1942 Help Required

[BubNotBob]

I have a Capcom 1942 original PCB, it has a problem where all the foreground sprites like the players plane and enemy planes are stuck at the bottom of the screen, the Y coordinates are not being correctly mapped. The great thing with this board is it has great schematics, but I am going around in circles (unlike the sprites in the game ) pinpointing which part of the board to look at. Could anyone with more technical experience or 1942 knowledge point me in the right direction?

 

[Jacmar]

I'm no 1942 expert by any stretch, but just had a quick look at the schematics and personally I'd start on page 13 checking signals on the 2x 2114 sprite ram, the 2x LS157's at F9 and F10, the LS244 buffer at H7

 

[BubNotBob]

I'm no 1942 expert by any stretch, but just had a quick look at the schematics and personally I'd start on page 13 checking signals on the 2x 2114 sprite ram, the 2x LS157's at F9 and F10, the LS244 buffer at H7

That's the kind of info I need, I was concentrating on page 9 of the schematics as it said Scroll Position is that for the background tiles?

 

[BubNotBob]

Fixed!! Thank you Jacmar. I tested all chips as mentioned at F9, F10 and H7, all looked healthy but there is another LS244 buffer at H8 which tested duff so I desoldered it and popped in a new one and it's all working. It has been a bit of a journey on this one, as visually inspecting it I noticed lots of poor repair work done before, for example machined pin sockets that didn't hold the chips firmly this was causing the board to shift colours to yellow with any movement and other sockets that had no solder on the pins?? Obviously the previous owner ran out of interest part way through trying to fix it. Anway after a few hours of fixing all the obvious stuff that was wrong and checking roms and ram I was left with the stuck sprite problem which I must admit had me studying schematics and scratching my head.