Working Ms Pacman Screen
Working Ms Pacman Game screen
Vertical pieces of maze scroll across screen from right to left.
2R Pin 11,12,13,14
.
Fast moving Vertical Lines From top to bottom. Caused by shorting 6 Mhz clock signal.
Chip 3D pin4 or 13
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Horizontal bars across screen size will vary.
3N pin 9 high
Fast 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 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.
Blue 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