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Apple LaserWriter Plus

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Revision as of 19:43, 23 September 2026 by Josh (talk | contribs) (See Also: add Personal LaserWriter 300 for consistency with the rest of the LaserWriter cluster)
Apple LaserWriter Plus
Apple LaserWriter Plus
Manufacturer Apple Computer, Inc.
Type Laser printer
Interface AppleTalk (DB-9), RS-232 (DB-25)
Compatible Macintosh; MS-DOS computers via RS-232
Dimensions 11.5 in. H x 18.5 in. W x 16.2 in. D (28.2 in. with trays)
Weight 77 lb
Power 100-115 V AC 60 Hz (domestic); 220-240 V AC 50 Hz (international)

The Apple LaserWriter Plus is the Apple LaserWriter with a larger ROM. Apple's service documentation treats the two as one product throughout: a single tab section, a single parts list, a single set of troubleshooting tables, and one specification line that differs — "512K ROM (LaserWriter) and 1 MB ROM (LaserWriter Plus)".[1]

Everything mechanical, electrical and procedural is therefore on the Apple LaserWriter page and is not repeated here: the specifications, the safety rules, the four status lights, the test prints, the pre-power-on checklist, the laser power and image skew adjustments, the preventive maintenance schedule and the parts list. This page covers only what is specific to the Plus.

What Is Different

LaserWriter against LaserWriter Plus[1]
LaserWriter LaserWriter Plus
Marking engine Canon LBP-CX Canon LBP-CX
Processor 12 MHz 68000 12 MHz 68000
RAM 1.5 MB 1.5 MB
ROM 512K 1 MB
Resolution 300 dpi 300 dpi
Speed 8 ppm 8 ppm
I/O board part number 661-0436 661-0437

The larger ROM is what holds the larger font set. Apple's Volume I guide does not state a font count for either model, so no such figure is given here; the guide does list Times, Courier, Symbol, Palatino, Helvetica, Helvetica Narrow, ITC Bookman, ITC Avant Garde, ITC Zapf Chancery, New Century Schoolbook and ITC Zapf Dingbats as the built-in font families of the LaserWriter II NT, which carries the same 1 MB ROM.[1]

ROM Layout

The two boards are distinguishable by their ROM complement in the parts list:[1]

  • LaserWriter I/O PCB (661-0436) — eight ROMs, in high/low pairs H0/L0 through H3/L3, part numbers 342-0081 to 342-0088.
  • LaserWriter Plus I/O PCB (661-0437) — sixteen ROMs, H0/L0 through H7/L7, part numbers 342-0089 to 342-0104.

Both boards also take a LaserWriter Configuration Block, part number 750-0102, and a 16-pin IC socket, 511-1603.[1]

The ROM Upgrade

Apple published a field upgrade from LaserWriter to LaserWriter Plus. This is the one procedure that belongs only on this page, and it is worth following exactly because there are three board variants with different configuration arrangements.[1]

  1. Switch off, put the printer on a grounded workbench pad, and put on your grounding wriststrap.
  2. Remove the top cover and the LaserWriter I/O board; place the board on the grounded pad.
  3. Using an IC extractor, remove all ROMs from rows E and F on the I/O board. There may be four, eight or sixteen ROMs installed — remove them all.
  4. If the board has no 16-pin socket at location E-20, fit one: desolder and discard the four jumper wires at the socket location, desolder all sixteen holes, then fit the socket on the component side so its sixteen pins match the holes, and solder all pins.
  5. If the board is a 256K/512K I/O board, install the configuration block at the socket labelled "512K".
  6. If the board is a 512K/1M I/O board, install the configuration block at the socket labelled "1M".
  7. If the board has the 512K/1M jumper, install the jumper at the set of pins marked "512K".
  8. Install the upgrade ROMs, matching the marking on each chip to its socket location. The notch along the edge should face the three rows of RAM on the board.
  9. Replace the I/O board and switch on. The printer should produce a user test print within two to three minutes.
  10. Find the PostScript ROM revision number on the user test print. The upgrade is successful if it shows Rev 3.0.
  11. If no user test print appears, verify the ROMs are properly installed; if they are, fit known-good ROMs from a LaserWriter Plus Kit, or run the LaserWriter/LaserWriter Plus built-in diagnostics.

Steps 5 to 7 are the trap: the configuration block or jumper position depends on which board you have, and getting it wrong produces a printer that does not produce a test print at all — exactly the symptom step 11 addresses.

Diagnosing a Plus

The same principle as the base model, with one addition specific to this page:[1]

  • Service test print — jumper J205-1 to J205-2 on the DC controller PCB. Tests the print engine alone.
  • User test print — produced at every power-on unless suppressed. Tests the I/O board, and reports the PostScript ROM revision, the operating mode and the page count.

On a Plus, the user test print is also the way you verify the ROM set. A machine that prints a perfect service test print but no user test print has an I/O board or ROM fault, not an engine fault — and on an upgraded machine, the first thing to check is the configuration block position.[1]

Safety

Identical to the LaserWriter, and it applies in full: an invisible laser behind an optical fibre that can permanently damage your eyes, a fuser that needs five minutes off before you touch it, a high-voltage supply, and ESD-sensitive CMOS on the I/O board — which you will be handling during the ROM upgrade above. Remove jewellery, do not be grounded when working on plugged-in equipment, and handle the ROMs by their edges.[1]

Service Manual

See Also

References

  1. ↑ 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 Apple Service Guide for LaserWriter Printers, Volume I, Apple Computer, Inc., January 1992 (072-0631-B) — hosted on this wiki as File:Apple LaserWriter Printers Volume I.pdf. Covers the LaserWriter, LaserWriter Plus, LaserWriter II SC/NT/NTX/IIf/IIg and Personal LaserWriter SC/NT/LS. Introductory safety section: the high-voltage, optical-fibre, fuser-cooling, ESD, not-being-grounded and lifting warnings; the LaserWriter Safety Rules; the toner-safety paragraph; the laser-safety paragraph and the three laser warning labels. Tab 2, LaserWriter/LaserWriter Plus: parts list with part numbers (pages 3–4); print engine specifications (page 7); status lights (page 8); service test print and user test print (page 9); the pre-power-on checklist and troubleshooting flowcharts and tables (pages 10–51); the LaserWriter Plus ROM upgrade (pages 52–53); the laser power adjustment (page 54); the image skew adjustment (pages 55–56); and preventive maintenance including the page counter, the maintenance schedule and the Standard Maintenance and 100,000-Page Service checkpoint tables (pages 57–60). Tab 3, LaserWriter II: parts list (pages 4–5); controller-I/O board specifications (page 10); print engine specifications (page 11); status LEDs (page 12); test pages (page 13); the pre-power-on checklist, the IIf/IIg status-LED diagnostic chart and the troubleshooting tables (pages 14–54); the laser power output check (page 55); the NTX memory and ROM upgrades (pages 56–57); the IIf/IIg memory upgrade (page 58); and preventive maintenance (pages 59–60). Tab 6, Ports and Cables: the peripheral cable table, external connector diagrams, connector pin-outs and switch configurations.


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