Galaga blue screen. Help.

[lost in cables]

Hi, running Galaga, main play screen(playfield) blue? any ideas where to start? any advice would be great where to start looking.
top and bottom of screen fine just live playfield area blue.

 

[Lurch666]

Does it play blind?

 

[lost in cables]

Yes, plays blind, game play sound all good fire and death 😄

Been probing about on the board but can’t see anything obvious. Any idea where the background sprites are done on the board?

 

[Lurch666]

Checking scematics if it's playing blind then I'm assuming one of the inputs to 4M or 5N is maybe stuck.

 

[lost in cables]

Thanks, will look at them proms/ are and let you know. Think they are customs 👎

Star.

 

[Lurch666]

Yep 4M is a custom but 5N is a prom so that's replaceable.
I'm assuming one deals with top and bottom of the screen and the other the main play area and that's the one with a problem.
A video probe would help here.

 

[qjuk]

Are you running a high score save kit on this?

If so, remove the kit, put back in the Z80 and original game eproms on the board and see if that is the problem.

 

[Lurch666]

So it's definitely the 4M custom?
Did you check all the inputs?