Date   : Sun, 02 Feb 2014 23:51:55 +0000
From   : public@... (Daniel Beardsmore)
Subject: Problems with BBC Micro

What issue is it?

Early issues (at least up to 4) used a Ferranti ULA for the video controller 
chip, and they got hot and committed acts of permanent self-harm. The chip 
never burnt out, but you'd see all sorts of weird artefacts that would be 
consistently present forever. My first Beeb would draw yellow as red in 
MODE 2 unless you remapped the palette, and whichever mode Codename: Droid
ran in (1?), would show stripy colours under certain palette assignments.
It was like this for the three years I owned it.

The Ferranti video ULA was the only chip with a heatsink, and the video chip
is located just behind the OS ROM.

If this chip says "VTi" on it and it has no heatsink, it's the replacement ROM.

You *can* put the newer VTi chip in there -- I've done this a couple of times,
but it may break MODE 7 output under UHF (that's what I saw when I tried
it on one computer; in the other instance, I was using a monitor).


Just a guess, but it's one common cause of weird video issues.



On 2014-02-02 23:17, Chris Osborn wrote:
> Trying to figure out what might be wrong with my BBC Micro. When I go into
Mode 0 and hit return a bunch, the screen freaks out and does this:
> 
> http://i.imgur.com/qxrNCRQ.jpg
> 
> The computer doesn't crash, I can still type and switch modes and things. 
I found a type-in BASIC program that did a simple RAM test, and it didn't
find anything wrong. I don't have any other BBC Micros available to me, so
it's hard to try swapping parts around to narrow it down.
> 
> Has anyone seen anything like this before and might know how to fix it?
> 
> 
> _______________________________________________
> bbc-micro mailing list
> bbc-micro@...
> http://lists.cloud9.co.uk/mailman/listinfo/bbc-micro
>