According to this diagram http://members.optusnet.com.au/eviltim/gamescart/gamecube.png there is a fourth cap on composite video line. Here is a low quality picture to see that are four caps: http://scorp.circuit-board.de/bilder/snes/rgb/auf1.jpg Does anyone know what is the purpose of that fourth cap on the composite video line (pin 9 to pin 20 SCART)? Thanks!
RGB and Sync, in this case Composite+C-Sync thats what the caps are for, all 220uf 16v if you'd look closer on the diagram, you'd have seen the fourth cap
That's correct DraggonC but for other consoles that cap doesn't exist. For example PlayStation 2 http://members.optusnet.com.au/eviltim/gamescart/psx.png So, that's why I've asked what's the purpose of that cap on composite video line. By the way, the GameCube PAL doesn't support C-SYNC "on the fly". You must use a sync stripper. Luma on sync RGB cable doesn't work because the PAL console doesn't support S-Video output.
The short ansawre It's basically because Nintendo have not been very consistent in the way they have implemented the outputs. There are variations not only between the 3 systems that used that cable (SNES, N64 and GC) and PAL/NTSC but even between hardware revisions of the same system in the same territory. The result of this is that some of these consoles have a DC-coupled video output with a voltage offset on it. Normally, this doesn't matter, since video inputs are typically AC coupled and have a clamp/level restore circuit on them, However, this is not always the case with the video input on the SCART socket, and in some instances these are also DC coupled. The overall result of this is that some combinations of console and TV won't work if you connect the signal straight through - although the same cable might work with a different TV or with a different revision of console on the same TV. Putting a capacitor in series with the signal will allow the case where both ends are DC coupled and the offset voltages are different to work without causing any adverse effects in other cases. The reason that they don't have a cap in the PlayStation SCART cable is that every version of the console that Sony ever made has AC coupled video outputs anyway, so it's unnecessary to supply an external DC block.
It's interesting because I have an RGB cable (it's "gold" plated) for the GameCube PAL made by Gamester and doesn't have that fourth cap on the composite video line... Instead it have some resistors on the ground pins. The caps for R G B lines are the correct ones 220uF. With or without that cap on the composite video line I don't know if will be some changes in the image quality but for the moment the cable is working good. That's why I was thinking that fourth cap was put there only to eliminate interference like a filter or something Here is a picture of the cable I have: https://images2.okr.ro/serve/auctio...6caed511dccd14cd78d9ff82cc-142533-700_700.jpg It is very sturdy
