o THEORY OF OPERATION
Introduction
Troubleshooting can be approached in different ways;
Apple usually recommends both module swapping and
logical troubleshooting. But random module swapping is
impractical for printers because they have so many parts.
So, to troubleshoot the ImageWriter II, you will usually
want to use the logical troubleshooting method. A
description and diagram of the flow of information in the
ImageWriter II are given below as aids to this method.
Before You Begin
Before you begin to troubleshoot the ImageWriter II,
attempt to run the self-test before you connect the printer
to a computer. Then, if the self-test does not run correctly,
you can observe where it stops working. Knowing the
flow of information, you will be able to isolate the problem
to the faulty module.
Flow of Information
Figure 9 is a block diagram of an ImageWriter II printer.
The numbers on the diagram indicate the order in which
the self-test takes place and correspond to the following
descriptions.
1.
The AC power cord is plugged into a wall socket and
into the power inlet on the right support leg.
2.
The power switch on the operation panel is turned on
and the form feed switch is held down. The AC
voltage and current are passed through the filter to
reduce radio frequency interference (RFI) to FCC
standards. The 120 volts are sent to the transformer,
where they are reduced to 40 volts.
3. The 40 volts are sent to the drive PCB. Here the
voltage is broken down and sent to the various parts
that need it. The drive PCB contains the power supply
and all of the motor and print head drive circuitry. The
drive circuitry controls the firing of the hammer and
limits the current to the print head.
1.14
/ Basics
rev. Aug 87 ImageWriter II
