Picked up this board from
@DeLuSioNaL29 to take a poke at.
Game wouldn't display properly, looked like streaking red / bad sync and only showing blue.
Del told me that he had recapped it already and still not luck, so I assumed bad vias in the RGB area.
Got it under the microscope and found one trace that didn't connect to the via (via is still good, trace is dead), connected that direct to Ground with jumper and the red streaking disappeared.
Found 3 other vias that should have been connecting to each other through to a plane on the back of the board. None of those vias toned back to front, none of those vias toned between eachother.
I jumpered across 1 to 2 to 3 to connect them all to each other and the colors are back and looking great.
Last problem I had was inputs. Not noticeable on Galaga or Mappy because they are L/R only, but Xevious wouldn't go backwards (down).
When I flipped into test mode the selector would drop immediately to the bottom option as if the joystick down was pegged.
I could quickly force it to accept "switch test" by holding down P1 B2 as I was entering test mode and as expected it showed that P1 down was pegged.
Strange enough, sometimes in test mode it would l work, and then wouldnt and then it was tying P1 Down to P2 down so if I hit p2 down it would flip P1 down also.
I toned out jamma edge and P1 Down was a 5v, not grounded so I kept tracking.
Using DMM to follow the path and then Logic Probe I found there were two floating pins on Filter cap array that should have been tied to P1 down and P2 down.
Reflowed with a ton of flux and new solder, and it seemed to work.
Then it started flaking out again and was tying P1 to P2, so I cleaned up the old flux and solder site the best I could and then it stopped tying them together and are working independantly.
Only problem I seem to have left now is that P1 down does not flip right away, you have to hold the direction and after around 1/2 second it will flip, all other inputs flip right away..
With some intel from
@DogP I will be checking the Filter array and resistor pack just before it to see what I can find, but overall, this is 98% playable and back from the dead.
Will report back to close this one off.
**Sidenote, 2 player galaga on this board where you can both play at the same time is cool AF.