Date   : Mon, 20 Jun 2005 16:47:55 +0100 (BST)
From   : Chris Johns <chris.johns@...>
Subject: Re: A couple of questions - Econet & 1770 Disc Interface

On Mon, 20 Jun 2005, Mike Howard wrote:

> I also have an Issue 7 BBC/B who's history I know little about (I
> believe it came from the Depatment Of Chemical Engineering at Nottingham
> University) and cannot get the disc interface to work. I'm using a known
> good floppy drive, known good disc interface, known good 7438s and the
> link is fitted at IC86. IC87 is fitted with a 74LS123 but unfortunately
> not socketed.

You need to modify the 1770 interface to fit it if one of the ICs is
present and not socketed. There is a pad on the corner of the interface,
the track between the two pins needs to be broken and one side soldered to
a pin on IC87.

I don't recall the exact details, they should be in the 1770 fitting
guide, I have a copy but its 200 miles away - I can find out when I'm next
home if required.

I had to do this when fitting a 1770 DFS interface to a machine that had
previously had a 8271 controller.

Cheers

Chris