Date   : Sun, 10 Apr 2005 21:29:52 +0100
From   : "John" <blip@...>
Subject: FW: BBC to VGA Video In/Out

So if I read you correctly gentlemen, it shouldn't matter how big or
cheap the TV is - it should still be clearly legible when using an RGB
to TV Scart lead on the BBC providing you limit the voltage?

Presumably I can take the scart plug apart and just solder on the required
Resistors - can't for the life of me remember the numbers though (you can
never forget the colours given the phrases!)

Black
Brown
Red
Orange
Yellow
Green
Blue
Violet
Grey
White is it...? Anyone care to remind me what the sequence should be for 150
ohms?

Do I need to dig out one of those horrible text diagrams of a scart plug to
work out which pins to damp down?

John 

> > I recently purchased an RGB cable for my BBC to connect to the 28"
TV.
>
> > Unfortunately the display is awful, very blurred, which I think is
down
> > to the size/quality of the TV.
>
> It sounds as though your tv is getting too much signal is your lead
fitted
> with dropper resistors.

I think Ian has the answer, especially since John put "VGA" in the
subject line.  A VGA monitor, or a TV with normal RGB, expects an
analogue signal at around 1V peak-to-peak; the Beeb output is TTL
level, which is about 4V peak-to-peak.  You want to throw away 2/3 to
3/4 of the voltage, and the easiest way is to use dropper resistors in
series with the red, green, and blue signals.  Since the input
impedance of a TV is nominally 75 ohms, resistors in the range 150 ohms
to 220 ohms ought to be about right.

-- 
Pete                                           Peter Turnbull
                                               Network Manager
                                               University of York