Star Tech Journal

Issue: 1981-May - Vol 3 Issue 3

S*T J
MAY 1981
Signature Analysis is a technique based on data compression to provide a
unique fingerprint of each interconnection or test node in the unit under test (UUT).
The Signature Analyzer provides the technician with a test probe that can be used to
enter data to be recorded and read out for the test node.
I
I
1
2
4
3
WORDS
Signature Analyzers convert serial bit streams into a 4 hexdigit "Signature".
Since a unique signature is generated for each data stream a prime requirement is
that the data stream passing a node be identical (unless faulty) for the same node on
each identical board. The second requirement is that this data stream repeat itself.
This repetition is assured by having a start and stop pulse which is time and polarity
related to the data stream.
1
2
3
4
5
6
7
8
9
l 10
CLOCK
START/STOP
DATA
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START
STOP
FIGURE 1
If we start the Signature Analyzer by placing "Start" on the rising edge ( _r- )of
the first pulse on line 2 above and the "Stop" on the rising edge ( _r- ) of the 2nd
pulse labeled "Stop" we will allow clock pulses 2 thru 9 to enter the system. There is
one data bit entered into the compression circuit for each clock pulse.
In figure 1, the data stream entered would be: 01011011
This stream would be entered each time the window is generated.
To demonstrate how a single bit difference between two data streams affect the
"Signature" consider these two streams:
ll l ll 111100000111111 = D953
11111111100000011111 = 99F6
Either a bit difference or a displacement by time ( clock pulses) gives a totally
different signature - not one digit or segment difference.
Certain portions of a processor system not designed for Signature Analysis can
cause some problems but by and large following a few simple rules will overcome
these problems.
Next month we will take a processor system from the beginning and follow through to develop
signatures.
7
S*T J
MAY 1981
8
ATARI ''MISSILE COMMAND''
diagnostic tests
INSTRUCTION
1 . Set self-test switch to on
position. Note: entering self-
test will set the HIGH SCORE
TODAY display to 7500.
USE OF TEST
2. Press alpha base fire
button and slam switch simul-
taneously. Release slam
switch first.
A convergence pattern appears on the monitor screen. The background can be
many possible colors. If you are going to converge the monitor, black is the color
you want. To change background color, press either START button. Do not
attempt any convergence adjustments unless you are a qualified color TV
technician!
3. Press omega base fire
button and slam switch simul-
taneously. Release slam
switch first.
Vertical color bars appear on the screen, to permit color hue and brightness
adjustments. Pressing either start button changes the color of the right and left
vertical bars. Do not attempt any color hue or brightness adjustments unless
you are a qualified color TV technician!
4. Press delta base fire
button and slam switch
simultaneously.
White screen appears, and tiny black dots trace all the raster lines from top to
bottom (takes about 4 7 seconds). After this, a blue RAM OK message appears on
the screen, and the+ will reappear. If the message BAD RAM appears and some
or all of the digits 1 thru 8, refer to the following to determine the failing RAM chips.
Test no. 4 display
Bad chip location
BAD RAM 8
P4
BAD RAM 7
N4
BAD RAM 6
M4
BAD RAM 5
L4
BAD RAM 4
K4
BAD RAM 3
J4
BAD RAM 2
H4
BAD RAM 1
F4
Check attract mode display and readjust brightness if necessary.
5. Set self-test switch to
off position.
ROWE BILL CHANGER M o d i f i c a t i o n s
There have been field reports of some BC-20, BC-25, BC-11 and BC-115 Bill Changers spontaneously attempting
to pay out - without input of a bill or coin. This usually results in an immediate shutdown, but in some cases one
change load has been paid out before shutdown.
Upon checking, the Diagnostic Status Code Indicator will display "F", with Fault LED flashing.
The cause of these spontaneous pay-out attempts has been traced to inadvertent "turn-on" of one of the three
bucket solenoid drive transistors - either Q 15, Q 16 or Q 17 - on the Computer Control Center. (This can be a
result of either electrical noise or thermal stress.)
The situation can be corrected in either of two ways:
1.
Replace the defective Computer Control Center with a new or re-worked one from the factory, returning the
defective one for credit. Note: All updated Computer Controls will have a light red dot affixed to the reset
button, and an inspection label dated December 1980 or later.
2.
Re-work the defective Computer Control Center by replacing the three (3) bucket solenoid drive transistors
and the six (6) associated resistors as follows:
Q 15, Q 16 & Q 17 Transistors
REPLACEMENT
Darlington Transistors
Rowe p/n 7-00308-08
(TIP-102 or Tl P-132)
R-54, R-57 & R-58 Resistors
Rowe p/n 7-09901-331
(330 Ohms, 1 /4 W)
R-55, R-56 & R-59 Resistors
Rowe p/n 7-00107-24
(22 Ohms, 1 /2 W)
The replacements mentioned can be ordered from Rowe, Grand Rapids (no charge).
For further Technical information, contact Rowe Field Services at this toll-free number, 800-631-8084.

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