Update: I cannot get video to pass through the HVBUF pcb to the monitor. Video works fine without the HVBUF however. What could be causing this other than a bad PCB?
Nevermind, it turns out the HVBUF needs 5v to pin 1 on the 4 pin connector. There are three different versions of the game, two of them show that the 5v is supplied through the monitor cable coming from the naomi, the third shows the 5v being supplied by the power supply.
The game is playable and the guns shoot accurately in 15khz mode. However, the graphics are very poor. Needs a good comb filter to look decent because you can barely read the text.
Thanks for the update. I'll have to keep 31kHz capable monitor on the want list for a dedicated gun cab.
On another note, I'm curious do you happen to have any other Naomi lightgun games? I doubt they'd work since they normally use an IR rig, but it'd be fun to try.
As far as I know all the other Naomi gun games use the sega IR gun system which is very cost prohibitive. HOTD2 is BS compared to the original anyway. None of the IR gun games make my short list(except terminator salvation, got $8k to blow?). Carnevil, Area 51, original House of the Dead. Invasion is growing on me as well.