Date   : Thu, 22 Feb 2007 17:38:45 -0000 (GMT)
From   : splodge@... (Richard Gellman)
Subject: BBC Problem

Hi,

> "As soon as the beeb is powered up the BBC Basic 32k information
> continuously scrolls vertically through the tv screen.  It moves upwards
> from the start off position and off the top of the tv screen.  It then
> appears at the bottom of the tv screen and moves to the top of the screen
> and then dissappears.  This process repeats itself continuously making it
> impossible to use"

Thats a loss of vertical sync. Check the VS line from the CRTC is making
it to the video hardware (part of the composite video mixer, and thence
the chroma circuit).

If the connection is intact, then it would indicate a faulty CRTC chip.

The former is easiest to test by trying the alternate video connections
(Composite and RGB), though if the fault persists it could still indicate
a break further back in the VS link.

-- Richard