For units with serial numbers 794801 and later
Remove 2708 EPROMs from IC sockets U102, U103, and U104
Remove 7442 decoder from IC socket U108
Cut -5V and +12V traces on top rear of CPU board as indicated
Power up unit
Verify no -5v present on U126 pin 21 and no +12v present on U126 19
Power off unit
Connect U108 pin 12 to U126 pin 20
Connect U108 pin 14 to U126 pin 21
Connect U108 pin 15 to U126 pin 19
Insert programmed 2732 EPROM into IC socket U126
Power up unit, test, and enjoy
2732 EPROM address mapping:
2708 ROM0 (U104) 0x0000-0x03ff -> 2732 0x0000-0x03ff
2708 ROM1 (U103) 0x0000-0x03ff -> 2732 0x0400-0x07ff
2708 ROM2 (U102) 0x0000-0x03ff -> 2732 0x0800-0x0bff
OBX rev IB for 2732 EPROM [BIN] - Checksum 000472AD
|
