Star Tech Journal

NEW YORK (Cont.)
Pyramid Electronics, Inc.
353 E. 76th Street
New York, NY 10021
(212) 628-6500
HilllV
277 Winton Road/Box 100
Rochester, NY 14610
(716) 482-5521
Buckeye Appliance-lV Center
368 E. Whittier
Columbus, OH 43206
(614) 444-1166
NORTH CAROLINA
Gibb's Radio Co.
18 Biltmore Ave.
Asheville, NC 28801
(704) 253-2421
Queen City 1V Service Co.
516 N. Tryon St.
Charlotte, NC 28202
(704) 377-5961
Jim Spencer's 1V Service
5005 Sandlewood Or.
Raleigh, NC 27609
(919) 834-7834
OREGON
Lew Storms Video & 1V Service
4760 S.E. Division
Portland, OR 97206
(503) 233-5971
NORTH DAKOTA
Corwin Churchill Appliance
122 Main/Box 1078
Bismarck, ND 58501
(701) 223-1170
OHIO
1V Electronic Services, Inc.
2076 Harrison Ave.
Cincinnati, OH 45214
(513) 481-6400
Associated 1V & Radio Co.
14807 Madison Ave.
Cleveland, OH 44107
(216) 221-2024
OKLAHOMA
Reynold's Electronic Service
10521 N. May Ave.
Oklahoma City, OK 73120
(405) 751-5604
SOUTH DAKOTA
Karl's 1V & Appliance
19 New York St.
Rapid City, SD 57701
(605) 343-3610
VERMONT
Television Vermont, Inc.
89 Canal St.
Brattleboro, VT 05301
(802) 254-2068
TENNESSEE
Specialized Video & Elect.
180A S. Cooper
Memphis, TN 38104
(901) 276-3515
Able Video Electronics
903 8th Ave., South
Nashville, TN 37203
(615) 256-2852
VIRGINIA
Circuit City Service
2040 Thalbro St.
Richmond, VA 23230
(804) 257-4307
TEXAS
Joseph Sartor Jr., 1V
4512 McKinney/Box 808
Dallas, TX 75205
(214) 526-2114
Bueno Video
6701 Alameda
El Paso, TX 79905
(915) 772-6624
Astro Audio Visual Corp.
1336 W. Clay
Houston, TX 77019
(713) 528-7119
Hopp's Central Service North
2600 West Avenue
San Antonio, TX 78201
(512) 736-4527
PENNSYLVANIA
Blue Mountain Electronics
1112 Linglestown Rd.
Harrisburg, PA 17110
(717) 236-3675
Tesco Inc.
9237 Roosevelt Blvd.
Philadelphia, PA 19114
(215) 677-5000
Serv-U-Service Corp.
5432 Butler St.
Pittsburgh, PA 15201
(412) 782-4411
RHODE ISLAND
Rudden & Martin, Inc.
1884 Westminster St.
Providence, RI 02909
(401) 421-0595
UTAH
Village Television
1661 W. 4800 South
Salt Lake City, UT 84107
(801) 262-3346
SOUTH CAROLINA
Torrence 1V
5122 Two Notch Rd.
Columbia, SC 29204
(803) 786-0388
WASHINGTON
Teletron Service
4415 Aurora Ave.
Seattle, WA 98103
(206) 633-0789
1866-RCAS
616 E. Third Ave.
Spokane, WA 99202
(509) 838-5270
WEST VIRGINIA
1807-RCAS
608 Rock Lane Dr./Box 9276
South Charleston, WV 25309
(304) 768-0051
WISCONSIN
Sunshine 1V & Stereo Service
2044 University Ave.
Green Bay, WI 54302
(414) 432-4537
Star 1V & Appliance Co., Inc.
514 W. Lincoln Ave.
Milwaukee, WI 53207
(414) 672-1242
WYOMING
Stan's 1V & Radio
1615 E. 2nd Street
Casper, WY 82601
(307) 266-1365
MVLSTAR
M.A.C.H. 3 TRDUBLEBHDDTING [CONT.)
INTRODUCTION
...,,e newly developed video-
discsystemingamesrequired
manufacturers to develop new
technologies to utilize these
systems. Mylstar Electronics, Inc.
created a fully interactive game
system using the video disc player
for the background images, and
overlaid
computer-generated
graphics on top. This game system
was created by Mylstar's Engineer-
ing Department by modifying their
GG-111 game computer board, and
incorporating two new PC boards.
I
This technical article will focus on
one of the new boards, the A2
Interface Board. The purpose and
function of this board will be out·
lined, to give a background
understanding of why and how it
works. The second part will con-
centrate on troubleshooting the
board through circuit descriptions
and signal tracing.
The Interface Board's function is to
create a medium in which the two
systems can communicate. The
game graphics computer uses the
data bus and 5 strobes to com·
municate with the Interface Board.
The information going to and from
the video disc player is in four
different signal formats. The Inter-
face Board will operate on three of
those signal formats; the 11-bit
coded Command Control signals
going into the video disc player, the
24-bit Phillips Frame Number code
from the composite video signal,
and the digitally encoded Audio
Track 2/R from the video disc.
Located on the A 1 CPU Board, one
of the Input Ports is a 20-pin DIP
socket which carries the Data Bus
to the Interface Board. This socket
carries three Input Port Select
Functions, IP5, IP6, and IP7, and
three Output Port Select Functions,
OP1, OP6, and OP7. These read
and write control lines will be used
by the CPU to latch data to and
from the Interface Board. This data
is used when the CPU needs to
send commands to the video disc
player, or receive information from
it.
FRAME NUMBER
DECODER
In order to properly start a game
and place the jet fighter and targets
on the screen, the CPU must know
what frame is being displayed on
the screen. Encoded on every frame
in a CAV (standard play) disc is a
frame number, from 1 to 54000,
which is inserted into the vertical
blanking period of every odd field
of each frame. This frame number
is stripped from the composite video
signal on the Color/Sync Board
and is received at the Interface
Board via J3.
The 24-bit bi-phased Frame Signal
is inverted by one gate of A2 (a
Schmitttriggerinverter). Thesignal
is sent to C29, R30, and another
gate of A2 for positive edge detec-
tion, which is inverted once for
negative voltage spikes, and also is
sent to another positive edge
detector (C30, R31, and a third
gate of A2), which is inverted twice
for positive voltage spikes. The
positive and negative voltage spikes
are summed by A4 (a two-input
NANO gate) so that 84 (a non-
retriggerable monostable multivi·
brator) can produce a clock pulse
(FCLK) for the serial to parallel shift
registers. The positive and negative
voltage spikes are inverted by A3
and summed with the clock pulse
to produce Set and Reset pulses
for the D-type Flip Flop (83). This
will produce a serial data train
representing the Frame Number.