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K Service Source
LaserWriter 8500
K Service Source
Overview
LaserWriter 8500
Overview About This Overview - 1
About This
Overview
This overview briefly
describes the servicing
issues of the LaserWriter
8500, especially those that
distinguish it from earlier
Apple laser printers.
360 Degree View
LaserWriter 8500 Basic Configuration
Overview General - 2
General
The LaserWriter 8500 is a 600 dpi, 20 ppm monochrome
laser printer that is capable of printing onto paper up to 13
x 20 inches in size. In its basic configuration, the printer
has a capacity of 650 sheets, the standard cassette holding
500 sheets (as compared to the 250 typical in earlier
printers), the multipurpose tray holding 150.
There are several options available for the printer,
including a duplexer unit (for two-sided printing), a 500-
LaserWriter 8500 with sheet feeder, and an envelope cassette.
Duplexer and Sheet Feeder
360 Degree View
Overview Duplexer - 3
Duplexer
The duplexer is an inverted L-shaped feeder that mounts
onto the upper rear of the printer. Once installed, all paper
(even simplex) diverts into and exits from the duplexer.
This is unlike the LaserWriter 12/640 PS, which employs
a solenoid-actuated diverter controlled through software.
Duplexer The operative element in the LaserWriter 8500 is the
exchange chute, located in the fuser assembly. The exchange
chute is actuated (i.e. locked in place) during installation of
the duplexer.
After the first pass of a duplex page, the paper partially
exits the duplexer delivery rollers. The rollers then
reverse and the paper feeds back down through the duplexer
and into the printer engine, in preparation for imaging of
Paper Path the second side. The paper then exits through the duplexer
Through Duplexer
into the delivery tray.
Overview Paper Path - 4
The duplexer derives its power from the printer engine but
has its own motor to generate mechanical drive.
Offset Function
The duplexer has a job separation feature that allows print
jobs to be stacked offset (i.e. staggered left-to-right) in the
delivery tray. Job separation is set in the Apple Printer
Utility.
Note: Due to cost considerations, the offset function has been
incorporated into the duplexer instead of the printer engine.
Offsetting and duplex printing are otherwise unrelated to one
another.
The offset motor in the duplexer generates the mechanical
drive for offsetting paper.
Overview Sheet Feeder - 5
Sheet Feeder
As with the LaserWriter 16/600 PS and LaserWriter 12/
640 PS designs, the sheet feeder fits squarely beneath the
printer to form a dual front-loading cassette arrangement.
Unlike those models, however, you can stack two feeders
Sheet Feeder beneath the printer, for a total auxiliary capacity of 1000
sheets. Also unlike those models, the sheet feeder and the
engine use identical cassettes in the LaserWriter 8500.
The sheet feeder derives its power and mechanical drive
from the printer engine.
Overview Form Factor - 6
Form Factor
C
To achieve a reasonably compact form factor, the tail end of
the cassette has been designed to extend out from the engine
footprint (A). Consequently, the pickup rollers feed from
D the insertion end of the cassette (B), similar to the Laser-
A
Writer II. This arrangement influences the architecture of
B
the printer in the following ways.
1 Because pickup occurs deep within the printer, all
Printer Cross-Section mechanical drive elements are arranged vertically along
Note: Diagram shows printer the rear (C), resulting in a simple C-shaped paper path.
with long cassette and over- This vertical arrangement yields a compact, low-
size (11 x 17 inch or A3) maintenance gear train, consisting at its essence of one
paper installed.
gear assembly driven by one central motor.
2 You can stack letter-sized paper on the multipurpose
tray and shut the cover (D), thus hiding that paper from
view inside a multipurpose "compartment."
Overview Form Factor - 7
3 The design of the cassette bottom plate (A) is new.
A
Below the plate, three springs provide upward pressure
C that forces the paper against the pickup rollers. (Only
two of the springs are activated when the width guides
B (B) are set for narrower paper). In most printers, the
bottom plate receives constant uniform pressure from
C
the springs. As you insert the cassette, the paper snugly
and passively presses against the pickup rollers.
With this printer, however, the bottom plate must stay
down during insertion to avoid snagging. The springs are
released, and the bottom plate elevated against the pickup
rollers, only when the cassette is fully inserted.
This spring release is actuated by a latch on each side of
the cassette near the leading edge (C). See "Cassette" in
the Basics chapter for more information.
Overview Paper Orientation - 8
Feed Paper Orientation
The paper path is wide enough to print letter or A4 sized
Long-Edge Feed paper in long-edge feed (LEF) mode. LEF mode is recom-
(LEF)
mended as it achieves the fastest 20 ppm throughput and
optimizes duplex printing.
Feed
Note: The cassette automatically senses paper orientation.
The multipurpose tray does not. Printing in short-edge feed
Short-Edge Feed
(SEF) (SEF) mode from the multipurpose tray may produce
undesirable results.
Paper orientation and how best to load paper can be
confusing, especially when talking with customers over the
phone. It is further complicated when printing duplex jobs.
Keep in mind the following tips: