hpglow wrote: The other being the AVR UC3 fpga (there is one in the series that will take 5.5V) mounted to an pdip adapter. The reason being these are the only two microcontrollers that run on 5V, and most modern controlers take 3.3V. While it is easy to put a regulator on the fpga to pidip adapter board the problem would actually be with the ladder DAC on the main board. All the resistor values would have to be different for 3.3V. I suppose a complete pcb "shield" of some kind could be plugged into the current board but that would up the cost.
Mounting chips to a PDIP adapter would be an idea. Most arcade machine upgrades and expansions tend to involve removing the CPU from the motherboard, inserting the CPU into the socket on the expansion board, and then putting the expansion board in the CPU slot on the motherboard. Applies with other chips as well.
As for the resistor DAC. For example, take the three red output resistors. Tie all three inputs together, the resistance is about 456-457 ohms. That's not too bad. So a possible solution would be tying all inputs together and put a DAC with less resistance behind the resistors on the Uzebox board. But at the same time once this board is complete there's not too much left to add to make it a complete system.
I think software would be a good approach first, maybe some original games (Working on one for the Uzebox JAMMA, very difficult).