Apple LaserWriter 16/600 PS Troubleshooting Guide

The 16/600 PS DC controller board, from Apple's Service Source: C208 at the left, VR201 at the top, and the connectors used in the voltage checks.

Fault-finding for the Apple LaserWriter 16/600 PS, from Apple's Service Source for the printer. The 16/600 PS shares its case and its troubleshooting framework with the Apple LaserWriter Pro 600 and Pro 630. Apple's 36 troubleshooting tables for the two printers are the same text apart from two changes: the fuser capacitor is C208 on the 16/600 PS (C202 on the Pro), and the fan table covers three fans. The shared tables, with their voltage readings, the safety notes for live work, the probe test, interlock defeats and drum check, are given once on Apple LaserWriter Pro 600/630 Troubleshooting Guide. The sections below cover what differs.

Before working inside, read the safety notes: switch off and unplug, never disconnect the beam-detect cabling or laser shutter with power on, never remove the laser/scanner cover, and leave the printer off for at least 5 minutes before touching the fuser rollers.

Start-up lights and POST

A healthy 16/600 PS lights all four LEDs for a moment about a second after switch-on, then the lights pulse as the fans and main motor start. About 5-6 seconds in, all four light again for a second: this is the start of the power-on self test (POST), run by the I/O controller board. POST checks four areas in turn: the SIMMs and CPU, the I/O controller, the engine, and the fax card or hard disk if fitted. The leftmost LED goes out as each check passes. When all four have passed, all the LEDs stay off for a second, the Ready LED flashes once, and control passes to PostScript.

During POST the lights do not mean jam, low toner or paper out. If POST finds an error it stops the sequence and flashes the toner and jam LEDs alternately until the printer is switched off. Note which lights had gone out before the error: that points to the area that failed.

Extended POST (EPOST)

EPOST is the technician's version of POST and reports a more specific code.

1. Switch off. Fit a serial loopback connector to the I/O controller's serial port and set the configuration switch up.
2. Switch on. EPOST runs like POST until it finds an error.
3. On an error the lights repeat a cycle: all on for 1 second, all off for 1 second, the error code for 2 seconds, all off for 1 second. A pattern not in the table below is an unknown error.
4. Afterwards remove the loopback connector and return the configuration switch to its original position.

Apple's loopback connector is a male mini DIN-8, part 922-1489, also supplied in Apple's diagnostic kits. To make one, join pins 1 and 2 of a male mini DIN-8 plug with a short piece of thin wire-wrap wire. Apple's flowchart, for a Ready light that flashes without stopping, and its table 3, for a lit toner LED, both say to check that the loopback connector is out of the serial port.

EPOST error codes (LEDs from left to right)

LED 1	LED 2	LED 3	LED 4	Fault
Off	Off	Off	On	I/O controller board
Off	Off	On	Off	ROM SIMM A
Off	Off	On	On	RAM size
Off	On	Off	Off	RAM SIMM (low)
Off	On	Off	On	RAM SIMM (high)
Off	On	On	Off	Engine controller (interface or NVRAM)
Off	On	On	On	Fuser assembly
On	Off	Off	Off	Laser/scanner assembly
On	Off	Off	On	Miscellaneous engine (operator or unknown error)
On	Off	On	Off	Engine fan (one or more)
On	Off	On	On	Main motor
On	On	Off	Off	SCSI hard disk (present but failing)

A RAM size error can come from an unsupported memory layout. Apple supports only 8, 12, 16, 24 and 32 MB in the combinations listed on the main page and says others are likely to give an engine error at start-up. A hard disk that is not switched on before or with the printer also stops it starting.

Working with the I/O board out

To run the printer from a computer with the engine open, remove the rear panel, the I/O controller board and the I/O shield. Take the printer interface cable off the I/O board and fit a Quadra 900/950 floppy drive 20-pin cable in its place, with its free end on J207 of the DC controller, and reconnect the power cable to J15. The other access methods (pickup block, sheet feeder bypass, envelope feeder without covers) are the same as on the Pro 600/630.

Fuser error and C208

After a fusing failure the DC controller cuts the heater and charges C208. Leave the printer off for about 10 minutes, or:

1. Switch off and unplug.
2. Remove the rear panel, the I/O controller board and the I/O shield.
3. Short the two wires at the base of C208 (left side of the DC controller in the drawing) with a conductor. Apple shows a length of lead solder, which bends easily and is less likely to damage the board.

The fuser checks in table 6 are identical to the Pro 600/630's: thermistor 180-280 kΩ across J743-6 and J743-7 with the fuser out and cool, heater and thermoprotector about 3 Ω or less across J743-1 and J743-8, /FSRD at J212-1 falling from about 5.1 V to 1.5 V after start-up, and RLD at J212-2 about 2.1 V.

Fans

The 16/600 PS has three fans where the Pro 600/630 has one. Table 9 is Apple's:

Table 9, fan error

Check	Expected	If not
Fan cables at J209, J214 and J213 on the DC controller	Secure	Secure them
FM1 (power supply fan, J209) and FM2 (controller board fan, J214) blow out through the case vents. FM3 (internal fan, J213) blows inside and runs only while printing, so the top cover has to be off and the sensors defeated to see it. Measure pin 1 (fan drive) to pin 3 (ground) at each fan's connector at switch-on	Each rises from 0 V to 24 V, then drops to about 16 V	Replace in turn the DC controller, the power supply and the faulty fan
J209-2 (FLOCK) to J209-3 at switch-on	2.2 V or more	2.2 V or more: replace the power supply fan (FM1). Less: replace the DC controller

The other tables

Apple's tables 1-5, 7, 8 and 10-36 for the 16/600 PS (power, status lights, paper-out, jams, laser/scanner, main motor, I/O board, print quality and paper transport) carry the same steps, connectors and readings as the Pro 600/630's, which are tabled on Apple LaserWriter Pro 600/630 Troubleshooting Guide. Table 24 there, on PhotoGrade, matches the 16/600 PS: Apple's RAM table gives 12 MB as the minimum for PhotoGrade on this printer.

Network faults

Several network symptoms are fixed by version 3.0 of the I/O processor (IOP) ROM, part 922-2458. The version is printed along the right edge of the startup page as "I/O: xx". Apple lists:

• Ethernet lock-up after the printer receives a packet over 1518 bytes (version 1.0); restarting clears it for a time.
• EtherTalk stops responding during or after a broadcast storm while TCP/IP and IPX keep working.
• The printer registers with a numbered name, or appears in the wrong zone.
• The printer shows in the Chooser but will not print. Apple says to try LaserWriter 8.2.2 or later and to check for the router NBP gleaning bug in Cisco software before v10.2 and in Apple Internet Router 3.0 before changing the ROM.
• The printer is invisible on networks with Dayna PathFinder routers.
• Slow printing, or occasional PostScript errors, through a Farallon PhoneNET StarController.
• A job that fails with no end-of-file marker takes the next job with it; the third prints.

The printer returning to its default zone after a restart is not a ROM fault: the configuration switch must be up for zone changes made with the Apple Printer Utility to persist.

Registration

The procedure is the same as on the Pro 600/630, but the control is VR201 on the 16/600 PS DC controller. Apple requires it after replacing the DC controller, the paper pickup block or the laser/scanner. Set VR201 to 0, print three service test pages, average the distance from the top edge of the page to the pattern, and turn VR201 clockwise if the average is under 2.0 mm or anticlockwise if over; each step is about 0.3 mm. The worked example on Apple's page has the same sign error as the Pro manual's: a 2.6 mm average needs −2, not +2.

Related pages

• Apple LaserWriter 16/600 PS General Maintenance
• Apple LaserWriter Pro 600/630 Troubleshooting Guide
• Apple LaserWriter 16/600 PS
• LaserWriter 16/600 PS Service Source