Star Tech Journal

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STAR*-rECHJOURNIU~11----------------------M_A_
v _19_a_4_
ON-BOARD
DIAGNOSTICS
DISPLAY TEST
The on-board diagnostics are a
series of tests performed on the
system's hardware to verify whether
or not the hardware is fully func-
tional. Resident in the ZB0A game
program EPROM, the diagnostic
software routines are initiated by
apppropriate option switch setting
when the game is powered up.
Once initiated, the diagnostic
program cycles through the follow-
ing tests. The results of these tests
flash consecutively on the monitor
display.
RAM TEST
Each RAM cell is loaded with 55H
and read to insure that all of the
cells retained the data. The RAM is
then reloaded with 0AAH, which
causes every bit in every cell to be
inverted. The RAM is then read
again to verify data retention. If all
cells are operating properly, the
diagnostics proceed to the EPROM
test. If a bad cell is found, the
system displays "RAM test failed"
on the monitor and halts until it
receives a reset.
The seven-segment Player 1 and
Player 2 displays now cycle through
all of their available digits; each
display should progress through
the numbers 0 through 9. No rating
of PASS or FAIL appears on the
monitor. Simply watch the displays
themselves to ensure that they are
operating properly.
This test checks the operation of
the player controls. During the fif-
teen-second period of the test,
push all of the player control buttons
and operate the joystick. One seven-
segment display corresponds to
each of the controls and to each
direction of the joystick. Each time
a control is operated, a zero should
appear in its corresponding display.
The monitor displays the diagram
shown below, a table indicating
which display corresponds to each
control.
I ACTION I RIGHT I
P2
COLOR TEST
1
2
3
4
5
OFFF6H
OFFFBH
OFFFAH
OFFFCH
OFFFEH
0000H-1 FFFH
2000H-3FFFH
4000H-5FFFH
6000H-7FFFH
8000H-9FFFH
BOUND TEST
1. Connect a composite video
color bar signal at 1.0v pp to the
PCB input at P101 .
2. Adjust sub-contrast (R107)
for maximum contrast with no
overdrive. Overdrive appears as
vertical white bars between the
color bars, most noticeable between
the yellow and cyan bars.
LEFT
I DOWN
UP
I COIN 1 I COIN 2 I
The program now displays the
image of a dead Dirk or a color test
pattern. Adjust the video monitor
till the colors in this image are
satisfactory. This image stays on
the monitor until the diagnostic
dip switch is disabled.
EPROM
Addre88
The program outputs a tone scale
to each of the three channels of the
GI Sound Chip. Check the volume
control while these sounds are
playing. If no sound-is heard, check
the AY-3-8910 Sound Chip.
SET-UP:
PLAYER 2 SCORE
P1
Addre88
Location
May or may not be implemented.
Please disregard.
Set all six PCB controls to mech-
anical center except the sub-
contrast (R107) which is set to the
full clockwise position.
PLAYER 1 SCORE
Checksum No.
SECURITY DEVICE
TEBT
NTSC DECODER
BOARD ALIONMENT
PROCEDURE
PRELIMINARY
KEYBOARD TEST
EPROMTEST
There are five BK-byte EPROMs
within the system. The Diagnostic
program calculates each EPROM's
checksum and compares it to pre-
stored correct checksum values. If
all of the checksums match, the
program continues with the security
device test. If an EPROM fails, the
monitor displays the words "ROM
test failed'' and the address location
of the bad EPROM. The correct
address locations are listed in the
following table:
ELECTRO HOME
MONITOR AND
NTSC DECODER
BOARD
SUPPLEMENT
INFORMATION
SERVICE DIAONOBTICB
AND SIGINATURE
ANALYSIS
A set of ten test EPROMs and docu-
mentation for their use in service
diagnostics and signature analysis
for the 280 controller board are
available at an additional cost. The
troubleshooting procedures using
the test EPROMs assume a rela-
tively advanced level of technical
expertise and are, therefore, not
included in this article.
For information on purchasing
a set of Diagnostic EPROMs, please
contact Cinematronics' Customer
Service Department.
3. Adjust sub-brilliance (R130)
until the black portion of the color
bar pattern just turns black (raster
just extinguished).
4. Critically adjust trimmer
capacitor C124 to center of color
lock-in range. It is a good idea to
power PCB monitor off for a few
seconds, then back on to ensure
color lock.
5. Set chroma input level (R144)
fully clockwise, then rotate slowly
counterclockwise until color dis-
appears, then rotate counterclock-
wise another 30-40 degrees.
6. Connect scope at 1 0
microsec/div (AC couple) to blue
output (P103-6). Adjust L 101 (3.58
MHztrap)forminimum of 3.58 MHz
carrier riding on video signal.
7. With scope at blue output,
adjust sub-brilliance (R130) and
contrast pre-set (R106) for a black
level of 0.5 volts and a peak white
level of 4.0 volts respectively.
8. With scope at blue output,
adjust sub-color (R1 39) so that the
peak level for the grey bar and the
peak level for the blue bar are equal.
9. Connect the scope to the
green output (P103-5) and adjust
the sub-tint so that the peak level
for the cyan bar and the peak level
for the green bar are equal.
10. If necessary, re-adjust the
contrast pre-set (R106) for a peak
white level of 4.0 volts (3.5v above
black level).
NOTE: All of the preceding infor-
mation is taken directly from
Electrohome Electronics'
Service and Operations
Manual G07-19" RGB color
monitor - Jan '81 and
supplement service data:
NTSC Decoder - July '83.