Apple Personal LaserWriter 320 Troubleshooting Guide

Apple's drawing of the Personal LaserWriter 320 controller assembly board, with the paper sensors PS301-PS304, the fuses and the HVT connector assembly

Fault-finding for the Apple Personal LaserWriter 320, from chapter 4 of Apple's July 1995 Service Guide: LaserWriter Printers, Volume III. The same chapter covers the LaserWriter 4/600 PS on the same Canon P90 engine, and the 320's engine parts also carry the Apple Personal LaserWriter 300's part numbers, so most of the engine tables apply to all three. Read the safety section of Apple Personal LaserWriter 320 General Maintenance first. Apple's procedure is module exchange: every table ends in a replacement part, and the guide has no schematic or component values.

Before you start

Apple's pre-power-on checklist: line voltage 115 V AC ±10%; a solid, level surface; 10-32.5 °C and 20-80% humidity; away from heat, damp, dust, flames, direct sunlight and ammonia; good ventilation; cables and connectors sound; a toner cartridge with toner; the cassette loaded with paper within specification; the top access door and the rear door assembly closed.

Retry the printer after every change. If a replacement module does not cure the fault, refit the original before the next step. After a repair, do any preventive maintenance needed before returning the printer.

Status LEDs, self test and diagnostics

At power-on all three LEDs light. Ready/In Use goes out when the I/O controller board passes, Paper-Out when the RAM card passes, and Paper-Jam when the engine passes. In use, Ready/In Use is steady on standby and flashes during a job, Paper-Out is steady when the cassette is empty in cassette-feed mode, and Paper-Jam is steady when paper is jammed.

For a fault on the I/O board or the engine, use the built-in diagnostic: switch off, fit Apple's serial loopback cable (077-8265) to the serial connector on the I/O board and switch on. Allow up to 90 seconds. The LED pattern then names the module: controller assembly (Paper-Jam), RAM card (Paper-Out), fuser assembly (Ready/In Use), fan motor (Paper-Out and Paper-Jam), laser assembly (Ready/In Use and Paper-Jam), or another engine fault (Ready/In Use and Paper-Out). The full table is on Apple Personal LaserWriter 320#Status LEDs and self test.

Service test page

The service test page is a series of vertical lines printed by the controller assembly alone. If a fault appears only when printing from the Macintosh, and never on a service test page, the engine is working and the I/O board or the host side is at fault.

1. Remove the printer cover.
2. Fit a toner cartridge and fill the paper cassette. Fit the cartridge before plugging in: Apple lists plugging in without one as a cause of jams and of failure to pick up paper.
3. Plug in and switch on the printer.
4. Defeat the paper delivery sensor PS301 with a folded piece of paper. Push it in only until it touches the metal shaft of the fuser; if it goes too far the sensor stays open and the printer reports a jam.
5. Cover the toner cartridge with a sheet of paper to keep light off the drum.
6. Hold down the toner cartridge and the cover interlock actuator, and press the service test page button with a screwdriver.

When the interlock actuator is held down the fan should run and the delivery rollers turn. If the fan does not start, check that PS301 is properly defeated, the actuator is fully down and the cassette is fitted. If the cartridge is not held down firmly, the page may come out blank because the cartridge is not touching the HVT connector.

The four paper sensors on the controller assembly are PS301 (paper delivery, in the fuser path), PS302 (registration, which also senses paper in the manual slot and misfeeds), PS303 (winding, between the drum and the fuser) and PS304 (cassette empty). A sheet that does not reach PS301 or PS303 in time is reported as a jam; one that does not reach PS302 in time is a pickup delay jam.

Apple's flowchart

Apple's print engine check starts with a Macintosh running the LaserWriter 8 driver. Connect it, clear any jam, fit a cartridge, fill the cassette, switch on and plug in the printer. A fan that does not run goes to Table 81, a motor that does not run to Table 82. Then print a window or the desktop: follow any error message on the screen, and go to the print-quality chart for a poor page. Without a working Macintosh, remove the cover and I/O board, set up for a service test page as above, and use the same tables, with paper transport faults going to Tables 83 to 86.

Power and engine

Tables 81 to 86

Fault	Table	Apple's checks, in order
Fan does not run	81	With a cartridge fitted, unplug the printer and, "because of the possibility of a capacitor error", wait 4 minutes before plugging it in again; cover seated and rear door closed (or interlock held and PS301 defeated); correct outlet voltage; power cord; fan cable connected at the laser/scanner assembly and not pinched under the tab that holds the fan; J804-3 (FANON) to J804-1 (+12VGND) on the laser/scanner assembly changing from 0 V to about 12 V DC when the printer is plugged in (if so, replace the fan); fuse FU101 on the controller assembly (if blown, replace it; if not, replace the controller assembly).
Main motor does not turn	82	Motor seated against the controller assembly; then the motor, then the controller assembly.
No pickup from the cassette	83	Cassette chosen in the Print dialog; cartridge fitted before the printer was plugged in; known-good paper; cassette not overfilled; paper pickup roller worn or deformed; pickup solenoid; fuser assembly seated against the controller assembly; with the fuser removed, about 440 kΩ across J204-1 and J204-2 (else replace the fuser); continuity across J103-1 and J103-2 (else replace the fuser); then the controller assembly and pickup motor.
No pickup from manual feed	84	Manual feed chosen in the Print dialog; known-good paper; slot not overfilled; arm registration assembly broken; then pickup motor, controller assembly and fuser assembly.
Jams in the pickup or transfer area	85	Known-good paper; cartridge fitted before plugging in; wrinkled or damaged paper (look for obstructions and misfitted feed parts); arm registration assembly; the winding paper sensor on the feeder guide assembly (replace the feeder guide assembly); a jam on a service test page means the fuser assembly, otherwise the pickup motor and then the controller assembly.
Jams in the fuser or delivery area	86	Known-good paper; obstructions; winding paper sensor; delivery roller assembly and passive delivery rollers fitted and working; paper delivery selector moving freely (else the rear door assembly); a jammed or broken paper delivery sensor in the fuser (replace the fuser assembly), otherwise the controller assembly and then the fuser.

Print quality

Tables 87 to 103

Defect	Table	Apple's checks
All-blank page	87	Sealing tape removed; with the cover off, the cartridge pressed onto the HVT connector; dirty metal contacts on the cartridge or HVT connector assembly (clean with a soft, dry cloth); then the controller assembly and the laser/scanner.
All-black page	88	A known-good controller assembly; if the fault stays, the laser/scanner assembly.
Uniformly light or faded	89	Rock the cartridge; raise the print density under Options in the Print dialog and print about a dozen pages; known-good cartridge; dirty contacts; then the transfer roller, HVT connector assembly, controller assembly and laser/scanner.
Uniformly dark	90	Print density; dirty contacts; then the controller assembly and laser/scanner.
Sharp black vertical lines	91	Known-good cartridge; only from the Macintosh, never on a test page, means the I/O board; otherwise the fuser assembly, then the laser/scanner.
Sharp white vertical lines	92	An obstruction by the laser opening shadowing the drum; Macintosh-only means the I/O board; otherwise the pickup motor, laser/scanner and mirror assembly.
Irregular black lines	93	Replace the toner cartridge.
Stairstepping, jagged or shaky vertical lines	94	Laser/scanner seated on the scanner interconnect assembly; interconnect seated on the controller assembly; absent from a test page means the I/O board; otherwise the laser/scanner, then the controller assembly.
Evenly spaced smudged horizontal bands	95	Interrupt a print and look at the drum: marks on the drum mean the cartridge, a clean drum means the fuser assembly.
Sharp black horizontal lines	96	On normal prints but never on a test page: I/O board. Otherwise the fuser assembly, then the laser/scanner.
Bad registration	97	Known-good paper; overfilled cassette or slot; the registration adjustment; then clean or replace the pickup roller, the pickup motor, a broken arm registration assembly and the controller assembly.
Skewed print	98	The mirror adjustment.
Bad fusing	99	Known-good paper; overfilled cassette or slot; the registration adjustment; then clean or replace the transfer roller and replace the fuser assembly.
Toner on the back of the page	100	Clean the transfer roller with a dry, lint-free cloth only (replace it if it will not come clean); clean the transfer guide assembly and the feeder guide assembly; then the fuser assembly.
Blank spots	101	Dry, known-good paper; clean the transfer roller; then the fuser assembly and the transfer roller.
No PhotoGrade	102	Fit the 6 MB RAM card: PhotoGrade needs 8 MB.
Legal page not printed edge to edge	103	Fit the 2 MB RAM card: edge-to-edge legal printing needs 4 MB.

The mirror and registration procedures are on Apple Personal LaserWriter 320 General Maintenance.

Things that are not faults

• A light or patchy page after the cartridge has been out in room light. More than five minutes of light can damage the drum; a cartridge left in a dark drawer for several hours may recover.
• A blank service test page with the cover off, when the cartridge was not held down onto the HVT connector.
• No PhotoGrade, or a legal page with margins, on a 320 with 2 MB of memory (Tables 102 and 103).

Related pages

• Apple Personal LaserWriter 320 General Maintenance
• Apple Personal LaserWriter 320
• Apple Personal LaserWriter 300, whose page carries Apple's 1993 tables for the same engine