Apple LaserWriter 12/640 PS - Manual (Page 218)

Precautions during maintenance
To prevent damage to the printer while performing maintenance, observe the
following precautions.
m Don’t lubricate the printer.
m Don’t attempt to disassemble the printer.
m Don’t place anything on top of the printer.
Regular maintenance
The toner cartridge holds the toner powder that forms the printed images.
Each cartridge should yield about 6,000 pages. If you print many graphic
images, you may need to change cartridges more often. If your pages start to
look too light, or if you see vertical white regions in dark images, it may be
time to change the cartridge.
For ordering information, see Appendix D.
Replacing the toner cartridge
Whenever you install a new toner cartridge, you should also clean the interior
of the printer. Follow these steps to replace the cartridge and clean the
interior of the printer.
WARNING Use only cartridges designed for use with your LaserWriter
12/640 PS Printer. Other cartridges may not fit and may damage
the printer
219 Maintenance