January 1996
IVIC>NITC>R REPAIR
WITHOUT SCHEMATICS (PART
1)
Douglas "Enzo" McCallum
Shiawassee Technical Services
Lansing, Michigan
The essence of troubleshooting is isolation of the problem.
Identify the symptom, what does and does not work. A monitor is a system.
Power goes in, signals go in, pictures come out. It is a process.
Troubleshooting is a linear process as well, in parallel with the system.
If we follow the flow of the system it will lead us to the fault.
OBSERVATION
First we must isolate the area of
the circuit that has failed, then we
find out why. Is it system wide?
Is the unit dead? Does it try to
start but can't? Or is the problem
with the sweep? Vertical or hori-
zontal? Complete loss of sweep
or partial? Distorted? Video
problem? Contrast, brightness,
individual color problem? Miss-
ing color? One color stuck on
full? Answering these questions
leads us towards the repair. If we
have a missing color, we need not
look for a failure in the sweep
circuits since sweep affects all
colors equally. Is the problem
constant or intermittent? Does
the symptom occur right away,
or does the unit have to warm up
first.
under test and suitable video sig-
nal for testing. This could be from
your bench setup, or simply from
the game the monitor came from.
OBSERVE SAFETY PROCEDURES
Please be careful working on any
monitor. This article assumes
basic electronic troubleshooting
competence in the reader as well
as at least some monitor experi-
ence. There are dangerous volt-
"The essence of
troubleshooting is
isolation of the
problem.
H
PRETEST NOTE
I leave it to the reader to provide
proper isolated power to the unit
ages in any monitor, both high
DC voltage and the AC line.
Please use an isolation
transformer: Always. You already
expect high voltages to be
present in operating monitors,
but a monitor with a blown sec-
ondary fuse in the main DC sup-
ply can leave behind a fully
charged main filter capacitor, and
it can hold that charge for a long
time. Don't let it catch you by
surprise. Always check with a
meter first. Remember to remove
your rings and wristwatches be-
fore working on a live monitor.
GATHER FACTS
Any good repair starts with a vi-
sual inspection. Look for obvious
broken parts or wires. Are there
any burnt components? If the
flyback transformer is cracked in
half, we know it needs to be re
placed or the monitor retired. Is
the unit mechanically sensitive?
Give the chassis a whack with