Probably something wrong with those, i will meter them out with the logic tester later on.įunny thing is, the board tests these rams at boot. There's a pair of MSM2018 16K srams which relate to video, as far as i can tell from the schematics. One ram has pin 21 not grounded, all the other 64K srams do have this one connected to ground.
I scooted around the board with my multimeter, powered off, checking RAM. Note: Schematics show this is pin compatible with a 27C400 if anyone else needs to replace one at some point. The maskrom doesn't offer an explanation to the 'constant' jailbars i'm seeing. So, for now, the maskrom is not my real suspect anymore, i'm looking at other things. (Both these bars are around the 8th pixel on the screen.) Both are always visible, the second one scrolls right to left when walking. The first type of jailbar is white, and always visible, there's a second jailbar in the background area, which is yellow.
Tested the board a bit more & played a game.
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