Ok now i removed the 2x vrams(2114) from location 3F and 3H and tested them in my pacman board and 1 failed and other one was ok. 
fitted two new srams and powered up...............................................
Well what can i say
,good news is the game runs and plays but as you can see all sprites and tile graphics are a mess.
This fault had to be in the sprite and tile circuit ,i suspected possibly bad sprite and tile roms,so these are located at 1L and 1J,
i dumped these and they romident ok.Had a hunch it may be a addressing issue so i started scoping all the 74ls157 in the sprite/tile circuit and i came across a 74ls157 at 6J,pin 7 output was stuck high.
replaced with a new ls157 powered on and.............................................
Ooooo yes,galaxians live again!
put in a credit and played it with no issues except the fire sound was missing and also the explosion sound when you get destroyed.
Managed to trace this fault in the audio circuit.
from the schematic there is a bilateral quad chip at 7T,there was no output from pin 3 and 10 .
replaced with a new one and all sounds were back,soak tested the game for 2 hours and all was well.
fitted two new srams and powered up...............................................
Well what can i say
,good news is the game runs and plays but as you can see all sprites and tile graphics are a mess.This fault had to be in the sprite and tile circuit ,i suspected possibly bad sprite and tile roms,so these are located at 1L and 1J,
i dumped these and they romident ok.Had a hunch it may be a addressing issue so i started scoping all the 74ls157 in the sprite/tile circuit and i came across a 74ls157 at 6J,pin 7 output was stuck high.
replaced with a new ls157 powered on and.............................................
Ooooo yes
,galaxians live again!put in a credit and played it with no issues except the fire sound was missing and also the explosion sound when you get destroyed.
Managed to trace this fault in the audio circuit.
from the schematic there is a bilateral quad chip at 7T,there was no output from pin 3 and 10 .
replaced with a new one and all sounds were back,soak tested the game for 2 hours and all was well.
