This is the corrected schematic for the KAY256.LBR 256K ram modification for '83 series KayPro computers, Models II and IV. This one works fine! Also, you Turbo-Rom users may want to see the text file TURBO256.TXT. Many thanks to Dr. Liddle and to all those who debugged this fine mod! Charles McHan AMY <> BBS MULTI-SYSTEM (904)725-7461 \_TABLE I\_ Signal on Chip on Board Kaypro II/IV REFRESH U48 pin 12 MUX U33 pin 1 A14 U33 pin 11 A15 U33 pin 10 RA7 U20 pin 9 RA8 U20 pin 1 PIO 1 Pad E29 PIO 2 Pad E28 PIO 3 Pad E31 \_FIGURE 1\_ \l0i +-----------------------------+ | | | +--------+ | | +------| 7 |- 0v | | | -| 4 |----------+ | | -| L |- | | -| S |- | | 0v -| 3 |- +--|------| 9 |- 0v | +5v -| 3 1|----------o----------< RFRSH | +--------+ | | | 33R | +--------+ | RA7 <-- / /---|------| |- 0v | +------| 7 |- | +---------| 4 |- | | -| L |- | | -| S |- | | -| 1 |- | | 0v -| 5 |- 0v | | +5v -| 8 1|----------+ | +--------+ | | +--------+ +---------| |- 0v 33R A14b >------------o--| 7 |------------ / /--------> RA8 \_| 4 |-----------------o------< PIO 2 PIO 1 >---------------| L |-< +5v >-/\/\/\_/ 4.7k 0v -| S |-----------------o------< PIO 3 A15b >---------------| 1 |-< +5v >-/\/\/\_/ 4.7k 0v -| 5 |------------------------< MUX +5v -| 3 1|- 0v +--------+