Date   : Wed, 01 Nov 2006 11:34:57 -0600
From   : julesrichardsonuk@... (Jules Richardson)
Subject: nutso keyboard decoding

Whilst talking about sick beebs...

Has anyone ever come across a beeb fault where keyboard decoding was 
completely messed up? Witchy over at Binary Dinosaurs has one (a model B) 
where the key which appears on screen hardly ever matches the key actually 
pressed, which is something of an odd fault!

We had another healthy beeb nearby (but no manuals or other tools) so tried 
the obvious 'quick fixes' - swapped keyboards, swapped ROMs (OS and BASIC), 
swapped 6522 chips, swapped CPUs, checked for obvious 'hot RAM', reseated 
anything that was socketed, checked under the PCB for invading metallic debris 
etc. but with no luck.

This was a couple of months ago, but I'm pretty sure I forgot to post about it 
to the list :-) Unfortunately it also means my memory isn't perfectly sharp - 
but recollection is that:

   Usually a few displayed letters would match what was actually pressed, but 
most keys produced incorrect results.

   The keyboard generally seemed a little 'sluggish' in response.

   Results varied between power cycles and weren't always consistent.

Is that a fault that anyone's come across before? Other than a Master that I 
have which transposes X, C and V I've not seen or heard of anything like it 
before. The fact that it otherwise boots up OK at least seems to indicate that 
memory and address decoding is reasonably happy. It's almost as though 
something was screwing up the data bus, but if that was the case I'm surprised 
the machine would ever get to a prompt...

cheers

Jules

-- 
If you've ever wondered how you get triangles from a cow
You need buttermilk and cheese, and an equilateral chainsaw