Apple LaserWriter 8500 Troubleshooting Guide

The LaserWriter 8500 in its basic configuration (Apple Service Source).

Fault-finding for the Apple LaserWriter 8500, from Apple's Service Source for the printer and its user's guide. The printer reports faults on four status lights: Paper Jam, Paper Out, Toner and Ready, with Ready at the front. The I/O controller board drives them from the engine's sensors, and the same lights carry the power-on self test (POST) and the technician's extended self test (EPOST). Maintenance is on Apple LaserWriter 8500 General Maintenance.

The fixing rollers run at about 400 °F (200 °C). Apple's user's guide says to let them cool for about 40 minutes before maintenance or troubleshooting, and the Service Source says to let the fuser cool before removing it. The high-voltage power supply feeds the charge and magnetic rollers in the toner cartridge, the transfer roller and the detack saw; Apple gives no voltages.

Start-up and POST

At switch-on all four lights come on briefly, go out and come on again: that marks the start of POST. POST checks three stages in order: the I/O controller's ROM and SIMMs, the rest of the I/O controller, and the DC controller board. It puts the lights out from front to back as each stage passes. If a stage fails, the Paper Out and Paper Jam lights flash alternately for ever. Note how many lights had gone out first: if only Ready had gone out, the failure was in stage two and the I/O board is at fault. Apple's text says both that POST runs in the first 10 seconds of start-up and that the testing takes about 40 seconds; the printer is ready after about 50 seconds.

Once POST has passed, the PostScript code takes over. The Ready light can stay on for up to 15 seconds before a PostScript fault shows, so wait before switching off.

Status lights after POST (Service Source and user's guide)

Lights	Meaning
Ready on	Ready, about 50 seconds after switch-on
Ready flashing	Warming up, printing the startup page or processing a job. If it flashes for ever, switch off, disconnect the printer from the network and restart; if the flashing stops, look at the network or the host software
Ready flashing two colours	Point-of-sale demonstration mode. The Service Source says two shades of green, the user's guide amber and green. Hold Ready while switching on to leave it
Paper Out and Paper Jam flashing alternately	POST error (see above). After a memory upgrade, check that the SIMM is seated and the layout is supported
All off	Top cover or fuser access cover open
Paper Out on	No paper, or no cassette
Paper Out flashing	Waiting for a manual-feed sheet
Paper Jam on	Paper jammed
Paper Jam flashing	The user's guide says the printer needs service; the Service Source chart does not list it
Toner on	Toner low
Toner flashing	Toner cartridge not fitted
All four on	The user's guide says the printer needs service

EPOST

EPOST tests the same three areas as POST, more thoroughly, and uses different light codes. It needs Apple's printer loopback test plug, 922-1489, which is bright green. Apple's older black plug does nothing on this printer. Switch off, fit the plug to the LocalTalk port on the back of the I/O controller board and switch on. If EPOST finds no fault it prints an EPOST test page and hands over to PostScript. If it finds one, the lights go out and then repeat a cycle until the printer is switched off: all on for a second, all off for a second, the error code for a second, all off for two seconds.

EPOST error codes (Service Source, Troubleshooting p. 7)

Lights	Slow flashing	Fast flashing
Paper Jam	I/O controller board	Fuser
Paper Out	ROM	Laser/scanner
Paper Jam and Paper Out	General SIMM error	Fan
Toner	General memory error	Miscellaneous engine error
Toner and Paper Jam	SCSI disk	Duplexer
Toner and Paper Out	DC controller board	Toner cartridge missing
Top three lights		Toner cartridge empty

A miscellaneous engine error covers paper jams, an open cover, a missing cassette, no paper or an open duplexer. Apple's note: check for a jam first, because EPOST often picks a sheet for its test print, and after a restart it reports the jam before anything else.

Service test page

The service test page is held in firmware on the DC controller board, so a good one proves the engine. If a print fault on a normal page also appears on the service test page, the I/O controller board is not the cause and should not be swapped. With the I/O board fitted, press the test page button with a paper clip through the small unmarked hole at the top of the I/O bracket. With the I/O board and shield out, jumper the two pins of connector P23 on the DC controller board.

Apple's flowcharts

Apple's starting point is a basic set-up: remove the duplexer and any sheet feeders, load paper and push the cassette fully in, fit a known-good toner cartridge, close all covers, switch on, and make sure the startup page is turned on in the Printer Utility. Then work down the questions; a "no" leads to the flowchart shown.

Flowchart 1: starting point

Check	If not
A. Does the fan come on at switch-on?	Flowchart 2
B. Do the delivery rollers turn?	Flowchart 3
C. Does the printer come ready?	No lights: flowchart 4. Jam light: flowchart 5. Paper Out light: flowchart 6. Toner light: flowchart 7. Paper Out and Paper Jam flashing: run EPOST
Does it deliver a startup page?	Flowchart 8
Is the print quality right?	Image defects, below

Flowcharts 2 to 8

Flowchart	Symptom	Apple's checks
2	Fan does not come on	If it started after a repair, check J3 on the I/O board, then J122 on the power supply. Otherwise check the mains voltage and that the printer's 110 V or 220 V rating matches it; if the fault stays, replace the power supply
3	No drive to the delivery rollers	After a repair, check main motor connector J16 on the DC controller board. Otherwise check that all covers are closed and a cartridge is fitted, and look at the fuser idler gear, fuser guide lever and main gear assembly
4	No lights at all	This is the cover-open state, sensed by the fuser cover and top cover interlock switches. After a repair, check the I/O board to status panel cable, the two-pin cable into the top of the duplex interface board and J21 on the DC controller board. If the printer otherwise works, replace the status panel or its cable. If not, check that both covers are shut, the plastic tab on the fuser access cover and the white nylon tip of the actuator rod in the top cover, then the switches, cables and boards
5	Jam light on at start-up	Only the exit sensor and the registration sensor report a jam at start-up. See the exit actuator by opening the fuser access cover and looking down the slot in the top of the fuser, about midway; see the registration actuator by removing the cartridge and looking through the acetate window above the manual feed pickup rollers. Clear any paper or scraps. If there are none, a broken actuator has the same effect as paper: inspect both actuators, sensors and their cables
6	Paper Out on at start-up	Take the cassette out, push the paper-present actuator up with one hand and press one of the four microswitch actuators at the left front of the opening with the other. If Ready comes on, the cassette is at fault (bottom plate not rising, or the cam actuators on its side). If not, after a repair check P/J20 on the DC controller and the cassette feeder board and paper-present sensor cables; otherwise inspect the actuators, then suspect the cassette feeder board (922-2770) or left cassette guide assembly (922-2773)
7	Toner light on at start-up	Flashing means no cartridge: the cartridge sensor assembly (922-2811) in the top cover presses a small tab on the cartridge. Check the tab and the sensor, and P/J17 on the DC controller. Steady means toner low, sensed magnetically by the toner sensor (922-2799, also part of manual feed sensor assembly 922-2796); after a repair check P/J22 on the DC controller and the coupling on the sensor cable
8	Ready, but no startup page	If no paper is jammed and the pickup rollers turned, the fault is mechanical: a misaligned or damaged pickup roller, or the cassette. If they did not turn, run a service test page. If it feeds, check the startup page is turned on, then replace the I/O board. If it does not, the I/O board is not at fault; if the multipurpose tray feeds from a host, the DC controller is not either. Check P/J20 and the cassette feeder board cables, then the cassette feed solenoid and feeder board

For jams in flowchart 8, Apple's order is: after a repair, the connections at the turn and registration clutches, and any grinding from a misassembled paper handling gear assembly, main gear assembly or clutches; a jam at the fuser can mean the fuser is not fully seated or the fuser guide lever is damaged. Otherwise check the paper and the path, then compare the multipurpose tray with the cassette (cassette or its pickup), long-edge with short-edge feed (registration or cassette size sensing), a service page with a host job (I/O board), and different places or times of day (temperature or humidity).

Paper jams

From the user's guide:

1. Open the back door of the printer and pull out any paper there.
2. Open the top cover and take out the toner cartridge. Remove paper from around the pressure roller. Refit the cartridge and close the cover.
3. Pull out the cassette and remove any paper there. Paper with an edge over the bracket at the front of the cassette is reported as a jam.
4. Check the exit area on top of the printer.
5. On a 500-sheet feeder, check its back door and its cassette. On the duplexer, check its top door and its lower back door.

Open and close the top cover to reset the printer after clearing a jam, except when only the duplexer's doors were opened. If jams start after setting up, check that all the packing material is out. Fan the paper before loading, do not overfill the cassette, and feed stiff stock from the multipurpose tray, which has a straighter path.

Image defects

Apple's tables assume a known-good toner cartridge has already been tried.

Image defects (Service Source, Troubleshooting pp. 17-32)

No.	Defect	Apple's checks
1	Blank page	Laser beam not reaching the drum. Look for the cartridge's sealing tape left in or something outside the laser/scanner. If only one job does it, check settings such as magnification. Then run EPOST
2	Black page	A uniform charge on the drum, either from the document (a black mask visible only in preview) or a charging or exposure fault. Run EPOST, then a service test page: if the fault goes, suspect the I/O board. If neither finds it, replace the high-voltage power supply
3	Light or faded	Too little charge. Check the paper and the density settings. After a repair, check connector TR into the bottom of the high-voltage power supply and its orientation. Otherwise suspect the transfer roller or the high-voltage power supply
4	Dark image or background	Too much charge, or poor grounding of the transport chute or fuser. Check the paper and density settings
5	Black vertical lines	Service test page: if the lines go, the I/O board; if not, the fuser or laser/scanner
6	White vertical lines	Something, such as a hair, in the laser beam. Service test page: if the lines go, the I/O board; if not, probably the laser/scanner
7	Black horizontal lines	Service test page: if the lines go, the I/O board; if not, probably the laser/scanner
8	Skew	If printing from the multipurpose tray cures it, the cassette: take off its bottom cover and check the small white pinion gear between the two toothed width racks, and replace it if damaged. If both sources skew, check the paper
9	Poor fusing	Run EPOST, then check the connections to the fuser. If they are good, the fuser or the power supply
10	Blank spots	Paper or environment out of specification
11	Repeating marks	Almost always dirty rollers. Stop a print midway and look at the paper and drum: if the mark is there, it is before the cartridge (registration, feed or pickup rollers); if not, the fuser
12	Wrong orientation	The cassette senses orientation and the multipurpose tray does not. Set the tray's default in the Printer Utility to print short-edge feed from it
13	No duplexing	Check the driver and that two-sided printing is selected. Duplex printing needs more memory for some paper sizes and with PhotoGrade; with too little, pages print one-sided
14	Black page with streaks, or a ghost of the same area further down	Usually a brand-new cartridge. Lower the print density: lift the front hood, find the dial with the crescendo mark on the left inside the printer and turn it towards the outside of the printer; then move the Print Density slider in the Apple Printer Utility to the left and click Send

The user's guide adds some user-level remedies: for light print, white voids or streaks, rock the cartridge gently to spread the toner, darken the density setting or change the cartridge; toner smudges after a jam, or after printing on paper smaller than the page, usually clear after a few letter-size pages; blotches or ghosts on the first copy often go after two or three more copies, because they come from the first turn of the drum; curling paper may be damp or too heavy (16-24 lb for the cassette, 16-32 lb for manual feed).

Parts named in the procedures

Parts and connectors (Service Source)

Item	Part number or connector
Printer loopback test plug (green)	922-1489
I/O controller board	661-1420
DC controller board	922-3092
Power supply	922-3031 (110 V), 922-3032 (220 V)
High-voltage power supply	922-3094
Fuser assembly	661-1418 (110 V), 661-1423 (220 V)
Fuser heater	922-2804 (110 V), 922-2820 (220 V)
Laser/scanner assembly	922-3093
Transfer roller	922-2800
Status panel assembly	922-2767
Cartridge sensor assembly	922-2811
Toner sensor assembly; manual feed sensor assembly	922-2799; 922-2796
Cassette feeder board; left cassette guide assembly	922-2770; 922-2773
Fan	922-2814
Connectors named in the flowcharts	J3 (I/O board); J122 (power supply); J16, J17, J20, J21, J22 and P23 (DC controller board)

Related pages

• Apple LaserWriter 8500
• Apple LaserWriter 8500 General Maintenance
• Apple LaserWriter 8500 Documentation
• Apple LaserWriter 12/640 PS Troubleshooting Guide