NTSC-Cartridge Conversion for PAL-Eproms
I've got a few 7800 NTSC games which won't play nice with my PAL 7800, so I've decided to change the NTSC-roms to PAL-versions of the same game. I've found the guide for the 32k ones and those worked fine, but now I've got a 48k pcb (One on One) where there are 2 mask roms on the PCB, a 32k and a 16k mask rom. How can I convert the pcb for either one 64k 27c512 eprom or two eproms (32k 27c256 + 16k 27c128)? This is the board in question C026445.
You'll find a schematic for your board here: http://www.atarihq.com/danb/7800cart/C026445.shtml The "Chip Enable" pins on both roms should be labeled "/CE" in that schematic, as they must be active LOW. Basically U1 (16k rom) is selected when A14 is HIGH and A15 is LOW, that is for addresses $4000 to $7FFF, while U2 (32k rom) is selected when A15 is HIGH ($8000-$FFFF). I would have used a single 64K eprom in U2 (you only need to isolate pins 1 and 22 by cutting traces on the board) and a NOR g
