Apple Imagewriter Ii.L Service Manual
K
Service Source
ImageWriter II/L
Basics Introduction - 1
Introduction
The electrical operation of
the printer consists of five
printed circuit boards,
three motors, and several
switches.
The boards are the power
supply board, main board,
sub PCB board, print head
board, and the operation
panel board.
Basics Introduction - 2
The three motors are the
carrier motor, line feed
motor, and the ribbon
position motor.
Switches are the home
position switch, paper-out
sensor switch, and the
ribbon switch.
Basics Power Supply - 3
Power Supply
The ImageWriter II/L has a
switching type power supply
that eliminates the need for
a bulky transformer. When
the input AC current is
applied to this board, the
power supply reduces and
rectifies the voltage to the
following DC voltages:
• + 5 V DC
• – 5 V DC
• + 26 V DC
Basics Power Supply - 4
The + 5 and –5 V DC voltages
are for logic; the + 26 V DC
is for motor drive. All the
voltages are fed from
connector CN5 on the power
supply board to connector
CN3 on the main board.
From the main board the
voltages are distributed to
the other boards and motors.
Basics Power Supply - 5
The power supply has two
fuses to help protect the
electronics—FU1 is a 120 V
2-amp fuse and FU2 is a
125 V 4–amp fuse.
Note:
Although not on the
power supply board, there
is another fuse, FU1, located
on the main board that
protects the + 26 motor
voltage.
Basics Power Supply - 6
The on/off power switch is
connected to the power
supply board and disconnects
or connects the main AC
current to the board. The
switch is comprised of a
cable type plunger that is
attached to the power
supply board.
Caution:
is not compatible with the
older ImageWriter II. Do
not attempt to switch the
power supplies between
models.
This power supply
Basics Main Board - 7
Main Board
The main board is the heart
of the printer. Besides
handling the distribution of
the voltages, it also handles
all the logic that controls the
printer. It is also the source
of the drive signals for the
print head. All sensor
signals that affect the
operation of the printer are
fed to this board.
ImageWriter II/L Basics - 8
ROM
The ROM (IC10) chip has the start-up
routines and several features such as
character sets and self-test routines built
in.
RAM
The RAM (IC9) is used in the transfer of
data and acts as a buffer. When printing
starts, the data to be printed is transferred
from the host CPU to the RAM on the
printer. From the RAM the data is passed
through the logic and sent to the print head
to print. Turning off the printer clears the
RAM.
Interface Circuits
The interface circuits (IC2 and IC3) on the
main board handle the data transferred
from the host CPU via the sub PCB board.
These circuits also handle the status and
control lines from the printer to the host
CPU.
Print Head Drivers
The print head drivers (IC5 and IC6)
process the print head drive signals from
the CPU and gate array. The signals are sent
to the print head board through CN5.
ImageWriter II/L Basics - 9
CPU and Gate Array
The CPU (IC8) along with the gate array
(IC4), handles the logic and decisionmaking of the printer. They combine to
evaluate the status of the printer and issue
commands concerning when to transfer
data, when to start printing, when to run
the motors, and what actually prints. All
the functions of the printer are controlled
by these two devices. The rest of the
circuits are supporting circuits.
Carrier Motor Drivers
The carrier motor circuit is made up of
transistors Q1, Q2, Q12, Q13 and IC1. The
transistors make up a circuit that is used as
common returns from the motor. The
transistors also supply the higher voltage
and current needed to drive the motor. IC1
is a transistor pack that completes the
drive signals circuit when turned on. Each
of the four signals drives a phase of the
motor. These drive signals go to the carrier
motor on the printer through CN2.
ImageWriter II/L Basics - 10
Line Feed
The drive circuit is made up of transistors
Q8, Q9, Q10, and Q11. Four drive signals
from the gate array are processed in this
circuit. Higher voltage and current are
added to the phase control signals to turn on
the line feed motor. The signals are sent to
the line feed motor and the ribbon motor
through CN1.
Ribbon Motor Drivers
This circuit is made up of transistors Q3,
Q4, Q5, Q6 and Q7. When turned on, the line
feed motor signals from the gate array are
supplied with more current in the drive
circuit and sent out to the motor. The
common return line is on Q7, which is
turned on for each phase signal sent to the
motor. These signals are sent through CN5.
ImageWriter II/L Basics - 11
Reset Circuit
This circuit is used when the printer is
turned on to keep the logic in a reset state
until the voltages are up to correct values.
Once the voltages are at the correct level,
reset is released and the logic is allowed to
start functioning from a known state.
Connector CN6
This connector is a LocalTalk option card
connector. This card allows the printer to
communicate on the LocalTalk network so
that multiple users can use the printer.
Clock Crystals
There are two clock crystals on the main
board. The clock X1 for the gate array IC4
runs at 17.2 MHz. The clock X2 for the CPU
runs at 12 MHz.
DIP Switches
The configuration DIP switches are mounted
on the main board and can be changed to
make the printer perform in different
modes, or control printer protocols. The
switch settings affect both the CPU and the
gate array logic.
Basics Sub PCB Board - 12
Sub PCB Board
The sub PCB board acts as an
interface board. The
interface cable from the host
CPU is plugged into the
connector CNS1 on this
board. The signals from the
host CPU pass through the
sub PCB board on their way
to the main board. If a cutsheet feeder is attached to
the printer, the signals
pass through the sub PCB
board through CNS2, which
controls the actions of the
feeder.
Basics Sub PCB Board - 13
The paper-out sensor wires
go to this board through
CNS3 and are passed along to
the main board.
All the signals coming or
going to the sub PCB board
are sent through CNS4 and
the ribbon cable to the main
board at connector CN4.
Basics Print Head Board - 14
Print Head Board
The print head board
receives the print head
drive signals from the main
board through CNH1. The
signals are then sent out on
connector CNH2 to the print
head. This board also handles
the ribbon motor drive
signals and the ribbon
switch signals. If the switch
is activated, a color ribbon
is detected.
Basics Print Head Board - 15
This information is sent to
the main board, which in
turn sends controlling
signals to the ribbon motor
to control the position of the
ribbon to allow color
printing.
The home position switch
alerts the CPU that the
carriage is at the far left
side of the printer, which is
home position.
Basics Operation Panel Board - 16
Operation Panel Board
The operation panel board
has the switches (select,
print quality, line feed, and
form feed) and indicators
(error, power, print
quality, and select) mounted
on it. It interfaces with the
CPU through CN7 on the
main board. While the power
switch button is located on
the operation panel, it is not
connected to the operation
panel board.
Operation Panel
Basics Operation Panel Board - 17
The switch button just
passes through to the switch
mounted on the main frame
underneath the operation
panel.
Operation Panel
Basics Operation Panel - 18
Operation Panel
The operation panel consists
Indicator
Lights
Operating
Switches
of operating switches and
indicator lights.
The operating switches are
the buttons with which you
control the printer, and the
indicator lights let you know
what state the printer is in.
Basics Operation Panel - 19
Operating Switches
Power Switch
Power Switch
switch turns the printer on
and off.
- The power
Basics Operation Panel - 20
Select
Switch
Select Switch
- The select
switch toggles the printer
between a selected (online)
and a deselected (off-line)
state. If printing is in
progress when the select
switch is pressed, the
printer finishes printing
the current line and a
maximum of two additional
lines, and stops printing.
Basics Operation Panel - 21
If you want to clear the
buffer, you must turn off
the printer. Pressing the
select switch also clears a
Select
Switch
corrected error condition.
If an out-of-paper
condition exists, pressing
the select switch
temporarily overrides the
error to allow the print of
one line. This process is
repeatable as long as there
is printable data in the
printer buffer.
Basics Operation Panel - 22
Print
Quality
Print Quality Switch
- The
print quality switch allows
the user to choose one of
three printing modes.
Pressing the print quality
switch repeatedly changes
the mode from the standard
print mode, to the NLQ print
mode, to the draft print
mode, back to the standard
print mode again. The print
quality switch does not
function unless the printer
is in an off-line
(deselected) state.Ê
Basics Operation Panel - 23
Form
Feed
Form Feed
- The form feed
switch does not function
unless the printer is in an
off-line (deselected) state.
When the form feed switch
is pressed, the printer
feeds paper until the next
top of form is reached.
Basics Operation Panel - 24
If the switch is pressed and
no paper is present, the
printer assumes a single
sheet is being loaded. The
printer feeds the single
Form
Feed
sheet up to the top of form
position. If the switch is
pressed and paper is
present, the printer
monitors the paper-off
switch while feeding paper.
If the printer detects an
out-of-paper condition
before the top of form is
reached, the printer
assumes that single sheets
are being fed.
Basics Operation Panel - 25
For the single sheet case,
four inches of paper motion
is added to the form feed to
ensure that the page is
properly ejected.
Form
Feed
Basics Operation Panel - 26
When an automatic cutsheet feeder is present, the
paper-loading sequence is
slightly different. When the
form feed is pressed with no
Form
Feed
paper present, the printer
first rolls the platen to
check if a single sheet had
been inserted. If no paper is
found, the printer loads a
sheet from the automatic
sheet feeder and positions it
at the top-of-form position.
Basics Operation Panel - 27
Indicators
Select
Power
Power
light indicates that power is
on.
Select
indicator is lit, the printer
is online, in a ready state so
that a transmission can take
place.
- When lit, the power
- When the select
Basics Operation Panel - 28
Print
Quality
Print Quality
- The print
quality light indicates three
modes of operation:
• NLQ–When both the
left and right
indicators are lit, the
printer is in the Near
Letter Quality print
mode.
• Draft–When just the
left indicator is lit,
the printer is in the
Draft print mode.
Basics Operation Panel - 29
• Standard–If the right
indicator is lit, the
printer is in the
Standard print mode.
Print
Quality
This is the default
mode when the
printer is turned on.
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