Apple Color LaserWriter 12/600 PS Troubleshooting Guide

Color LaserWriter 12/600 PS (photo: Hellisp, All About Apple museum, CC BY-SA 3.0)

Fault-finding for the Apple Color LaserWriter 12/600 PS and the Apple Color LaserWriter 12/660 PS, from the troubleshooting chapter of Apple's Service Source for both printers and the 1995 Service Guide. Read the safety section first: the printer has a laser, a high-voltage supply and a fuser that takes at least five minutes to cool.

Before you start

Apple's checklist begins with the printer's position: it must stand on a flat, sturdy and perfectly level surface, away from vibration and sunlight, because an out-of-level printer gives oil overflow errors. Then check that the photoconductor and toner disposal box are fitted and the disposal box cover lowered, that each toner cartridge's inner housing is locked so it cannot turn, that the sealing tape is off each cartridge and that each is in its own bay.

Apple's required tools are a PowerBook with AppleTalk connectors, the Color LaserWriter Service Utility and its diagnostic interface cable (922-1703), a digital multimeter, Phillips and flat-blade screwdrivers (magnetised recommended), needle-nose pliers, cotton gloves for the transfer drum, the fuser oil extraction syringe, lint-free paper or cloth and the photoconductor tray; it also recommends a vacuum made for xerographic copiers, a magnifying loupe and a dental mirror for the oil-overflow sensor. The Service Utility, on the Service Source Companion CD, uploads and downloads printer parameters through the I/O test connector J109 on the DC controller board.

Running it with the covers off

To watch the engine work, remove the top, left, rear and fuser access covers and the rear shield plate, with all consumables fitted, the front and pickup doors shut and the separation discharge assembly down. Defeat the fuser cover interlock by wedging the green cleaning brush tool between the chassis and the actuator plate, and plug in. The door switch is pressed only when all three doors are closed, and it removes +24 VA from the drive loads when any of them opens. Mains, the laser and the fuser are all live in this state.

Power-on self-test

At switch-on all 21 status panel lights come on briefly. POST then tests the I/O controller (processor and SIMMs), the rest of the I/O controller, the print engine and optional hardware, putting out the four primary lights one by one; a good printer passes in about 40 seconds. A failure leaves the paper-out and paper-jam lights flashing indefinitely, with the toner and maintenance lights showing which test failed. The POST codes matrix (Service Source p. 175; Service Guide Figure 30) maps each light pattern to the I/O controller board, RAM SIMM 1 (J11) or 2 (J10), the hard disk, the ROM checksum, the fuser assembly, fuser oil pump, temperature and humidity sensor, paper pickup block, calibration density sensor, DC controller board, power supply, toner carousel, laser/scanner, main and drum motors and the three fans. Apple stresses that a code names a functional path, not necessarily a faulty module.

All four primary lights flashing means an error that POST could not detect in time: Apple names the laser/scanner, some fuser errors and some carousel errors. Restart the printer under extended POST (EPOST) to identify it, using the bright green loopback test plug (922-1489) in the LocalTalk port with the I/O board's configuration switch to the right. The older black test plug does not work on this printer.

Selected POST code notes (Service Source, pp. 178-182)

Error	Apple's checks, in order
I/O controller board	Check that the controller and interconnect boards are seated and the cable from J802 (interconnect) to J108 (DC controller) is secure; tighten the two screws on the I/O bracket; replace the I/O controller board (rarely the interconnect board)
RAM SIMM	Check the SIMMs are seated in the correct sockets in a supported configuration; replace the SIMM
Hard drive	Drive present but failing: check the cable; replace the drive
Fuser assembly (heater circuit)	If the fuser was just replaced, check it is the correct voltage and its two captive screws are tight. Watch whether the fuser bulbs glow during warm-up: if they do, the thermistor in the fuser is the likely fault (replace the fuser). If not, check J1 (4-pin black and white) and J2 (9-pin yellow) at the power supply, then remove the fuser and check continuity between pins 1 and 2 and between pins 3 and 4 on its connector; an open circuit means a new fuser, continuity means a new power supply
Fuser oil pump (oil overflow)	See the oil overflow section below
Temperature and humidity sensor	Check the transit coupling and J2005 on the mechanical controller; replace the sensor
Paper pickup block	Check the cassette pickup assembly mates firmly and J2002 is connected; replace the cassette pickup board (922-1311), then the pickup assembly
Calibration density sensor	Check the black arm of the density sensing assembly is attached to the top access door and the assembly can pivot down above the transfer drum; check the ribbon at J103; replace the density sensing assembly
DC controller	Replace the DC controller board (661-0898)
Toner carousel	Usually a jammed carousel or wrongly installed cartridges on a new printer. Check that the carousel knob turns it, clear blockages, check the carousel interlock, reconnect J2006 and J2016, check the carousel position sensor
Laser/scanner	Check J102, J110 and J111 on the DC controller and the laser/scanner connectors; replace the laser/scanner assembly
Main motor; drum motor	Reseat J2013 (main) or J2015 (drum) on the mechanical controller; replace the main motor or the printer drive assembly
I/O controller fan; fuser fan; main fan	Reseat J2010, J2012 or J2019 on the mechanical controller; replace the fan

Always check the ribbon cable between J2007 on the mechanical controller and J112 on the DC controller: Apple says a poor connection there causes unpredictable behaviour.

Fuser errors

The fuser has three protections. Error A: the DC controller sees an abnormal thermistor reading, or the fuser fails to warm on time (for example, not reaching 40 °C within 130 seconds, or each further 20 °C step within 80 seconds), and cuts the heaters. Error B: the safety circuit cuts the heaters when the thermistor reads above 217 °C, and the processor reports a power supply error. Error C: a thermoswitch opens at about 230 °C. After a fuser heater error, the DC controller keeps the heaters off if the printer is switched on again within 30 minutes, so a quick restart does not clear it.

Oil overflow

The oil-overflow sensor PS10 is a photo-interrupter with a float that rises when oil fills the overflow pan. Apple's order of checks:

1. If the error appeared straight after service, reseat J2009 on the mechanical controller, routing it through the cable guides.
2. If the printer has just been moved or tilted, oil may have contaminated the sensor: replace the photo-interrupter (922-1353).
3. Open the fuser access door, lower the delivery roller and look at the float (a dental mirror against the lower fuser roller gives a clear view). If the float is up, the pan is filling: replace the fuser, extracting the oil from both the reservoir and the overflow well first. If not, replace the fuser, then the fuser interconnect cable.
4. If the error keeps returning, level the printer with the level and shim kit (076-0622).

Apple's 1996 bulletin adds a field fix: with the fuser cooled, pump the green fuser jam release lever at least 50 times to move oil from the fuser's oil catch tray back to the reservoir, then push the float down gently to its normal position through the fuser delivery door.

No power

Check the line voltage and the plug. The power supply has a circuit breaker: look through the small cutout above the power inlet. To reset it, remove the rear cover and move the yellow indicator to the right with a non-conductive probe (a toothpick or pen cap) until it disappears. If it trips again, check for a short on the AC side, then replace the power supply. If the fault followed reassembly, check the connectors on both sides of the transit coupling behind the supply, J4 and J6 on the supply, and J101 on the DC controller, which carries the power-on and power-off signals.

Flowchart summary

Apple's flowcharts (Service Source, pp. 185-190)

Symptom	Apple's direction
Nothing at all	Flowchart B: line voltage, circuit breaker, connectors
Power but never ready; all 21 lights stay on	I/O controller board not installed or failing: reseat it into the interconnect board, then replace it
Secondary lights on	Fuser light: the cleaning belt sensor has tripped and 500 prints remain before the fuser must be replaced. Oil light: 50 prints remain before the oil bottle must be replaced
Ready but no startup page	The startup page may be disabled in the Apple Printer Utility
Startup page prints but host jobs fail	Print a Finder window from a PowerBook connected directly; if that works the fault is in the network or host software

Print quality

Repeating defects by roller (Service Source, p. 171)

Roller	Interval on page	Possible defect
Upper fuser roller	134 mm (5.27 in)	Tracking on the front of the page
Lower fuser roller	134 mm (5.27 in)	Tracking on the back of the page
Photosensitive drum	129 mm (5.07 in)	Tracking on the front
Developing cylinder	50 mm (1.96 in)	Blank spots or tracking on the front
Primary charging roller	38 mm (1.49 in)	Blank spots or tracking on the front
Attraction roller	50 mm (1.96 in)	Tracking on the front or back
Discharge roller	50 mm (1.96 in)	Tracking on the back
Cleaning brush	94 mm (3.70 in)	Tracking on the back; faint calibration patches on the back point to the brush

Other cases from Apple's list:

• Blank pages emptying the paper tray: restart and look at the calibration patches printed on the transfer drum. If they are bands of toner across the drum, replace the laser/scanner unit.
• Jams and blank pages can come from high voltage not reaching the attraction roller, separation discharge assembly or transfer drum; Apple calls this the first Apple printer in which high voltage plays a part in both paper handling and image quality.
• Oil spots, usually on the back of the page, increase if the orange spacers were left inside the fuser access door, if the printer is switched on and off repeatedly (for example five times in an hour), after long standby, or when long use of recycled paper has blocked the oil pan filter.
• Small amounts of toner on the page: clean the density sensor, the separation discharge wire and the pickup area, then print ten blank pages.
• The front door opening too easily causes delays, because the printer runs the cleaning brush after every door opening; Apple's front door latch adjustment tightens it.

ROM 2.0 fixes

Version 2.0 ROM, standard on the 12/660 PS and available for the 12/600 PS as kit 076-0621, fixes system and network faults including NetWare queue polling stopping after 24 hours, NetWare port numbers not being saved, and parallel-port jobs with images failing to print after the protocol was changed from TBCP. Apple's advice is to fit it only when a printer shows one of the listed problems.

Related pages

• Apple Color LaserWriter 12/600 PS and Apple Color LaserWriter 12/660 PS
• Apple Color LaserWriter 12/600 PS General Maintenance
• Color LaserWriter 12/600 PS and 12/660 PS Service Source