Date   : Mon, 16 Feb 2009 14:56:58 +0000
From   : splodge@... (Richard Gellman)
Subject: Dead(ish) BBC B - Pleae Help

On Sun, 15 Feb 2009 21:24:15 -0000, "Mark Haysman"
<jumbos.bazzar@...> wrote:
> Hi.
> 
> Sounds like a classic case of a dead System VIA at IC3. Take the one out
if
> 
> IC69 and put it into IC3 spot, see if it cures it. Could be a bad socket,

> that system VIA controls the keyboard and the slow bus to the Sound chip.
> 
> Mark.
> 
> ----- Original Message --

Also consider the addressable latch. This selects which of the slow devices
is being written to/read from. If this is selecting multiple devices at
once or not selecting anything at all it would explain the tones and the
lack of keyboard response.

A 74LS259 chip IIRC. It'll be close to the System VIA.

-- Richard