Date   : Wed, 07 Nov 2007 23:30:50 +0000
From   : zeem.uk@... (Alex Taylor)
Subject: Manufacturing fault

I stayed late at work today, getting carried away fixing one of the
Beebs I'd got from Wales some time ago. Previously I'd replaced the
cut off mains cable which revealed a dead PSU, then got someone else
to fix it (the BU208 transistor was faulty). Further testing revealed
a scrolling fault in modes 0, 1 and 2 which I fixed by swapping out
IC39.

It had been an Econet workstation without a disc interface, so this
evening I set about desoldering and swapping over the disc logic chips
from a dead issue 7 board with annoyingly soldered-in chips, and using
an 8271 from another machine (I'm one short because of a dead one I
had, although I may have a spare lurking somewhere). All I could get
when it was all fitted was the startup banner up to the "Acorn DFS"
text, and a continuous tone. I spent ages swapping chips around and
cleaning pins and sockets, and had almost given up, when I suddenly
spotted ... one of the pins for the 8271's socket doesn't go into the
hole in the PCB. It's bent out at a right angle underneath the socket.

I thought that it was funny that it's taken until 2007 - 24 years -
for a machine made in 1983 to have such a glaring production error
found. Only because it's spent its working life as an Econet machine,
and then many years stored in damp farm buildings - I'm guessing that
it was taken out of service because of the screen addressing fault.

I may be looking for another 8271 if I can't find my spare!

-- 
Alex Taylor