A-H / I-P / Q-Z / 0-9
Arian Mission Asteroids Astro Blaster Bad Dudes vs Dragon Ninja Bomb Jack Breakout Bubble Bobble Dark Mist Donkey King Double Dragon Exzisus Finalizer Gladiator Green Beret


Arian Mission
Fault
Solution
Fire input (Button 1) permanently grounded. Ship fires constantly during game play. The input of the 74LS367 (pin 4) at location H10 was shorted to GND. Replacing the IC fixed the fault.

Asteroids
Fault
Solution
Fire button not working.. The inductor (L13) on the switch input had gone open circuit. Replacing the inductor fixed the fault.
Bad vectors. Vectors very 'messy' and wobbly. The +5V regulator (VR3, 7805) was outputting approximately +11V. Replacing the regulator fixed the fault.

Astro Blaster
Fault
Solution
Player shot & enemy shot sounds missing. The CD4011 @ U25 on the sound board is common to both of the laser sounds and was found to be bad. Replacing this IC fixed the fault.
Invader 4 sound incorrect. The CD4024 @ U28 on the sound board was getting a clock from the 555 timer but the output was incorrect. Replacing U28 fixed the fault.

Bad Dudes vs Dragon Ninja
Fault
Solution
Foreground graphics faulty - top of screen = bottom of screen. Two tracks from A9 & A10 on the SRAM to one of the custom chips were broken. Repairing the tracks fixed the problem.

Bomb Jack
Fault
Solution
Stripes of background graphics missing and replaced by solid coloured blocks. The output of one of the background video shift registers (74LS194 @ 7J on the board 5803A) was stuck low. Replacing the IC fixed the fault.

Breakout
Fault
Solution
The score is repeated all the way down the screen. The output (Pin 12) of the 7427 at location M8 was floating. replacing this IC fixed the fault.
The borders are missing. Part of the 7427 at location H3 is used to combine the individual parts of the border. Pin 12 is the result but was found to be floating. Replacing the 7427 at H3 fixed the fault.
The paddle is doubled (one on top of the other) The 16H input to the paddle summing circuit (7430 @ K3) was not being included in the equation. Replacing the 7430 at location K3 fixed the fault.
All of the numerals are displayed as '8's. The outputs of the BCD to 7-segment converter (7448 @ J5) were bad. Replacing the IC fixed the fault.
The first digit of player 2s score is '8'. Output L2 of the player 2 score counter (9310/74160 @ L6) was floating. Replacing the IC fixed the fault.
The paddle is always a solid bar that extends across the entire screen in game mode, not just in attract mode. The /Attract signal is used to display the paddle as a solid bar during attract mode. The paddle signal is NANDed with the /Attract signal by the nand gate (74LS00) at location C3. The /Attract input was being corrupted by a bad input pin (pin 13 of C3). Replacing the 74LS00 at C3 fixed the fault.
The ball served display does not increment. The OR gate at D2 is used to generate the CP signal which clocks the ball served counter. The OR at D2 (7432) was found to be bad and after it was replaced the ball served display incremented.

Bubble Bobble
Fault
Solution
Completely dead, not even composite sync. I first checked the CPUs. there are 3 Z80s on the top board and none of them had a clock. The clock circuit is on the bottom board and is made from a crystal and a 74S04. The 74S04 had no power. The chip had been socketed but the Vcc pin was broken off. Replacing this chip fixed the clock problem and led to the fault below.
Dead with garbage on the screen. I first checked the reset pin on all 3 Z80 CPUs. The reset pin was constantly low. I traced the reset signal to an AND gate (74LS08). One of the inputs was high and the other was toggling every couple of seconds but the output was held low. Replacing the 74LS08 fixed the fault.

Dark Mist
Fault
Solution
Incorrect and flickering colours. One of the palette rams (6116 skinny dip @ location A10 on the main board) was bad. replacing this IC fixed the fault.

Donkey King
Fault
Solution
Dead with garbage on screen. If I manually reset the Z80 by shorting the RESET/ pin to GND, the board would burst into life. RESET/ was being generated by an RC circuit which passed through a 74LS08 (AND) to the CPU. The 74LS08 was found to be working. Replacing the Capacitor (10uF) in the RC circuit fixed the fault.

Double Dragon
Fault
Solution
Too much red in picture. I traced the red video signal back through a 74LS273 to the palette ram (2016 @ 6B-D on the top board). D2-D3 of the palette ram was stuck at about 2V. Since the palette ram has already been written and should now only be being read from (this was verified by checking the output enable of the 74LS245 buffers connecting the ram to the bus) I concluded that the ram must be faulty. Replacing the RAM fixed the fault. NOTE: On this particular bootleg board there are 2 mods which need to be added to the ram. Pin 21 needs to have a pull-up resistor added and pin 4 needs to be connected to the via next to it.

Exzisus
Fault
Solution
No Sound Audio was present at the input of the TL074 op-amp but was not present at the output. Replacing the TL074 fixed the fault.
Some of the colours are incorrect. I first checked the palette ram (2016 @ 6B-D on the top board) and found that pin 3 was stuck at 0V. I traced the signal to a 74LS153 (Dual 4-line to 1-line data selector/multiplexer). The strobe input (/G on pin 15) was sat at about 2V. The strobe pin was wired to GND but the track must have had a break in it. Wiring the stobe pin to GND fixed the fault.
No Music Replaced dead MC4558 at location 6Y on the top board.
No Sound Effects Replaced dead MC4558 at location 6U on the top board.

Finalizer
Fault
Solution
Jailbars on sprites. One of the sprite buffer RAM chips (4464 @ 12F) was found to be faulty. Replacing this IC fixed the fault.

Gladiator
Fault
Solution
Colours Wrong. The Blue and Green video signals did not drop below a certain level so the screen had an orange tinge. The outputs of the palette RAM (pins 8,9,13-16 of the 2116 at location 8B) were permanently high during active video. Pins 10 and 11 however seemed OK. the common factor between the high pins is a 74LS367 (Hex Bus Drivers) at location 7B. Replacing this IC fixed the fault.

Green Beret
Fault
Solution
Every other line of the sprites are transparent. One of the AM2148 sprite buffer RAM chips was found to be faulty and was replaced. This fixed the problem.