I'm working on a P-47 that has faulty sprites. the graphics are missing.
I found this video which shows a RAM test function in P-47, but is it in the original ROM?
The test modes on these games are funny and inconsistent, i think you gotta hold start or something when the board is booting as well as the dip switch.
I have a 'test rom' for the 1c and 1b hardware that gives clear ram errors.
It's more work to port to the 1a system (p47) but will have a look sometime as got 2 faulty p47's here that looking at.
A pic of the fault may give some clues, seen B+C hardware do all kinds craziness.
Sprites go down post 6.
On my board there's some toshiba 6116 and a bunch of 157's close to the post, i'd check them first.
After those check the custom, post connections, 6264 rams etc.
This is assuming you have tested with a known good rom board.
I got this board today and trying to figure how to enter in the test menu to see if everything is working (the game seems to run fine from the attract mode). I've tried some combos at startup but only holding the service button I get the squares pattern but nothing else. Am I missin something?
The p1 button 2 was always pressed due to a broken JK-03, I've bought and installed 3 repros from @caius and now I'm able to pass the screen by pressing p1 button 1 and run all the tests!