I thought about making a way to bridge past the potentiometers if they are not desired in a specific setup. The idea with this board is to just install the components needed for a specific application. The pots may not be necessary on the PCE/TG16, but other applications may require them.
What other applications, exactly?
Off the top of my head, I can think of two consoles that need need a video driver circuit to get the RGB working sensibly. There's the PC Engine and the Nintendo 64. In both cases the amplitude of the signal at the point inside the console is 0.7Vpp. I doubt this is an accident. All you need is a standard (ie. gain of two) driver stage and you're done. No fiddling required. It is better to making something that serves its sole purpose well than some kind of one size fits all device that doesn't really fit anywhere.
The PC Engine's video signal is a little bit more tricky to work with due to the large DC offset, but a properly designed video driver will work on the N64 too with no modification required.
I consulted the guy who's been helping with the design of this chip concerning this issue. He said he selected this particular chip because it is self biased and doesn't require a coupling cap.
He's wrong. Read the datasheet.
In short, there are three possible biasing techniques that can deployed against this part.
1. DC coupling - connect the video signal straight into the chip. This works because there's some special 200mV (or thereabouts, I don't have time to check) internal reference which is added to the input. It prevents the signal from banging into the negative rail on the output (which would cause distortion). This method will work with the N64 RGB signal (those units with the signal available, that is) because it varies between 0v and 0.7v. The PC Engine's video video signal measures between 4.3v (black) and 5v. Hopefully you can see why direct coupling is not an option.
2. AC (Capacitive) coupling with sync tip clamp - This part has inside it what is known as a sync tip clamp. I did a quick search an found a circuit of this arrangement here:
Look for Figure 4 (a). This works just fine for a video signal with the sync signal poking through the bottom of it but will distort the bottom of the waveform if you try it on sync-less video (such as what you are dealing with). This is the way you currently have it configured - maybe - you didn't post a circuit diagram.
3. AC (Capacitive) coupling with resistor bias network - this one you want is what you want. Bias the input at about 1V DC or perhaps slightly less to allow maximum output swing without getting near the limits of the output stage or the nasty sync tip clamp. Your bias voltage will be much more critical if you go for the part with higher gain. You probably need capacitive coupling on the output too, otherwise you may exceed the power dissipation for this part when the loads are connected.
Anyway, the datasheet explains it well, read it thoroughly.
