Date   : Mon, 16 Apr 2012 20:53:14 +0100 (WET-DST)
From   : BBCMICRO@... (Peter Coghlan)
Subject: MODE 7 video corruption

>
>also i have just noticed that the keyboard input has gone weird again. some
>keys result in the wrong characters.
>

You didn't mention this before. This is a much trickier problem to solve.

Are the characters consistently incorrect or randomly incorrect? Can you list
some of the characters you are typing along with the incorrect characters
being produced so we can see if there is a pattern? Is incorrect characters
the only other problem or does the machine hang or otherwise behave
erratically as well? Does it work ok other than in MODE 7?

>
>This was the original reason why i swapped the user and system VIA's and it
>solved the keyboard problem but only temporarily it seems.
>This means i cant enter any of the BASIC commands/programs you have posted.
>

The problem might be intermittent or temperature related. The machine may
return to some sort of functionality for a while if you turn it off and let it
cool for a time. However, when a fault goes away temporarily, it is more
difficult to find what is causing it so you can't win...

Regards,
Peter Coghlan.