Video DAC



The NeoGeo uses a discrete video Digital-to-Analog Converter made of resistors fed by two 74LS273 latches which store the color value from the palette RAM and 74LS05 inverters. This is controlled by either, or.





Note: The schematic has a typo and shows a 74LS06 instead of 74LS05 but both can be used.

Each color component has its own set of 7 resistors. 6 of them are used for the actual color value (5 + 1 common bit). The last (SHADOW signal) is related to the and  registers (system latch).

Arcade
The output isn't lowered like on the AES. It goes straight to the JAMMA edge as a 0~3.5V signal for the high-impedance inputs on arcade monitors.

Home
The output is divided by 2200 / (6800 + 2200) = 4.1 to obtain a ~0.9Vp-p max signal, which feeds the video encoder for amplification and conversion to composite.