Why are there caps in the PAL GC RGB scart cable?

[Hojo_Norem]

Tonight I was prodding around in my Gamecube's RGB cable (which I bought from Game) in a attempt to reduce the interferance on the sound output.  Considering not to long ago I RGB modded a PAL Master system and I used a 6 pin din socket and made a RGB wired 6 pin din plug to scart cable, I thought that 'why not cut most of the offending cable off my GC rgb cable and witre a 6 pin socket on the end and have two phono cables for audio?'.  Then I realised, I did'nt put any caps in the din to scart cable.

So I decided to try my de-capped SNES rgb scart cable on my GC and the picture looked just the same as with my GC scart cable.

What do the caps actually do in the scart cable?  Ill it harm my GC if I remove them? (in the act of making my custom cable, as my Master System, Mega Drive and Dreamcast self built RGB cables all have no caps and work fine)


The 'high screen contrast' audio buzz I get sometimes can be quite bad.  Either reducing the amout of distance the audio is in the same cable as the video or building a digital audio out interface for the digital av out port seems to be the only answer.

[AntiPasta]

I have no idea where the caps are for. I opened up various Saturn SCART leads, the official one had a capacitor sitting between 2 pins whereas the 3rd party ones had none  :huh:

Moreover, this 'high contrast buzz' you speak about, do you mean a buzz coming out of the TV's speakers when lots of white or other bright colors are being displayed? I have that with my Dreamcast, very annoying. I wonder what causes it, as I'm using an official SCART lead and I cant imagine it's not shielded enough.

[Hojo_Norem]

Moreover, this 'high contrast buzz' you speak about, do you mean a buzz coming out of the TV's speakers when lots of white or other bright colors are being displayed? I have that with my Dreamcast, very annoying. I wonder what causes it, as I'm using an official SCART lead and I cant imagine it's not shielded enough.

Yeh. thats what I mean.  Its even worse on my de-capped pal snes scart lead.  I don't det in on my Dreamcast cable though, is I tap the audio right from the connector (eaisly done, the DC connector is effectivly a shell which can be opened to gain aggess to the wiring points for the various signals).

Does anybody know of any make od GC scart lead which taps the audio at the GC end rather the SCART end?

[davidleeroth]

Moreover, this 'high contrast buzz' you speak about, do you mean a buzz coming out of the TV's speakers when lots of white or other bright colors are being displayed? I have that with my Dreamcast, very annoying. I wonder what causes it, as I'm using an official SCART lead and I cant imagine it's not shielded enough.

You could try to connect the audio pins to ground via suitable resistor and see if that helps reduce the buzz.

 

[Hojo_Norem]

Got round to hacking my GC scart cable last night.  There was a immediate improvement in sound quality, I had to turn my amp up to near sucidal levels to hear the buzz on the Smash Bros. sound test screen.  And the added bonus was that I used the leftover cable to mae a longer din to scart cable! ^_^

[ozpass]

I'm guessing that the capacitors are there as "smoothing capacitors".

As the power supply comes from a rectified AC source at 50Hz, the DC current output by the RGB circuitry will consist of pulses at 100 Hz.  Without a smoothing capacitor, this would then produce interference.

Somewhat odd, however, that removing them has no discernible effect.  :blink:  

[Vertigo]

They have the same effect as hmmm ok let me explain.
If you have a PAL SNES you can use a straight-wired SCART lead with it, but if you try using this lead on a NTSC SNES, you end up where the picture's ok for a nano-second then just fades up and up to almost completely white.
This is what would happen on your GC if you didn't have the caps in the SCART.
OK?

[Hojo_Norem]

They have the same effect as hmmm ok let me explain.
If you have a PAL SNES you can use a straight-wired SCART lead with it, but if you try using this lead on a NTSC SNES, you end up where the picture's ok for a nano-second then just fades up and up to almost completely white.
This is what would happen on your GC if you didn't have the caps in the SCART.
OK?

Strange, my current, cap-less setup has a near spot on pitcure on my new / old PYE 25" tv.

<Ramble>

Got it for nowt, takes RGB (auto and 'forced') and 60Hz!  All it needed was a new backup battery cause it kept loosing its tuning....  Ah one of the vary few advantages for working at a indipendant electrical retailer,  if I take something new to a customer and they say 'Just get rid of it, oh it still works' then it either ends up as a second-hand set, a loan set for the repair shop or it just gets junked.  This is the first I have saved and if I find a better one, the PYEs goin in the paper at 30 quid!

</Ramble>

[Bikkuri!]

This might not relevant to the topic, however i bought a third party gamecube SCART cable. When i opened the housing, it does have three capacitors sitting in each of the RGB lines. But when i plugged the cable in, it just gave me black screen. I checked and i found that the video ground is using the audio ground. Instead of using different cable from the GC, it just tapped cable to the audio ground on the scart pin. Could this be the problem? I tried to find information about GC SCART cable on the net but no luck.

[Lawrence]

Ground is ground, it doesn't matter where it's connected as long as it IS.  Video ground is no different than audio ground.

That said, the proper value for the caps is 220uf, if your cable has off-spec caps (which is often the case for 3rd party gear) it may fail 'cause of that.  Also, make sure it's a SCART cable, not an RGB cable (euro pinout vs japanese)