Star Tech Journal

Issue: 1996-January - Vol 17 Issue 11

January 1996
CID
STAR*TEcH
Main PCB Silkscreen
Silkscreening
Shows
Monitor
Monitor Power Supply
Journal
Though a monitor circuit board
looks complex, we are often con-
cerned with only a small part of
it at a time, and it is not too diffi-
cult to follow the printed circuit
traces to make up your own sche-
matic, even if it is just in your
head.
Some manufacturers identify
power supply traces on the PC
board with silk screen hatch
marks or a solder stripe down the
center of an otherwise coated
trace. Learning to trace out your
own schematics will be valuable
in many ways in your bench
work. A little practice makes it
fairly easy.
NUMBER GROUPS
Typical Monitor Power Supply Using Regulator IC
Monitor Power Supply
tOOV AC W'° It•
TSX 1129 -I
I
Many brands give different num-
ber sequences to each section of
the monitor. Part numbers might
group horizontal section parts in
the 600s, power supply in the
900s, and vertical in the 400s for
example. Check the numbers silk
screened on the PC board.
You may find not only these
number groupings, but on some
boards even lines surrounding
the various sections with labels
like VIDEO, SYNC, VERTI-
CAL, etc. Component types and
values can suggest their function.
Electrolytic caps of high voltage
rating (160V, 250V) and a value
of 10 ufd or more are likely filter
caps or maybe a vertical output
cap. Vertical sweep outputs are
usually pairs of transistors on
heatsinks, or on newer units a
multi pin IC for that purpose.
Typical Monitor Power Supply With Discrete Regulator
... continued on page 14
STAR*TEcH
January 1996
Journal
... continued from page 13
FYI
Renewal Time?
Your subscription expiration
date follows your account
number located on the top
line of your mailing label.
Renewal notices are sent 3
issues in advance.
The HOT is readily identified,
and the only other power semi-
conductors in most monitors will
be the regulator in the power sup-
ply and the vertical sweep driver.
~
F.Y.I. STAR*TECH Journal
pays for itself over and over again.
One tech tip many times is worth
a years subscription -or more.
It's as important as any tool in
your shop.
When your coin-op game goes
down, turn to STAR*TECH
Journal to save yourself valuable
time and money.
...
REGIONAL MANAGER
Nat'I Chain-family amuse-
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opports. for dynamic & tech-
nical Professionals. Manage
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multi-stores-midwest, W.
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Must have five years mgt
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F&B ops,. bottom line results,
mechanical (rides & games),
P&L know-how & ability to
manage by the numbers.
Mail or fax your reume to: Hu-
man Resources Director,
Fernandez Entertainment,
91-246 Oihana St., Kapolei,
HI 96707. Fax: 808/682-
4271. EOE.
Points Covered
Look up the part numbers in the
ECG or NTE cross reference
guide. Not only will the ECG
book identify your vertical out-
put IC, but it will provide the
pinout as well. That is the func-
tion of each pin on the device.
1
Intro, troubleshooting phi-
losophy, general approach,
cautions.Three types of
problems described:
Monitor blowing fuses
T'shooting horiz section
T'shooting power supply
Look up your voltage regulator
IC and the book tells you the
output voltage to expect. There
are three color circuits in any
monitor, so when you spot three
similar looking circuits side by
side on the PC board, you have
probably found the video or
color circuits.
Line filter. Isolation prob-
lems. Discussion of ap-
proaches to locating and
identifying components
and circuits.
PC board art
Silk screening
Component types
Literature resources
SIMILAR PRINTS
2
Color/Video problems:
Color gun circuits
CRT
Neck board
Vertical section. General
discussion on capacitors:
High and low voltage circuit
types. Horizontal section.
Horizontal deflection -it
ain't the yoke. Pincushion.
REFERENCES
r
Monitor Repair
Without
Schematics
Other schematics can be helpful.
If you can find another monitor
using the same oscillator IC, use
that schematic for clues as to what
voltages and waveforms to ex-
pect on the mystery unit. That
will work for circuits close to the
IC anyway. Even an unrelated
schematic an be helpful to sug-
gest component functions to look
for.
Part Two to appear in next issue.
See chart on right for topics.
£:1 tY :ti, fi:l
Journal
PART
PART
"Dead" monitor or blank
screen: No power. Bad
power or poor regulation
and associated techniques.
Shutdown: Oscillator tech-
niques. Heat related prob-
lems.

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