Galaxian Bootleg - Colour Issue

[andrewsm]

Had this board for a while and it was 100% but one day it just changed colours on the 30 point invaders from blue to whites. The bootup cross hatch also changed from white to yellow, Scores went yellow too from white.

Had a poke around a while ago but gave up and put it in pile for repair until now.

By chance found that if I ran board at 4.28V instead of 5V, the colours came back so set the voltage to 4.28 and blasted chips with a hot air gun. Found 6P (74LS377) would suddenly make colours change so stuck my tester on it and found that one of the colour outputs would get stuck high when the voltage went up or heat applied. When cool and at 4.28V, the output was fine. Looks like a bad device so ordered one up. Hopefully this will be it as rest of game plays and runs fine.,

 

[david_orton_2000]

Never tried a hot air gun technique, usually use the cold spray!

Thanks for sharing a repair log.

 

[Del Griffith]

Hey Mark, This the one you got from me last year? Is the chip you located branded sa by any chance? I remember it failed a couple of times when I first got it and each time it was one of those brand ic's. That's a nice trick with the hot air. Hopefully that is the fault and it's back up and running soon.