Star Tech Journal

Issue: 1983-January - Vol 4 Issue 11

15
STAR*TECH JOURNAL/JANUARY 1983
SEGA
ELECTRONICS
SYMPTOMS AND SOLUTIONS
"TURBO" VIDEO DISPLAY
"MONACO GP" 1 COIN/1 PLAY MOD
"SPACE FURY'' MOVING LINES
* * *
"Turbo" Video Display
Symptom: Moving white columns appear where the cars are supposed to
be, and the self test fails to indicate a reason.
Solution: On page 143 of the "Turbo" Owner's Manual (PIN 420-
0681), Zone4B-D of Drawing No. 834-0111, Sheet 1 ofl0, you will notice
a number of filter/line drop capacitors of 100 pf value (i.e. C21, C28). One
of these caps is bad and usually a visual inspection will reveal one that has
physically split. (They're small, so look closely!) If they look alright, pull
one side, check it in the conventional way, and the bad one will tum up.
*
"Monaco GP" 1 Coin/1 Play Mod
Symptom: How to set "Monaco GP" for 25¢ play. (The coin selection
board only has settings for 50¢ or 75¢ play.)
Solution: There are actually two methods of setting your game for 1
coin/1 credit. The first involves acquiring a 1-2-3-4 Coin Select Option
Board (S-96786-P) and exchanging the new for the old.
A more expedient way is to remove your 2-3 Coin Board entirely
(located in the door), connecting inputs to outputs as follows:
Red input to red output. Blue input to blue output. Leave all white wires
connected together, and DO NOT connect the yellow wires (insulate wire
ends and leave them open).
*
"Space Fury" Moving Lines
Symptom: Every once in a while "Space Fury" gets faded, moving lines
on the right side of the screen.
Solution: In order to eliminate occasional extraneous vectors from the
right edge of the color X-Y monitor display, please make the following
corrections to your Owners Manual (PIN 420-0605) and the X-Y Timing
Board:
1. Add to the Parts List:
Item No. Part No. Qty. Req'd. Description Ref. Des.
2
CAP CER
C32, C33
40
151-0002
100 pf 50V
2. On page 40, sheet 5, zone D4 and B4 of your Owners Manual, add the
capacitors to the schematic as shown and;
3. install C32 between pin 2 and pin 6 ofU2. Install C33 between pin 2 and
pin 6 of U3.
Courtesy of Sega's "Data Bus"
School For
Electronic
lames
TWO-WEEK COURSE
COVERS VIDEO AND
PINS. BY SCHEMATICS!
OUR 11th YEAR!
Cals
Coin
College
P.O. BOX 810
NICOMA PARK, OK
73066
405/769·534
STAR*TECH JOURNAL/JANUARY 1983
16
tMNUFACTs.
SUMMARY OF MAJOR OP-AMP CIRCUITS (PART 1)
By Frank Becker, Atari, Inc., Somerset, NJ
This 3-part series is written as a quick reference guide on
OP-AMP circuits for technicians and will not get into
detailed mathematical analysis. Such detailed analysis
can be obtained from any good electronics text book.
-------
As the name implies, the inverting OP-AMP configuration
inverts the input and provides gain that is determined by
the values of resistor RF (for feedback resistor) and RI
(for input resistor).
Voltage gain for the Inverting OP-AMP:
OP-AMPS
The term OP-AMP stands for Operational Amplifier. Its
most important characteristics are summarized below:
AV=Vo=-RF
Vin
RI
I. Very high open-loop gain:
The ideal OP-AMP has infinite open-loop gain. This is
voltage gain without any feedback resistors.
(Minus sign means inversion.)
2. Very high input resistance.
AV= -RF= -IOOK = -10
RI
IOK
3. Very low output resistance.
Example 1: If RF= IO0K and RI - I0K, what is the
voltage gain AV?
BASIC OP-AMP SYMBOL
v+
1v
power>
IN
0
-1v
output
Non-inverting _ _ _,
input
+
10v
V- power>
*Power lines are sometimes not drawn for simplicity but
are always there.
OUT 0
-10v
DEFINITION OF TERMS
Inverting input - Output signal and input signal are
inverted. (See Inverting Amplifier.)
Non-inverting input -
phase.
Output and input signals are in
AV - Voltage Gain - Defined as Av= V out
Vin
-AV - Same as above but output signal is inverted from
input ( 180° out of phase).
Example 2: "Gravitar" audio output
R1
V10-
10K
3.9K
-- -N\J'N-
1
V2
INVERTING AMPLIFIER
>-~-AUD2
RF
Al performs two functions: Sums VI and V2 and inverts
the inputs.
RI
Vin
Vout
Voltage gain for signal VI:
For VI, AV= -RFI = -3.9K = -.40
RI
I0K
For V2, Av = -RFI = -3.9K = -I
R3
3.9K

Download Page 15: PDF File | Image

Download Page 16 PDF File | Image

Future scanning projects are planned by the International Arcade Museum Library (IAML).

Pro Tip: You can flip pages on the issue easily by using the left and right arrow keys on your keyboard.