Official GC RGB Scart Switching to Incorrect AV Channel with US SNES *Resolved*

[egparadigm]

Hey peeps,

I've got an official GameCube RGB Scart cable hooked up to my USA SNES. Works perfect, except for one, minor point: it switches to AV2 (compo****e) instead of RGB AV1, resulting in a scrolling screen of messed up colour.

Now, this is not a major problem, as I mostly only use AV1 on my TV and I can just leave it tuned to that. But, in the interests of learning more about how the thing works, can anyone tell me if there is a way of fixing this?

I use an MegaDrive 1 RGB cable which I wired up myself along with a host of other RGB cables without this issue (AFAIR). Looking inside the cable, I see that there is a purple wire going into contact 8, which I understand controls the channel switching.

Any ideas? Thank you!

[Hohum]

My USA SNES can't autoswitch my TV at all using RGB SCART, as the voltage or current supplied is too weedy. I have to switch it over manually every time. Might be the same problem you're having, albeit with a different effect on your tv.

[honeymustard]

Mine works fine.

It sounds like it's a problem as described here: http://mmmonkey.co.uk/console/other/rgbswitch.htm

Very easy to fix.

Edit: just took mine apart to have a look, and it's wired up correctly, so that's probably the problem for you two.

[egparadigm]

I actually contacted hellbelly before opening the thread. Anyway, let's press on.

Found this thread earlier, in which I found some suitable pictures. The below is how my one is wired up. There is a separate circuit board which is out of shot, here:

http://nfggames.com/forum2/index.php?topic=3203.0

Anyone able to tell me if re-wiring is the correct measure, here?

Also, any idea how to unsolder these, as the connections are quite deep inside these pins - not sure how to get to them?

[Hohum]

Mine works fine.

It sounds like it's a problem as described here: http://mmmonkey.co.uk/console/other/rgbswitch.htm

Very easy to fix.

Edit: just took mine apart to have a look, and it's wired up correctly, so that's probably the problem for you two.

Hmm... I've tried three cables over a period of time, and they all did the same thing (GAME branded cable, Gamester professional cable, and Nintendo's official cable). None of them would allow my tv to autoswitch when using the SNES, yet all of them worked fine connected to a Gamecube. I'm not disputing what you're saying as it could well be that very issue, but what are the odds that all three cables are wired incorrectly? Are all the companies involved that incompetent?

@monomaniacpat: I think in your case you can just push the pins through from the other side (they're held in place by little ridges on either side of the pin, so a small screwdriver should do the trick).

[Link83]

I have experienced this exact same problem with both an NTSC SNES and a NTSC N64, and eventually found out what the problem was and 'kind of' solved it.

Bascially the Scart standard requires 9.5-12v on Pin 8 and 1-3v on Pin 16 to 'auto switch' to the AV1/RGB channel in a 4:3 aspect ratio. You can read more about it here:-

http://en.wikipedia.org/wiki/Scart#Blanking_and_switching

Now on a PAL SNES and a PAL Gamecube (not the PAL N64) Pin 3 of the 'Nintendo Multi AV out socket' is the 12v line, and Pin 10 is 5v (which goes through a 100ohm resistor to bring it down to around 3v for the Scart standard)

On an NTSC SNES (and NTSC N64) Pin 10 is still 5v, BUT Pin 3 is Composite Sync! (Or C-Sync as it is sometimes called) Not 12v.

Now there is no easy way around this on a SNES as there is no 12v power internally, so what you can do is make the 5v line power both Pin 8 and Pin 16 (Through a 100ohm resistor) on the Scart cable - this should make you TV switch to the AV1/RGB channel correctly - the only side effect of this (as you can tell from the above wikipedia link) is that 5v on pin 8 will usually switch you TV to 'Widescreen' mode (if it has one) but if this doesnt bother you read on...

To do this on an Official Gamecube cable please look at the following picture I have made of the Official Scart cables circuit board (The colours I used on my picture should match the colours of the actual wires used in the cable, and are not related to the type of signal its carrying. You can tell this because the RGB wires in the Official cable are not actually coloured Red, Green and Blue):-


All you need to do is place a blob of solder between the +5v line and the '+12v' line -marked in Red and Blue on the picture. Make sure you put your blob before the 100ohm resistor - so basically you need to join together the bottom two left red and blue points shown on the picture.

Then cut the red +12v wire after it comes out of the cable, but before it enters the circuit board. If you dont do this the +5v that we have just redirected can end up travelling back down the cable, into your SNES, along the C-Sync line, and then end up overpowering the poor little SNES's Video Chip - we dont want that! (I did the same thing on an NTSC N64 and destroyed the video chip by sending +5v into it) So please make sure you cut this +12v wire if you join the points. Also it is probably wise to put some insulation tape over the wires cut end - just as a precaution.

Please remember, once you have done this modification the cable will only ever switch to AV1/RGB 'Widescreen' mode even if you then use it on a PAL SNES/Gamecube (Unless your using a 4:3 TV that doesnt support Widescreen modes of course!)

Phew! Hope that helps !

<EDIT> Hold up, thats a picture of my Gamecube Scart cable and a link to my thread at nfgforums!

<EDIT 2> Thought id better add that the Official Gamecube Scart Cable is not the easiest of Scart cables to open, so I made a picture showing how to open it which you may find useful (The text is abit small but if you save the picture and zoom in you can read it)

[egparadigm]

<EDIT> Hold up, thats a picture of my Gamecube Scart cable and a link to my thread at nfgforums!

Yes! I wondered if you'd come waltzing in here with your Sonic avatar and your knowledge of Nintendo scart cables.

I'm tempted to do as you say, but I'm very worried by the prospect of blowing up the SNES's video chip. Is that the only way to do it, or is there an alternative? Or is there a way to test before plugging in - perhaps I could run a continuity test with my multimeter?

[egparadigm]

Then cut the red +12v wire after it comes out of the cable, but before it enters the circuit board.

Reading this again, I think I misunderstood. You want me to cut the wire, not the link on the circuit board? So I cut the red wire going into the top-left solder point in the picture? That sounds a bit easier!

EDIT: looking at the scart here, I want to cut the red wire going into the bottom-left solder point, correct?

[egparadigm]

Done! And it works, too. Plus, my SNES hasn't blown up... yet.

Now I know a tiny bit more about scart cables.

It still works on my PAL GameCube, too, although presumably now it will auto-switch to 16:9 on a widescreen telly. I always wondered what controlled widescreen mode. I guess a Sky/terrestrial digi-box sends a different voltage down the cable when it wants to tell the TV it's a widescreen programme?

Thanks for your help.

[Link83]

Yes! I wondered if you'd come waltzing in here with your Sonic avatar and your knowledge of Nintendo scart cables.

Lol! im no expert, but have just been reading up on all the Nintendo AV cables over the last few months and think I have a much better understanding now of how they work.

Sorry I couldnt help you earlier - I have been out all day.

Reading this again, I think I misunderstood. You want me to cut the wire, not the link on the circuit board? So I cut the red wire going into the top-left solder point in the picture? That sounds a bit easier!

Yes cut the actual red wire, not the circuit board trace, sorry if I wasnt very clear.

EDIT: looking at the scart here, I want to cut the red wire going into the bottom-right solder point, correct?

That depends on which way round you are looking at the circuit board. If you are looking at it from the point of view shown in my picture you want to cut the red wire before it connects to the bottom left red point in the picture.

Dont cut the red wire between the circuit board and the Scart plug, only cut it between where it comes out of the cable, and before it goes into the little circuit board.

If it is switching ok and the SNES is working fine im sure you have done it right

For future reference I made a little picture showing just the +5v and +12v lines which hopefully makes it alittle clearer what this mod does:-

[egparadigm]

Yeah, I meant bottom-left, there! (Correct that for future look-ups.)

Also, I worked out what was going on...

[mmmonkey]

Link83, some fantastic info in this thread mate

monomaniacpat - glad you got it working, and glad I couldn't help in a way - otherwise Link83 prob wouldn't have posted!!

[Link83]

Link83, some fantastic info in this thread mate

monomaniacpat - glad you got it working, and glad I couldn't help in a way - otherwise Link83 prob wouldn't have posted!!

Thanks! but actually I have you to thank for the original idea

I was looking at your mod for AV/RGB switching and started wondering why/how it worked, and if there was a way for me to impliment it on an Official Gamecube scart cable, and after abit or studying I came up with this method

One slightly interesting thing I realised was that the third party cable that you used (From Play Asia) is actually missing the +12v wire entirely - its not even in the actual cable!

To compensate for this they joined Pin 8 and Pin 16 with a 100ohm resistor - basically the same as I did with this mod. The only problem is they actually connected the +5v wire to the wrong scart pin as you noticed.

With the way they wired it Pin 8 = 3v and Pin 16 = 5v which doesnt really match with the Scart spec at all. Some TV's 'might' switch with this arrangement, but most wont.

After you perform your mod Pin 8 = 5v and Pin 16 = 3v which is much closer to the Scart spec, and should make it switch to the AV1/RGB channel in Widescreen mode

Anyway, glad I helped someone