Date   : Sat, 21 Apr 2012 19:06:36 +0200
From   : rick@... (Rick Murray)
Subject: Video Problems

Hi,

Just an off-the-top-of-my-head guess, but since the machine is responding
to video control and giving a valid video signal with a visible cursor, only
nothing is displayed...
...I would be inclined to check around the logic that handles the screen 
address generation. It would seem to me that there's nothing to display as
there is nothing being offered for display; though I'd equally have expected
to see "junk"? Is the input to the CRTC (or is it the Video ULA?) buffered?


Best wishes,

Rick.

Matt Walker <walker_matt@...> wrote:

>Can anyone shed any light on this weird fault.
>On turning on the BBC, it makes the first tone, but not the second. It 
>displays a mode 7 cursor where you'd expect it to be (after BBC Computer, 
>Acorn DFS, BASIC).
>Typing has no effect. After pressing BREAK (or CTRL-BREAK) however, if you 
>type, the cursor will move along, as it usually does.
>It seems to respond to commands, e.g. CLS moves the cursor to the top left. 
>The fault is not a teletext fault, as it happens in all modes.
>It's like the computer is working fine, but none of the characters are 
>there. Also, typing something like DRAW 1000,1000 doesn't change the screen 
>at all.
>
>The only thing I've tried is swapping the Video ULA, which has no effect at 
>all.
>
>Thanks in advance for all your help guys! 
>
>
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