Why are there capacitors in some RGB Scart leads?

[Geezer]

I recieved a 3rd party Dreamcast RGB lead today, plugged it in and got an image that was heavily blue-tinted. A few quick measurements with a multimeter and for some reason the pin for blue colour was at a higher voltage than red and green. A couple of minutes with a soldering iron and 3 capacitors in the bin and I got a beautiful image which leads me to the question, why are they there in the first place?

Someone with some tech info must have the answer!

Geezer

[Papercut]

Its normally to do with smoothing/capping voltage peaks. Scart RGB signals should be something like 0.8v peak to peak, but some consoles push higher than that.

ntsc SNES' and pal Cubes also have capacitors in the scart cable, but without them the RGB signal strength is way to strong and you get an image thats far too bright.

[Geezer]

Thanks for the reply mate, kinda makes sense now!
A bit weird that they bothered putting them in the DC one though!!

[shortround]

ntsc SNES' and pal Cubes also have capacitors in the scart cable, but without them the RGB signal strength is way to strong and you get an image thats far too bright.

are you sure? i always thought capacitors were the things that increased the voltage and resistors decreased it. although i'm only going on hazy memories from CDT lessons at school. you've got me reet confused now.

[Abhisara]

From my limited understanding, NTSC SNESs output R, G and B signals with a dc offset, so you would need a capacitor on each line to filter out this offset making it compatible with the RGB SCART standard (otherwise the voltage is too high and the picture looks very bright). The RGB output signals on a PAL SNES don't have this dc offset, so the capacitors are not needed.

Not really sure about the capacitors on the DC lead though. Maybe they serve the same purpose. My (third party) DC RGB cable also has the 3 capacitors and works fine. Just guessing here, but maybe the problem was that the capacitor on the blue line had failed and hence you were getting a stronger blue signal than green or red.