Date   : Mon, 24 Aug 2009 22:31:18 +0100
From   : beeb@... (Kris Adcock)
Subject: Video circuitry repair

Evening all!

My issue 7 model B has a flickering composite video output. It flickers 
between about 5 and 20 times a second. It'll do this for a minute or 
two, then go stable, then resume again.

The flicker seems to be at its brightest at the top of the picture, and 
recedes away by about a third of the way down the screen.

I'd like to say that this only happens on the composite video output; 
however, the only RGB-input screen at my disposal is a 32-inch Samsung 
LCD TV, so I suspect that any flickering that may occur will be masked 
by the Samsung's video-capture and buffering circuitry.

I think it may very well be the case that it is specific to the 
composite video circuitry, though. Something about the extra bits of 
timing and porch signals that get added to a composite video output. If 
this is the case: does anyone have any experience of which components I 
should have a go at replacing? There is quite a dense collection around 
the composite video connector. One of the transistors or capacitors?

As an aside: I can heartily recommend plugging your Beeb into a big 
Samsung LCD TV via the RGB input. It's rock solid; Chuckie Egg looks 
AWESOME.

Many thanks in advance,

Kris.