briefly rising from 0 V to 1.4 V; cassette pickup roller clutch solenoid SL901 about 0.124 Ω across J902-6 and J902-7.
No pickup from the multipurpose tray	J2	J209 seated; PS13 and PS12 checks as J1; J209-2 (PFRDV) briefly falling from about +24 V to 0 V on a test print (falls: multipurpose cable assembly; does not: DC controller PCB).
Jams in the pickup area	J3	Paper; overfilled tray; worn or deformed pickup rollers; the large black gear turning the pickup roller freely; J209-2 as J2; cassette seating and fill; worn cassette pickup and feed rollers; cassette pressure plate springs; pickup unit sensor arm; J208-1 to J208-2 falling from +5 V to 0 V as paper passes PS13.
Jams in the fuser or delivery area	J4	Delivery unit sensor arm on the fuser; dirty lower fuser roller (Cleaning Page); fuser rollers turning freely; the three white gears by J502 on the front door turning the delivery rollers; paper deflector position; worn face-down or face-up delivery rollers; PS13 as J3; J213-5 (POSNS) to J213-9 falling from +5 V to 0 V as paper passes PS12.
Sheets stuck together	J5	Paper; worn separation pad; paper under the cassette hold-down brackets; damaged brackets.
Wrinkles	J6	Paper; wrinkling as paper passes the feeder (clean or replace the cassette pickup and feed rollers); dirty lower fuser roller; otherwise the fuser assembly.
Jam light with no jam	K	Paper fragments; delivery unit sensor arm; pickup unit sensor arm; PS13 and PS12 signal checks as J4.

Related pages

• Apple Personal LaserWriter NT General Maintenance
• Apple Personal LaserWriter NT, Apple Personal LaserWriter SC, Apple Personal LaserWriter LS, Apple Personal LaserWriter NTR
• Apple LaserWriter Printers Volume I
• Service Training Personal Laserwriter Sc Nt Ls Service Course Version 1.1 1996