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Plugged my Pi into our old TV for the first time yesterday, using composite, it worked ok for a while, then flickered into black/white.

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Fiddling round with the cables, I discovered that just holding the Pi in my fingers was enough to get it to display in colour again. I think (my fingers are too fat to be sure) that just 'shorting' the whatever-it-is labelled C74 seems to do the trick.

Any ideas what this could be? Or should I be hacking config.txt to force into a different mode?

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This is weird. Definitely sounds like a hardware thing. I'll have a chat with some guys at robotics. –  Jivings Dec 30 '12 at 14:23
    
B&W output on composite sometimes means that the signal from the computer is too high. Don't know if there are easy/cheap ways of attenuating it a little. –  scruss Dec 30 '12 at 14:48

2 Answers 2

You could try testing some other sdtv values in the config.txt file.

Try adding the following line to the /boot/config.txt file

sdtv_mode=2

Try other values: 0 is NTSC, 1 is Japanese NTSC, 2 is PAL, 3 is Brazilian PAL.

I'm not 100% sure that this will actually work, considering you said that it used to work and now doesn't. But hey it's worth a shot.

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If the TV is expecting a PAL signal, if it receives NTSC it will be in black and white. You could try to switch the TV into NTSC and see if that helps (NTSC cannot display PAL at all, so that rules it out). Otherwise as the previous answer said, try changing the output mode. If that doesn't work, it may be a hardware fault.

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