Pacman working screen

Working Ms Pacman Screen


Ms pacman working game

Working Ms Pacman Game screen


Ms pacman vertical maze

Vertical pieces of maze scroll across screen from right to left.

2R Pin 11,12,13,14


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ms pacman horizontal lines

Fast moving Vertical Lines From top to bottom. Caused by shorting 6 Mhz clock signal.

Chip 3D pin4 or 13


ms pac hirozontal line 2Horizontal bars across screen size will vary.

3N pin 9 high


ms pacman scrambled screenFast moving short vertical lines covering the screen. High pitch squeal coming from monitor. Caused by shorting 6 MHZ clock signal to other chips. Also caused by PCB frequency pot not adjusted.

2B shorted to 6MHZ clock signal to pin 14 to pin 9, 10, 11, 12,13,or 15 or 2A short to pin 14 to pad next to it.  OR 1E, 2E, short Pin 2 to  1,3,4,5,6,8.


No Sync For the Monitor .

2S pin 11 Sync low

Check 2R, 2S


 fast moving vertical lines pacmanFast moving vertical line moving top to bottom with two columns. Also high pitched squeal coming from monitor.

Chip 2A,2B, 2C, 2D 6MHZ clock signal pin 14 is grounded.

Chip 4B pin 11 short to 3B pin 9-14


Distorted Maze

6MHZ clock signal short from chip 4B pin 11 to 3B pin 15.


pacman blue tornadoBlue tornado moving quickly from right to left. Can also be solid blue block with score and credit ok.

3A bad or missing.

3A Pin 9 short to pin 13.


 Will not boot. Orange garbage on the screen. making a repetitive noise on and off.

4R pin 12 short to pin 15.


 Random Garbage on the screen. Problem with 5F ROM. Dip switch 8 is on. this will freeze video at power up.


Random Blocks of garbage on screen

Problem with 5E ROM


 Board will not boot. Screen cover with zeros. Top row changes to different letters and a single object changes in the center as the board tries to boot.

4K, 4N video ram bad


 Board will not boot. This is simply one of the screens it shows when trying to boot.

4L video ram bad


 Just a few random objects on screen.

4M video RAM bad


4P video RAM bad.


4R video RAM bad


Light red haze over the screen.

Signal from 4A pin 11  to 3A, 3B pin 11 high.

Signal from chip 3B to pin 9 to 7F is high


 Red Background

Signal from 4A pin 12  to 3A, 3B, pin 14 low

Signal from 3B pin 12 to 7F pin 10 too high


 Red background between score and credit. No characters on screen.

3A pin 9 short pin 11, pin 14.


 Red Screen.  Block characters, score and credits.

5A removed


Green Haze

Most likely caused by your monitor.  If you have a known good monitor then check green output edge connector 16 is high.


Red Haze

 Most likely caused by your monitor.  If you have a known good monitor then check red output connector T is high


Blue Haze

Most likely caused by your monitor.  If you have a known good monitor then check Blue edge connector Pin U is high


 Graphics are blocks. Characters Ok

5E bad or removed


White Background, Red maze, blocks behind characters.

5C removed

5A pin 14 high


Pink background, pink maze, red maze outline, blocks behind characters. Yellow behind score and credit.

5B removed

5A pin 11 high


 Entire screen blue.  sound and games still function

Chip 3B bad or removed


Blue Box. Black box where characters are. score and credit ok.

A 74157 was placed into socket 3A instead of a 74158.


Red or yellow box. Sounds OK

2C pin 7 short to pin 5,6,8 yellow

3D pin 6 low yellow

2D pin 7 short to pin 5,6, 8 red.

3D pin 3 low red.


Red or yellow box on screen. score and credit Ok.

2C pin 7 short to pin 1 yellow

2D pin 7 short to pin 1 red


 One bar on top half of screen. score is OK.

2C short pin 15 to 9 yellow

2D short pin 15 to 9 red


Two bars on screen

2C short pin 15 to pin 10 yellow

2D short pin 15 to pin 10 red.


 Four Bars on screen

2C short pin 15 top pin 11 yellow

2D pin 15 short to pin 11 red


8 Bars on screen

2C short pin 15 to pin 12

2D short pin 15 to pin 12 red.


 16 Bars on screen

2C pin 15  short to pin 13 yellow

2D pin 15 short to pin 13 red

if 32 bars on screen then 2c pin 7 is short to pin 2 yellow

or 2D pin 7 short to pin 2 red

If 64 Bars then 2C pin 7 is short to pin 3 yellow

or 2D pin 7 is short to pin 3 red.


128 bars on screen. hazy shade of yellow or red over entire screen

2C pin 7 is short to pin 3 yellow

2D pin 7 is short to pin 3 red.


Entire row of characters cloned from left to right

2A, 2B, 2C, 2D, pin 1 chip is grounded enabling the chip all the time


All characters are chopped in half with their base on top of their head and stuck on the top row of the game maze under score.

1E or 2E bad or removed

1E pin 15 shorted to pin 16

If characters are flashing then 2E pin 7 and pin 10 are too high


 No characters on screen. Dots can be seen eaten caused by interfering or grounded databus RA0 thru RA5

These can be found on 2A, 2B,2C,2D  pin 2,3,4,11,12,13 or 1E pins 11,12,13,14, or 2E pin 13,14.   2B is too high, or pin 2,3 or 3,4 or 4,5 shorted. 2A pin 12 & 13 shorted. 2E short pin 7 to p10. 1E 2E pin 15  shorted to 11,12,13,14.

3D bad or removed.

3A, 3B pin 1 low

3B pin 1 short to pin 8.


All characters stuck in lower central corner of screen

1E or 2E pin 9 is too high


All characters look like their being transported. characters become lines from top to bottom of screen still move from left to right.

1E or 2E pin 9 grounded or shorted to pin 15.

1E pin 9 shorted to 11-15


Characters move over the maze lines and act jittery

1E pin 6, 2E pin 2, 3,4,5 or 6 databus Dr3 tru DR7

shorted or high


 Fine horizontal lines thru maze and characters

2B pin 4 short to pin 7


Boxy maze with no characters

1E or 2E pin 1 short pin 2,3,4,5,8

1E pin 15 short to pin 10


Medium Horizontal wash board black lines thru maze

2B pin 3 short to pin 7


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