Using EPROMs in place of NES Mask ROMS: 27CXXX series EPROMs, 27C64, 27C128, 27C256, 27C512, 27C010, 27C020, 27C040 NROM (mapper 0): No modifications nessesary CNROM (mapper 3): No modifications nessesary UNROM (mapper 2): Bend up pins 1, 2, 24 and 31 Solder pin 2 to hole 22 (A16) Solder pin 24 to GND (OE) SNROM (mapper 1): Bend up pins 1, 2, 24, 30 and 31 (or cut tracks 2, 24 and 30) Solder pin 2 to hole 24 (A16) Solder pin 24 to GND (OE) Solder pin 30 to hole 1 (A17) SNROM -> SVROM Conversion (mapper 1): Bend up pins 1, 2, 24, 30, and 31 (or cut tracks 2, 24, 30 and 31) Solder pin 2 to hole 24 (A16) Solder pin 24 to GND (OE) Solder pin 30 to hole 1 Cut track from MMC1 pin 11 to WRAM pin 20 Solder pin 31 to pin 11 of MMC1 chip (A18) Solder pin 20 of WRAM to Ground (CE (E1) or CHR /A13) SLROM (mapper 1): PRG socket: Bend up pins 1, 2, 24, 30 and 31 (or cut tracks) Solder pin 2 to hole 24 (A16) Solder pin 24 to GND (OE) Solder pin 30 to hole 1 (A17) CHR socket: Bend up pins 1, 2, 22, 24, 30 and 31 (or cut tracks) Solder pin 2 to hole 24 (A16) Solder pin 22 to hole 31 (CE or CHR /A13) Solder pin 24 to hole 2 (OE or CHR /RD) TKROM & TSROM (mapper 4): PRG socket: Bend up pins 1, 2, 24, 30 and 31 (or cut tracks 2, 24, 30 and 31) Solder pin 2 to hole 24 (A16) Solder pin 24 to GND (OE) Solder pin 30 to hole 1 (A17) Solder pin 31 to hole 2 (A18) CHR socket: Bend up pins 1, 2, 22, 24, 30, 31 (or cut tracks 2, 22, 24 and 30) Solder pin 2 to hole 24 (A16) Solder pin 22 to hole 31 (CE or CHR /A13) Solder pin 24 to hole 2 (OE or CHR /RD) Solder pin 30 to hole 1 (A17) TKROM -> TNROM conversion (mapper 4): PRG socket: Bend up pins 1, 2, 24, 30 and 31 (or cut tracks 2, 24, 30 and 31) Solder pin 2 to hole 24 (A16) Solder pin 24 to GND (OE) Solder pin 30 to hole 1 (A17) Solder pin 31 to hole 2 (A18) CHR RAM conversion: Seat the RAM chip 2 pins back (pin 1 of RAM is pin 3 of socket) cut track to hole 3, 22, 24, 28 and 29 Solder pin 1 to hole 30 (+5V) Solder pin 20 to hole 31 (CE or CHR /A13) Solder pin 22 to hole 2 (OE or CHR /RD) Solder pin 26 to hole 28 (+5V or RESET) Solder pin 27 to NES pin 56 (CHR /WR), you will probably need to glue in the missing tab on the PC board that goes into the NES, I used a thin piece of metal and super glued it, then sanded it with fine sand paper UNROM -> AOROM conversion (mapper 7): Bend up pins 1, 2, 24, 30 and 31 remove '32 chip cut track to pin 6 of '161 Solder pin 2 to pin 13 of '161 (A16) Solder pin 18 to pin 6 of '161 (D4) Solder pin 24 to GND (OE) Solder pin 30 to pin 12 or '161 (A17) Bridge gap between pins 10 and 11 where '32 was (A14) Bridge gap between pins 3 and 13 where '32 was (A15) remove solder gap for either V or H Solder NES pin 22 (CIRAM A10) to pin 11 of '161 drk421@yahoo.com