JAMMA Pong Board
Revitialize This Arcade Classic with this simple build-it yourself project!

by Spike Tsasmali

  Difficulty=2 Howls

Beep-Boop-Beep-Boop-Bup. The sounds of Pong. It has been 40 years since this classic video game has been released and it still attracts a nostalgic crowd. But where can you go to play one? The REAL Pong? Well, not many arcades still offer this timely piece. But that can all change.

You can now build this simple PONG game board and plug it into any JAMMA cabinet and have the Classic of all Classics! Based on the genuine General Instruments AY-3-8500-1 TV Game Chip (which is remarkably still available), this is the closest thing to the original PONG you can get without being the real thing!

JAMMA Pong Project Board
(Full production board is slightly different in appearance)

Remembering the Old Days

The original PONG game was a basic black and white TV tennis game and used two rotary potentiometers to control the "paddles". It also used a single pushbutton to start a two-player game (the original PONG was designed to be a 2-player game. Later versions included a single player.). The game finalizes out with a coin switch and a speaker.

Although the push buttons were never a major problem, the rotary potentiometers were constantly a nightmare for the operator. These controls would wear out or become dirty and once damaged the paddle would "fly" across the picture instead of moving smoothly. Sometimes the paddle would disappear totally.

Early versions of the game were built using a modified black and white television, typically an Admiral desktop model. These televisions were also difficult to maintain and did not have much of a life. Later versions of the game used Motorola black and white monitors, which were a huge improvement. Also, some PONG games had a green "overlay" which covered the picture tube. This was used to color the picture "green" as to appear to be a "computer" image. The original PONG was never manufactured as a full "RGB" color game.

PONG as a JAMMA Game

Several changes have been made to facilitate PONG as a JAMMA game. The two most obvious changes are:

  • Joystick control
  • Color picture
  • Joysticks now replace the horrible rotary controls used on the original game. And the game is now in COLOR. Player 1's paddle (on the right side for PONG) is GREEN, Player 2's paddle is BLUE, the TENNIS COURT is YELLOW and the ball is WHITE. GAME OVER and ATTRACT MODE screens are in RED and the TEST MODE is multi-colored.

    Game Over Screen Credit Screen Start Up Screen
    Skill Select Screen 1 Player Practice Game 2 Player Game

    One and two player games have also been included. Depending on coin settings, after inserting coin the player(s) may select a one or two player game. One player plays "practice" and trys to keep the ball in play for as long as he can. Two players compete against each other, scoring when the opposing player misses the ball. The game runs until a score of 15 is reached.

    Due to logistics of using the AY-3-8500-1 chip, this JAMMA game project is based on timing and useage of controls to determine GAME OVER status. Therefore, once a score of 15 is reached, the ball may still serve and the paddles may still move (just like the original) but you cannot "play" the game. After a short wait (about 6 seconds) the game will resume a GAME OVER condition and will be in the ATTRACT MODE. While in the ATTRACT MODE, the game does not serve and the paddles are held in the center position.

    TEST mode has also been added to facilitate adjustments. Monitor test patterns, switch inputs and paddle control test are all included on the TEST menu.

    How it Works

    The Schematic Diagram for the PONG game board is shown in Fig. 1 and can be Downloaded as an EasyTrax PCB file from the Lupine Systems Download site. This PCB file is BEST PRINTED at 85% full size (it fits perfectly on a single sheet of paper when printed at 85%). To do this using EasyPlot, first load the pongsche.pcb file, then use the Setup, Printer function. Select SCALE then enter 85. Remember that SCHEMATICS are on the 1 MID LAYER so be sure you toggle ON the 1 Mid Layer or you will get a blank screen!

    Schematic of JAMMA Pong Board

    The PONG game consists of three major components -- the PIC processor, the On Screen Display Controller (OSD) and the heart of the project -- the AY-3-8500-1 TV Game chip.

    Master clock is generated by oscillator module U3. The 8 MHz Master Clock is used by the PIC as the main processor clock. The PIC divides this clock by 4 resulting in a 2 MHz signal at Pin 10 of U2. This 2 MHz clock is then used by the Game Chip as it's system clock. The 8 MHz Master clock is also used directly by the OSD chip as the pixel clock.

    Switch inputs from the JAMMA control panel are filtered and pulled-up by resistors R9-R15, C1-C17 and network RP1. These filtered inputs are then buffered by U11, a 74LS541 Octal Bus Buffer. The outputs of the 74LS541 then go directly to the inputs of the PIC processor for processing.

    Joystick inputs are processed through the PIC processor and are used to control two E-pot potentiometers U9 and U10. Pulses from pins 12, 13 and 14 of processor U2 toggle UP and DOWN the resistance values of these electronic pots. These E-pots are used to replace the rotary potentiometers originally used on the PONG game.

    The Game Chip is used as the Master Video Source and generates separate video outputs for each of the components visible on the screen, as well as composite horizontal and vertical timing. This composite sync signal is separated into non-composite sync by integrator U5,D5,R1 and C7. Vertical sync is separated from the composite sync and is then fed to the Vertical Timing input of the OSD chip U4 at pin 16. Since the composite sync coming from the Game Chip is digital, the horizontal sync component will be constant and can be used as the Horizontal Timing signal needed by the OSD. Therefore, composite sync appears at Pin 17 of U4 as Horizontal timing. The composite sync is then re-buffered and routed to Pin "P" of the JAMMA edge connector.

    The separate video signals generated by the Game Chip are mixed together to form the RGB color scheme used by this project. Video is mixed using the XOR gate U8. Finally, video generated by the OSD chip is overlaid onto the video from the Game Chip by multiplexer U7 and is under the control of the Overlay Blanking signal generated by the OSD chip U4 at Pin 14. Mixed video is then routed to the JAMMA edge connector.

    Audio is generated by the Game Chip. Sound is amplified by amp chip U12 and is routed to the JAMMA edge connector.

    DIP SWITCH settings are both processed and fixed. Two of the DIP switches are processed by the PIC and are used to select pricing options. The other two are related to the Difficulty Level and affect the Game Chip directly. Diodes D1,D2 and D3 are used to specially connect the individual inputs used by the Game Chip so that a simple DIP Switch setting can be made to control the game difficulty.

    Building The Project

    Since this project will create a JAMMA edge connector, the use of a printed circuit is HIGHLY recommended. The PC board will be double- sided and will require soldering on BOTH SIDES. This poses a problem for chips so care must be taken when assembling.

    Tip. When assembling double-sided boards with chips, use Machine Tool sockets. First solder ALL pins on the Solder Side, then single out the ones you need to solder on the PARTS SIDE, heat from the SOLDER SIDE the pin, then CONTACT solder the pin lead to the TOP LAYER using reflow techniques.

    What You Will Need

    The complete list of parts for the JAMMA Pong Project is given in Table 1. You will also need common shop tools, solder, PC board materials, etc.

    Before you can begin the project, you will need to download and install EasyTrax CAD software. If you are not already familiar with EasyTrax, then please take the time to read through the Tutorial on how to use EasyTrax.

    You will also need to download the JAMMA PONG Project Schematic Diagram and Printed Circuit Layouts. The schematic diagram is located on the 1 Mid Layer of the layout file (read the Tutorial for more information).

    If you need help with making PC boards, please read the article, Making PC Boards.

    Table 1.
    Parts List for JAMMA PONG Project

    .1uF NPO or Z5U Bypass Capacitor22C1-C19,C21-C23
    470uF/16v Radial Elec1C20
    2.2uF/35v Axial Elec1C24
    47uF/16v Radial Elec1C25
    1K ohm 1/8 watt3R1,R2,R8
    220 ohm 1/8 watt12R3-R6{R7},R9-R15,R22
    10K ohm 1/8 watt5R16-R18,R20,R24
    5K ohm miniature PC mount audio taper POT1R19
    1.2 ohm 1/4 watt2R21,R23
    1K x 9 Bussed Resistor Network1RP1
    TIP-122 NPN Darlington Transistor1Q1
    AY-3-8500-1 Game Chip (GI)1U1
    PIC16C62A Microcontroller (Microchip)(see text)1U2
    8MHz Oscillator Module1U3
    uPD6145-001 TVDC/OSD Chip (NEC)1U4
    74LS00 Quad NAND Gate2U5,U6
    74LS157 Quad Data Selector1V7
    74LS86 Quad XOR Gate1U8
    X9C104P E-Pot (Xicor)2U9,U10
    74LS541 Octal Buffer1U11
    TDA-2002 or TDA-2003 Power Amp Chip1U12
    4-POS DIP Switch1U13
    Socket for U1, 28 pin DIP Machine Tool1*
    Socket for U2, 28 pin Skinny DIP Machine Tool1*
    Socket for U4, 18 pin DIP Machine Tool1*
    Heatsink for U121*

    IMPORTANT NOTE: The PIC16C62A is an obsolete component. You may substitute a PIC16F73 if you add these three lines of code to the assembly file before you re-assemble and program your device:

    Insert this line at the very beginning of the code on the first page:

    Find and locate the section of the program with the title START. Insert these two lines BEFORE the first BANK0 statement:

    	MOVLW	0x06


    After you have downloaded the PC Board Layouts, burn and etch a PC board for your project. If you need help making the PC board, read the article, "Making Printed Circuits".

    Carefully assemble the PC board according to the Component Placement diagram provided on the 1 Mid Layer of the PC Board layout file. Remember this board is a DOUBLE-SIDED board and will require soldering on both sides of the board. Via holes will have to have a small wire inserted in the hole and then soldered on both sides. This may take some practice if you are not accustomed to having to do this. Use of machine-tool type sockets is recommended for all socketed chips because these type sockets make soldering on the top layer easy. Simply solder the socket completely on the SOLDER SIDE first, then go back and heat each pin you need to solder on the TOP layer by touching the tip of your soldering iron to the pin on the BOTTOM of the board, then let the heat conduct through the pin to the TOP side. Apply the solder to the pin of the socket on the TOP side and use the pin's heat to solder it to the circuit pad.

    Once you have completed assembling the PC board, you will need to Download and PROGRAM the PIC microcontroller with the software pong.asm. This is an ASSEMBLY FILE and will require you to run it through a Microchip PIC assembler to create the .HEX file needed to program the PIC. You can download a copy of MPLAB FREE from the Microchip Technology website. When you are ready to program, set your programmer to program the PIC with Brown Out Detect OFF, Code Protect OFF, Power On Timer ON and Oscillator to RC (PIC microcontrollers will accept external clock in the XT or the RC mode, but will only provide the fclk/4 timing signal in the RC mode). Once programmed, install the PIC in the socket for U2.

    The JAMMA Pong board is now complete and ready to play!

    Setting the DIP Switches

    DIP SWITCH Settings for PONG1234
    1 Coin 1 per Player
    (Each player pays to play)
    1 Coin per Game
    (Single credit, but
    2 Players can play)
    Free PlayONOFF
    Paddle Size in Expert Mode
    Ball Reflection Angles
    4 AnglesON
    8 AnglesOFF

    Operational Notes

    Here are a few things you will need to know about the operation of the JAMMA Pong board.

  • Since the game is based around the original General Instruments AY-3-8500-1 chip, which was originally designed for home TV tennis games, the GAME OVER system is based on time and not "actual" events. Once a score of 15 is reached, the game will no longer count score nor will the paddles bounce the ball BUT the player will still be able to move the paddles with the joystick. Early versions of the original PONG game also did this so this is a mock of the original. GAME OVER is based on TIME, and as long as a joystick is moved, the GAME OVER timer is constantly being reset. Once the joysticks come to a rest, the GAME OVER mode will appear within a few seconds.

    This time-out feature will also activate and end the game if the player deliberately gets the ball "stuck" bouncing back and forth between the paddle(s) and the walls in a never-ending bounce-back and forth situation.

  • If there is credit AND the Start button is pressed during a game, this will initiate the GAME OVER sequence and hence issue a RESET. This is similar to the RESET button on the home game console BUT with a coin switch. Here's how it works..If there is 1 or more credits, then pressing the 1 Player Start will end the current game and allow the player to add more coins for a 2 player game, or start another 1 player game with the credit currently on the game. Having 2 or more credits will enable the 2 Player Start to also end the current game and begin a new one.
  • Credits may be added to the game at anytime EXCEPT when the Skill Select screen is showing. Adding extra coins during game play will not affect the game or game play in any way.
  • The paddles may not be perfectly aligned in the center during GAME OVER mode. This has no effect during game play. However, if this is a nuisance to you, you may "tweak" the paddle positions by replacing resistors R16 and R17 with 20K pots. This way you can fine tune the positions.
  • Due to the nature of this game, the Player 1 and Player 2 joysticks are reversed. Unlike regular modern JAMMA games where Player 1 is on the LEFT side, PONG places Player 1 on the RIGHT side. So to align the joysticks to the paddles on the screen, the joysticks are reversed. Therefore, it is necessary to install this board in a DUAL joystick JAMMA cabinet.

  • Professional PC board is available for this project. Professional PC board has true-sized JAMMA edge connector, fully etched, drilled, plated-thru holes with silk screen legend and green solder mask. Contact WOOFY for more information!

  • Lupine Systems also stocks the AY-3-8500-1 PONG chip. Contact WOOFY for more information!

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    A Part of the Blue Woof Group