Star Tech Journal

14
4) CMOS RAM Section - This includes the CMOS (6514) RAM, three double
AA batteries to power it (when the game is turned off), and a few ICs in the power
up/down (write enable) circuit. Failures in this section usually result in bad audit
totals, or the game powering-up in diagnostics (bookkeeping) mode and printing the
message "high score table reset". Please remember that the batteries are not Nicad
rechargeables and are going to have to be replaced periodically. The memory protect
switch ( interlock switch on front door) and input gate ( 6E) on the board itself should
also be checked if any bookkeeping failures develop. Please take note that the
CMOS RAM is checked during the self-test procedure and that there is a "CMOS
RAM Data Test Protocol" explanation and flow chart on the back page of every
instruction manual.
5) Reset Section - (including watchdog). This section includes all the transistors
in the power up reset circuit, the push button reset switch and approximately 4 I Cs
in the watchdog circuit. The watchdog circuitry is designed to detect any variations
from the program. If everything in the CPU and memory section is not functioning
perfectly, this circuit will generate a reset pulse to the processor. There actually is
numerous (protection) circuitry on this board with the watchdog being the principle
element. Failures of this circuit will be self evident(scope pin 37 on the 6809). If the
processor is not reset (told where to start), then it won't start at all.
6) Sync and Video Out - The sync and video out section includes the 3 output
color driver transistors (QI, Q2, and Q3) and the 3 sync signals for the monitor
(composite, horizontal, and vertical). Failures in this circuitry should also be
apparent ( rolling picture, no picture, missing or wrong colors). This color circuitry
is capable of creating 256 different colors (shades) and is usually very reliable.
ROM/PIA BOARD - The ROM board is interfaced via a 40-pin ribbon cable to
the CPU. It has its own separate (6-pin) power connector (J2) and includes 12
( 4KX8) program PRO Ms. There is also some associated memory decoding
circuitry, as well as two 40-pin custom I Cs. These custom I Cs almost appear to be
processors but don't match any pinouts from the Motorola IC catalog. They
probably are just gate arrays for upper and lower memory enabling.
In addition to the ROM section, there is also a 6821 (1/0 port) which receives
all coin door switch information. This switch information all passes through a
buffering network and enters the ROM board through the ( IO-pin) J2 connector.
Please keep in mind the sound board enables (J4) are also generated by this
same 6821 1/0 port.
Failures in this board could be as varied as the functions of the board itself.
System lockup, coin door switch problems, or bad audio are all possible failures.
All program PRO Ms are checked during self test and are all mounted in sockets for
easy substitution. Taking care not to bend legs or mangle the sockets can help
prevent many failures from ever developing.
STAR*TECH JOURNAL/JANUARY 1983
3) Test points (on sound board)
TP1 - +12 volts (unregulated)
TP2 - -12 volts (unregulated)
TP3- Ground
TP4 - +5 volts
4) Fuses on sound board are both 4 ASB.
5) There is a self-test switch directly on the sound board itself (good for checking speaker
and amp). This switch, when depressed, will cause a recurring audio signal (similar to wings
flapping) until the game is reset
SELF TEST/OPTIONS
The usual detailed self test and option capabilities exist in "Joust". The self-test
switches are located on a bracket mounted on the coin door. There is a pushbutton
advance switch, a two-position pushbutton switch (auto up, manual down), and a
pushbutton high score reset switch. The advance switch merely advances through
each of the different categories of self test. The auto-up, manual-down switch
provides a method of skipping the diagnostics portion of self test and going directly
to the bookkeeping totals and game adjustments categories. With the pushbutton
switch depressed (manual down), the sequence of tests (using the advance switch)
will be ROM test, RAM test, CMOS RAM test, sound test, switch test, "color
RAM test", monitor test ( alignment and adjustments) bookkeeping totals and the
final category, game adjustments, before going back into the attract mode. With the
pushbutton switch in the up position (auto-up), the test will start ( using the advance
switch) with bookkeeping totals and then game adjustments before reverting back
into attract mode. This test mode is very thorough and·can really help narrow down
any game failures. Component failures are indicated by the 7-segment LED display
on the ROM board. For detailed explanation of the self-test feature, power-up tests,
and how to interpret the results of these tests, see the "Joust" instruction manual.
There is also a section on troubleshooting procedures which can be very helpful.
Please take note that there is also an advance switch located above the coin box
(lower front door). A collector can check audit totals without opening the upper coin
door.
OPTIONS - All options are established during the game adjustments section of
self test. The normal coin/credit combinations, and bonus settings options are
available. There is also a game difficulty setting, factory-programmed at 5. This can
be set from 0-9 with 9 conservative. This difficulty setting was especially critical in
"Robotron", and may be just as critical in "Joust". To maximize the earning of
"Joust", be sure to customize the options to each individual location.
CONCLUSION/COMMENTS
By now, the electronic system in "Joust" is very familiar to all operators and
technicians. This familiarity ( any standard system is better than no system at all)
makes repairs and game adjustments just all that much easier. This particular
NOTES
system, in the opinion of many service personnel, is the best. A detailed self test and
I) "Joust" uses 2532 and 2732 EPROM sets. Be careful when substituting PROMs.
a multi-board set (program ROMs on a separate board from the CPU) are the major
2) Schematic on ROM board shows +12 volts entering J12 pin 6. This +12 volts is also contributors to its popularity. For the operator, this game provides a two-line attract
shown supplying two custom chips (SA, 9A) pin 15. This voltage is not +12 but instead mode message, difficulty settings, and as an inducement for game play, the same
+5vdc (+12vdc does not even enter the ROM board). Please correct your master spectacular attract mode that is found on all games of this system. I felt nothing
schematic.
could top the "Robotron" attract mode (balls on outer perimeter rapidly changing
colors), but "Joust" comes close. (I like how it prints up the name "Joust" on the
INTERFACE BOARD - This board is hardly worth mentioning. It receives screen.)
The Service Department at Williams is usually very helpful (if you can get
switch info from the control panel and interfaces via a 20-pin ribbon cable to the
through on their 800 number) and the game documentation is almost complete. The
CPU board. Got a switch problem? This is the board to check.
games are shipped with a "drawing set" and instruction manual. Unfortunately, my ·
drawing set had no cabinet wiring diagram in it ( although it was shown in the list of
SYSTEM-AUDIO
The system audio is electronically nothing out of the ordinary. The sound board contents) and no parts catalog. It seems no one has a parts catalog, so don't feel
itself has its own separate microprocessor circuit featuring a 6808 microprocessor, badly - your distributor didn't take it out of your game.
As an aid to servicing, Williams has made numerous video cassettes on the
6821 1/0 port, 6810 RAM,and a 32K game program PROM. The audio amp
(TDA2002) is located directly on the board as well as a +5 (7805) regulator. All various components of their video system. These cassettes are available through
sound enables are generated on the ROM board and enter the sound board via the 9- their distributors, and even though I have never seen one, I am sure they would be
pin (J3) connector. Perhaps the most interesting feature is the sound board power very helpful to anyone servicing Williams' video boards. I have also heard that
distribution (see System Power). All voltages (+5, +12 unregulated and -12 Williams has designed some very specialized and costly test equipment for
unregulated) enter the 9-pin (JI) connector. What is most peculiar is that the + 5 repairing their boards, and this test equipment may be available to their distributors
enters on pin 3 which is not connected to anything on the sound board and that + 12 through some kind of lease, rent, or purchasing plan.
There appears to be very few problems with the "Jousts" which have been sold
and -12 unregulated voltages pass through fuses ( directly on the sound board) and
enter a bridge rectifier also on the sound board. Originally this circuit must have to date. There was a slight software problem in which players could defeat the
been designed for an AC input, but apparently for improved reliability (remember "unbeatable?" pterodactyl, obtaining higher scores and longer playing time. This
th.: bridge blowing out on "Flash" sound boards?). Williams decided to run problem only occurred on very early games, and was corrected by a ROM change
unregulated DC voltages to the sound board. As for the +5 volts going to an (#7 and # IO). I'm sure Williams has sternly reprimanded the "pterodactyl
unconnected pin ( + 12 unregulated enters an on-board 7805 regulator to supply + 5 programmer" and in the future, anything that is supposed to be "undefeatable" will
VCC for the sound board) the only explanation must be that this voltage could be be.
In essence, "Joust" is a good game from an established line of good games. It
used on some future design (new sound board?).
includes many improvements which Williams has added to this system with each
Audio Amp - TDA2002
successive game.
Volume Pot - SK, I watt
Speaker
- 6", 4 ohm, 3 watt
NOTES
I) Volume pot mounted on right side wall of cabinet (accessible through coin door).
2) Oip switches (2) on sound board have no effect