Date   : Sat, 23 Feb 2002 15:48:49 +0000
From   : John Woodgate <jmw@...>
Subject: Re: BBC Micro repairs

I read in !bbc-micro that John Woodgate <jmw@...> wrote (in
<c5zCIHAubLd8Ewx9@...>) about '[BBC-Micro] BBC Micro
repairs', on Thu, 21 Feb 2002:
>Well, I'll check. I suppose the switches could have built up oxide on
>the contacts, too.

Progress! While checking the drive box, I remembered that the chap at
Technomatic had to build the box while I waited, and inadvertently put
the IDC connectors on the ribbon cable backwards. Now I've turned the
ribbon cable end-for-end, so that the more misleading connector is
hidden inside the drive box.

The result is that the Beeb with the Watford DFS and the drives now
work, BUT the discs with the critical information on were made with the
Acorn 1770 DFS, which is in the other Beeb and that one doesn't work.
The discs may be  Acorn 1770 DFS or IBM360K format, which is what I
bought the 1770 mod and DISCopy for. With the working Beeb, they give
the 'Sector not found' error message.

I am reluctant to swap the 1770 DFS into the working Beeb, because it
has a Watford ROM expansion board, which is physically incompatible with
the 1770 board.

The non-working board has the +5 V supply at all three feed points on
the board, but there is no tone on switch-on and no LEDs light. The
'cassette motor' LED lights momentarily when I switch the Beeb off.

I am an electronics engineer and I have lots of test equipment, but I
don't 'do' computers, so I'm a bit in the dark in trying to diagnose the
fault. I have the Beeb circuit diagram. I suppose I should look at the
power-up reset first, around IC16.
-- 
Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk 
Interested in professional sound reinforcement and distribution? Then go to 
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