32X Restore SMS Support

A Sega 16 thread went over the process on how to restore Sega Master System support to a 32X.

"I finally got around to finding the chip and wiring it up... everything works as expected. Here's a (beautiful M$ Paint) diagram and some pics of how I did the mod. 32X_pbc.jpg

The idea is that you need to allow A21-A23 act normally in Genesis and 32X mode, but drive A21-A23 in SMS mode. So this circuit controls the direction using /M3 (pin B30) to pass the 32X signals when high, and pass the PBC signals when low.

• Start with a 74ACT241 (pin 1 is at the top of that picture), and bend/solder/cut the legs to jumper the necessary connections. DSC02684.JPG
• Solder to A21-A23 (pins B9-B11) on the edge. Use a piece of tape to prevent the solder from flowing down the edge pin (which will wear out the system socket). DSC02685.JPG
• Cut the traces to separate the 32X output from the cart socket (don't mind the solder on the traces... that was from re-connecting it during testing). DSC02687.JPG
• Find a place to put the chip (I attached it with double-sided tape under one of the white cables). DSC02689.JPG
• Solder wires to the 32X A21-A23 output (CN1 pins B11-B13), and +5V/GND (left side of capacitor is +5V, right side is GND). DSC02691.JPG DSC02692.JPG DSC02693.JPG DSC02694.JPG
• Route the wires where they won't get in the way of reassembly, solder to the chip according to the diagram, reinstall white cable. DSC02695.JPG DSC02696.JPG DSC02697.JPG
• Test DSC02698.JPG "