This page shows some of the tests performed at GLS1 Electronics while servicing Galaga and Ms Pacman logic boards. Testing different sections of the board under test is accomplished by selecting the appropriate screen, which has been designed specifically for that purpose.
The Hardware Interface Device is set to the Z-80 type microprocessor for these tests.
Here is an example of testing inputs and dip switches on a Ms Pacman PCB, using software designed for this particular section of the board. This phase of testing is viewable at the following link :
Check Dip Switch and I/O Ports.
Sound and music tests are performed.
This interface is designed for the sound section of the Ms Pacman PCB. Every addressable location in the sound ram can be manipulated and tested. This is useful, as there is no need to attempt troubleshooting while trying to play the game. Ms Pacman Sound Tests.
Verify proper operation of pins on individual IC's
This method of troubleshooting enables pinpointing of the exact cause of failure on the circuit board under test. An example of targeting two 74LS138 chips location 1P and 2P in the address circuitry on a Galaga Cpu :
Testing the 74LS138 Chips on a Galaga CPU Board.
Video tests are performed
Visual and electronic tests, including text, moving character, scrolling, and color background. An example of loading a test pattern into Galaga video RAM is viewable by following this link:
Load Grid Pattern to Galaga Video Board.
Tests are run continuously to capture intermittent occurring problems
Groups of tests are performed while vibrating / flexing board sets to prove long-term reliability. This phase of testing is logged, and the results are scanned for errors. Error analysis to determine failure.
All program chips are tested using master data reference files.
All program revisions are supported. Any conversion type done to the hardware is supported. Tests are run thousands of times, and scanned for errors. An example of testing the program on a Ms Pacman PCB is shown on this page: Testing for the correct program.
NMION, Mod0, Mod1, Mod2, Reset, IRQ1 and IRQ2
These operations are all checked, and confirmed in this example of examining the function of the 74LS259 chip location 3C on a Galaga CPU board:
Testing the 74LS259 chip, location 3C, Galaga CPU board
Reviewing the Galaga dip switches in real-time
The 2 dipswitches on the Galaga Cpu board located at positions 6J and 6K are checked and verified for correct operation. This measurement shows the switches change position as the switches are activated on the board.
Examine Galaga dipswitches.
Testing the star generation circuitry on a Galaga video PCB
The star field pattern originates from the custom 05 chip located at 4M on the video board, and is controlled by the 74LS259 chip location 5K. This addressable latch can be completely controlled using this interface, which allows adjustment of the star speed and direction, as well as the screen flip for player 2.
Star scrolling and screen invert.
Addressing troubleshooting referred to by IC location and pin number
Tracing the integrity of the address bus by selecting an individual address line to verify, using an oscilloscope .These tests can be cycled continuously, and will show as a stream of pulses:
Address bus tests, Galaga & Ms Pacman.
Using the interface tool
The same tests can be performed using this page of the troubleshooting tool , which shows a better visual representation, and allows pointing and clicking on the desired pin number on each chip.
Troubleshooting tool designed for Ms Pacman
Testing the 2114 ram chips on a Pacman-type board
The testing of the individual ram chips on on Pacman type board is shown in this example. If an addressing error is suspected, the above interface screen can be called upon to troubleshoot the individual buffered address lines. If data bit errors are experienced, individual data lines can be diagnosed by writing binary numbers which have exclusively one hi or one low bit.. (00000001, 00000010, 11111011, etc).