Page 6-2
SYMPTOM
Only top
or
bottom
of
vertical deflection present.
Horizontal
scans
right
to
left
instead
of left
to
right.
Vertical scans
bottom
to
top
instead
of
top to bottom.
No
horizontal
or
vertical
sync.
No
characters
on
screen.
(High
and
low
voltage
OK)
ADJUSTMENTS
Video adjustments are located behind
the
front
panel access door
and
on
the rear panel. The B +
Voltage adjustment is located
on
the
main
board.
Refer to Figures 6-1, 6-2, and 6-3.
To adjust the Video controls, use the Display/Key-
board Test, or the ZBASIC Program to fill the screen.
DISPLAY/KEYBOARD
TEST
If
your Z-100 Computer has the diagnostic
ROM
(HE
444-87-5)
at location U190, you may use the Display/
Keyboard Test to fill the screen.
• When the
prompt
appears, type
T.
• Select the Keyboard Test.
• Type any character
and
it
will fill the screen.
.•
Press the
DELETE
key to exit.
AREA
TO
CHECK
•
0601, 0602, 0603, 0604, 0606.
•
Yoke,
TX202A,
open.
•
Yellow
and
black wires
on
yoke
interchanged.
•
Red
and
blue
wires
on
yoke interchanged.
•
0801,0802.
•
C8010pen
•
0806,0805.
•
Wiring
between
boards.
ZBASIC
PROGRAM
•
•
Boot
up
ZBASIC.
Enter
the
following program:
KEY
ON
10
FOR
Z=
1
TO
2000
20
PRINT
"Z";
30
NEXT
Z
40
GOTO
40
•
TYPE
RUN
and
press the RETURN key. The
screen will be filled
with
Z's.
BLACK
LEVEL
CONTROL
The Black Level control is located behind
the
front
access panel. Refer to Figure 6-1. Adjust this control
counterclockwise until the raster is visible.
Then
back
it
down
until the raster just disappears. This
adjustment works best
in
a darkened room.
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