Star Tech Journal

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STAR*TECH Joumal
March 1992
Merit Pub 'nme Darts
Vertical Height
And Linearity Problems
Sam Cross
Godwin Distributing
N. Little Rock, Arkansas
SYMPTOM
PROBLEM
SOLUTION
On Pub Time Darts by Merit In-
dustries using the Hantarex 9"
amber colored monitor, you may
have insufficient vertical height
and bad vertical linearity on the
monitor.
Thinking this was the monitor at
fault, I substituted a different
video signal and the monitor dis-
played a decent picture. Putting
the monitor back into the game, I
then proceeded to turn the volt-
age up on the power supply. A
decent picture appeared after a
I eventually replaced the
TMS9118 Display Controller,
U25, with a TMS9128 which is
pin for pin compatible. I was then
able to return the 5vdc adjust-
ment back to normal.
Merit has had problems with their
TMS9 7 7 8 chips
and has begun to substitute the
TMS9728 in it's place ...
That is, it has wide-spaced hori-
zontal lines near the top, badly
crunched two thirds of the way
down, then too widely spaced the
rest of the way to the bottom of
the screen.
voltage of 5.35vdc was reached.
Knowing this board didn't have to
be at this voltage to display a good
picture, I figured that something
must be going out (borderline op-
erational) on the board.
SOURCE
Merit has had problems with
their TMS9118 chips and Has
begun to substitute the TMS9128
in it's place. It is available from
the factory, parts supplier
Semitech, or your favorite Texas
Instrument dealer.
Semitech Inc
146 S. Lakeview Drive #303
Gibbsboro, NJ 08026
800/356-3759
Fox 609/784-1993