SCART RGB Video

The SCART connectors found on most European TV sets provide an easy way to achieve high-quality video almost directly from an arcade board's video signals. If you don't have a SCART TV, this page won't be much use to you, but there are plenty of guides on the web which explain how to convert to component, composite or S-Video.

Looking at the JAMMA connector, we see pins for red, green and blue, a sync signal, and a dedicated video ground. As luck would have it, these map almost 1-to-1 to what we need to provide our SCART TV with (although the dedicated video ground isn't always necesary, often any old ground will do). In fact, it is possible to connect these pins directly to the SCART TV and you will most probably get a picture. The JAMMA video signals are however of a slightly higher voltage than SCART expects and whilst unlikely to cause any actual damage, the image is likely to be overly bright.

In order to tone down the signals, we add some resistance to the equation. Usually a fixed resistor of 75-100Ω on each of the red, green and blue lines is enough, but it's little extra effort to use variable resistors which will allow the separate components to be adjusted individually to obtain the best possible picture. I've seen values quoted for such variable resistors (a.k.a. potentiometers or "pots") between 250Ω and 10K, so anything between those two should at least work to some degree. I ended up using 1K pots as these were readily available in the size I required and with push-on knobs. In any case, you need the linear type of pots for this, so that the brightness changes in a regular fashion as you turn the knob.

The SCART connector also has pins for audio, which can be taken from the level converter as described [link: later]. Other connections of note are the +5V through a 220Ω resitor to pin 16 (selects RGB mode on the TV) and the +12V to pin 8 (allows the TV to detect our signal and automatically switch to our SCART socket for input).

Next: Audio >>