Ms Pacman Troubleshooting Tool

During the testing phase at GLS1 Electronics, different sections of the Ms Pacman circuit are tested by using these interface screens.
    They have been compiled together into one executable file, which is downloadable at the bottom of this page. This file runs under Windows Xp / Me / 98Se. The statements in the program code involving actual communication with the hardware interface board / circuit board under test have been removed. However, the troubleshooting information has been retained, and is accessible by viewing and using the various interface screens.
   The controls used to adjust the different variables required for each test are still enabled, and each simulation screen will provide the user with a working example of each interface used. This file is provided free, and is only offered for those who may have interest in how the testing and repair service is performed at GLS1 Electronics.

Real-time measurement of inputs

The purpose of this interface is to display all dip switch positions, coin, and control panel inputs. Additionally it will show which pins are activated on the 74LS367's ref (8D, 8E, 8F, 8H). These chips are responsible for reading input from the edge connector and the dip switch at location 9D.

In the reference mode, this screen can be used for troubleshooting purposes. Positioning the mouse above the different labels will show which 74LS367 is used for each input, as well as show which pin on the IC is involved. It will also display the discrete components used on the input, for example, hovering over pin 2 of IC 8D will cause a dialog box to appear stating: "Dip switch #5. Resistor Pac RM6 1K ohm to +5 volts.", or Player 1 Up will show the position on the edge connector which is involved.

More information on running this test


Diagnosing address decoding section of the circuitry :

Address decoding involved with 74LS138 chip (7J) used during reading of input ports DipSw, In0, In1. Also used in conjunction with output ports 74LS139 (7M) write function for moving character and sound circuitry. Selecting function label causes conditions on circuit board to react identically with what is displayed. Adjustment of the slider bar can be used to increment through all of the possible binary conditions which exist in this area of the circuit.

In the demonstration version, this screen can be used for reference purposes. Positioning the mouse cursor above In 1, for example, will display "Reads player 2 , and test switch information from edge connector", or hovering above pin 10 of IC 7J will display "Connects to pin 1 of 8H and pin 1 of 8F."

Troubleshoot individual address lines from the Cpu to Ram chips 2114

Address bus driver tests for the two 74LS367 chips (6S, 6R). Used for isolating address bit errors with relation to the six 2114 Ram chips. Individual control of pins on the IC's, unique conditions (only one high or low) are selected by clicking on the corresponding label. Hovering the mouse cursor over a pin number on an IC picture will cause a dialog box to open stating where where else it connects in the circuit.
The slider bar adjustment may select any address in the range: 4000 - 4FFF. This interface can also be used to verify the operation of IC 74LS139 location 5L. For example, clicking on pin "9" will cause pin 9 to pulse low on that IC, enabling 2114 Ram chips (4K, 4N) on the circuit board under test.


Test the sound circuitry without the game having to be played


7489 music and sound tests. Each of the 16 locations of the 7489 chip can be programmed with any one of the 16 possible variables, by selecting the appropriate slider bar for that location. Most combinations of the slider bar adjustments yield bizarre sounding results. However, during troubleshooting this area of the circuitry, single pins on the 7489 IC can be targeted and followed through using an oscilloscope.

The sound and reset check boxes, which control the 74LS259 chip shown below, must be selected in order to hear the sound during the tests. Closer examination of this process, as well as control over these events, is shown:


Completely test all functions of IC 74LS259 8K addressable latch


74LS259 in-circuit testing. This screen is designed to test and verify the operation of the 8-bit addressable latch at 8K. This chip controls the signals for "sound on", flip screen", and to pulse the coin counter. Every output of this device can be verified by adjustment of the vertical slider bar, and a combination of the check boxes.

For reference purposes, this example will show the sequence of events required for the various operations in this section of the circuit, and can be used to understand the function of a 74LS259 integrated circuit.


Adjust position of the moving characters :


Problems in the positioning of the moving characters can be diagnosed by direct communication with the two 7489 chips at 3F and 3H. The 74LS161 counter chips at 1E and 2E parallel load these starting location values (d0 - d7, longer slider control) on their inputs to determine the coordinates of each one of the moving characters (ab0 - ab3, shorter slider control)

Address range: 5160 to 516F, R/W mode: (Write at Wr 2), an extension from the addressing decode module, shown above.


Troubleshooting information included on separate sections of PCB


	This screen is layout diagram of the various sections which make up the Ms Pacman logic board. At the present time, information is being entered into the program which describes each section, and possible symptoms which may occur if that section fails.

The latest version of this software example is dated 03-03-2004, version: 03032004-910Am, and is available here: Download troubleshooting tool

Contact me at greg@gls1electronics.com for more information, or for help to troubleshoot your Ms Pacman PCB problems.

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Troubleshooting Tool
Designed for Ms Pacman PCB's
Computer Aided Testing System