SCART -> TV without dedicated AV channel

[Hamselv]

Hi there,

I am collecting the equipment needed to build a MAME cabinet, and just encountered a small problem:

I got a 21" TV for free, which I will use until something better comes along. However, when hooking up my old ASUS 6800 card with a composite or S-vid to SCART converter (a common SCART plug with plugs for video and sound in the back and an Input/Output switch), I get no signal to the TV.

I think my problem might be that I have no dedicated AV channel on the (rather old) TV. I tried hooking it up to my VCR, which worked great both with SCART and through coaxial cable alone. The VCR will pass through the antenna signal by default and switch over as soon as I play a VHS tape, just like intended.

Why isn't this happening with my video card TV-out signal? Does the VCR send an extra signal through the SCART cable, ordering the TV to switch over when it should?

This is still a bit confusing to me, so I am hoping someone here can add a few of the missing pieces in my head

[teacup]

To get the tv to switch automatically there needs to be a current passed to one of the pins on the scart lead. I can't remember which pin so you'll have to search on google for some details. You have to think about how you want to get a current on to the pin, if you're making a cabinet you could just have a lone wire from your computer, anyway, thats all I can think of.

Oh and make 100% sure theres no proper av channel first, it would be a ---smurfette--- to go to all this trouble and then  someone comes round and says "oh, you just have to press this button..."  

[teacup]

I found this site:

http://utopia.knoware.nl/users/eprebel/SoundAndVision/Engineering/SCART.html

At the bottom it gives the details you want.

You need to put a voltage of 9.5 - 12 v on to pin 8 to get the tv to switch automatically.

[Hamselv]

Excellent!

That's just what I needed. A friend of mine has just hinted at something like this, but it is nice to get a firm reply.

I guess I can just grab a constant 12V from the PC power supply, then.

Just  to be sure: Do I apply one wire to pin 8 and the other to the shield?

Thanks