DC Picture problem

[babs]

I've recently moved rooms at home, and the consoles have gone with me. I've just hooked the DC up via the RGB cable I have for it and thru an RGB scart switcher.

When I turn it on I get sound but no picture, just a black screen. The TV swtiches to the AV channel and shows that it's getting an RGB signal, there's just no picture. When I hook it up via composite RCA plugs on the front of the TV then it's fine (actually a very good pic for composite).

I just wondered if there's a known situation or problem that could result in this?

[Saurian]

Different TV?

The reason you are getting a blank screen is due to the display not switching to RGB mode, the DC does not output a composite video signal when an RGB cable is plugged in (composite sync instead) hence the blank screen when RGB mode is not on. Check your splitter to make sure the RGB button is on.

If you are using a splitter can you leave another machine plugged which works OK through RGB plugged in and switched on? This way you can force the mode.

[babs]

There is no RGB button, the switch is fully RGB wired. When the DC's input is selected on the box, when I power it up it is getting the sginal and automatically turns to AV1, and the display tells me it's switched in RGB mode.

The cable is an odd one I suppose, it seems to be sending an RGB signal to the TV, but near the DC end of the cable there's a small block to take RCA plugs out, which work fine.

[Tom Salter]

I had this problem on my mum's TV, the telly definately supported RGB but my Dreamcast wouldn't display a signal, no matter what I did. I just didn't see my mum for the whole time the Dreamcast was 'popular'

[Saurian]

Have you got a multimeter?

Open the SCART connector and check what value resistor you have between pin 8 and 16, should be 75ohms. Have a go at what I suggested earlier, if you have another machine which will display correctly on this TV with an RGB cable, have it plugged into another socket on your splitter and switched on.

[babs]

I don't have a multimeter :/

I've tried the other device in RGB on the splitter and powered on and it doesn't work.

[Hitcher]

If, after turning on your DC and leaving it on, you can plug in the composite cables and get a picture then either the cable isn't RGB or the switcher isn't.

[babs]

The switch definitely is, I've tested all ports with a working source. I can only assume it's a composite cable which for some reason is telling the TV it's RGB, as it's telling me it's getting an RGB signal. That would fall in line with the composite box on the same cable and mismatched sync frequencies I suppose.

[Saurian]

It's saying it's an RGB cable most likely because pin16 is supplied with voltage in it's SCART connector.

The TV is not detecting an RGB signal - the voltage on pin16 determines whether the mode is activated or not. As Hitcher says if you can get a composite signal out of that cable's output via phono cables plugged in it's not an RGB cable at all (the Dreamcast will not output a composite video signal if an RGB cable is plugged in, it switches over to composite sync instead)