The first step was to see if a 2600 could run off 5v directly, to avoid using larger voltage batteries and a 5v regulator. It worked, the only issue was a color shift. It turns out the TIA color_ref pin wants about 4.2v and this is what that color pot adjusts. The next step was to see if the three ICs could fit into a dreamcast controller, which they did, but there was no room to replace the 6507 with a cmos 65C02 which would have dropped the power consumption even more. As shown in the photo below, the 6507 just fits between the two support posts of the controller.
As mentioned, the regulator was left out to save space. There was also no modulator needed (thank God) because lcd TVs have a composite input jack. One 100uf electrolytic capacitor was used for decoupling, and each of the three IC's has a 10uf hidding underneath them in the socket cavity. Most of the resistors and small caps used were surface mount ones "borrowed" from work. After gathering components, there was nothing to do but wire them all up, which was brutal. One trick which helped involved rolling a wire with an exacto knife to cut the insulation but not the metal. It took some practice but eventually I could open two parts of a wire and then strip the two ends so one wire could connect a four device bus (6507, 6532, TIA, cart-connector). A couple of my coworkers even said the schematic would be too much to handwire, they should have spent less time criticizing and more time guarding the surface mounts :)
Finally one night in the lab, the dreaded moment came to turn on power and see if anything would happen. This was stressful because there are limits to what a hobbyist can fix and it might have had some problem impossible to debug: noise, bus skew, race conditions. Flipped the switch and there was a garbled black and white playfield on the screen, but it was great to have that much working. Fixed the video mod transistor and got a solid black and white signal even though it should have been color.
It was then two days before CGE 2001, and there was no way to
finish it by then. However I did show people the rough unit and got
a lot of encouragement which helped.
next
