Date   : Mon, 27 Nov 2006 23:17:05 -0000
From   : dl.harper@... (David Harper)
Subject: Master Keyboard t/shooting

"bbc" wrote:


> Hi all - Got my hands on my first BBC Master (shipped from the UK to Aus). 
> However, seems like the keyboard is DOA.
>
> The I, J, N, U and M keys are not working at all (and I suspect one of the 
> F keys is dead as well).
>
> I've stripped the keys off, air-brushed the dust-bunnies out, and hosed 
> the whole keyboard and switches with good quality contact cleaner. This 
> got a few sticky keys working properly, but not the 5/6 non-reactive ones.
>
> Seeing this grouping is too close to be coincidence, could this mean a 
> dead line/track on the board? Any suggestions on how to locate it 
> (preferably easy suggestions :-)

The keyboard matrix is published on p. 40 of the "Advanced Reference Manual 
for the BBC Master", available online at 
http://bbc.nvg.org/doc/MasterAdvancedRefManual.zip. This shows that the keys 
you mention, along with f6 and the 8 key, are all on line C5. According to 
the circuit diagram this should connect to pin 14 of IC16 on the main 
circuit board, via pin 15 of the keyboard connector. This connection must be 
broken somewhere. If you can identify it, then you could try bridging it.

Best of luck!

David Harper