Date   : Sun, 05 Feb 2006 01:16:52 GMT
From   : Pete Turnbull <pete@...>
Subject: Re: Making a 3.5" Beeb floppy drive

On Feb 2 2006, 12:49, Chris Thornley wrote:

> The drive select jumpers are hardwired by jumpers to DS1 this can be
found
> and removed and DS0 jumpered if required.
>
> If you wish to use a cable with a twist instructions about how the
cable
> work are here :-
>
> http://www.hardwarebook.net/cable/storage/floppy.html

No.  Not relevant, and won't work for a Beeb.  It does work for an
IBM-compatible PC, which uses a different method of addressing the
drives than a Beeb.  You presumably missed the somewhat lengthy
discussion about this a few weeks ago.

> The power connector details are as follows
> http://www.hardwarebook.net/connector/pc/smallpower.html

That page doesn't tell you what the connector actually is; it's an AMP
EI (Economy Interconnect) 4-way with a 2.5mm pitch (not 2.54mm or 0.1"
as many people seem to think).  The cable connector is AMP 171822-4,
female contacts are AMP 170204-1 (26-30 AWG) or AMP 170205-1 (20-26
AWG).

I (and several other people) have submitted additions like this, and
corrections, to that website but I've never seen any of them added.  Be
warned, it's a useful resource but there are quite a few errors and a
lot of assumptions in those pages.

> The BBC connector is a little hard to find these days you might be
best
> cannibalising an old one or
> Checking out http://rswww.com/ RS components to see if there are any
> suitable replacements.

There aren't, really.  The correct in-line connector is AMP 1-250234
with male pins AMP 350664-1.  No other connector type fits, though
Molex pins for their old 0.093" connectors will fit the female contacts
in the power supply.  The connector incidentally is the same as the
ones used by ASTEC for Apple power supplies.

> Finally you might require an 8 way keyboard jumper :-
> http://www.maplin.co.uk/Module.aspx?ModuleNo=2387&TabID=1&source=17&WorldID
> &doy=2m2
>
> These are required to configure the BBC to operate with higher pulse
> response drives and are fitted to the holes bottom right of the BBC
> keyboard.

You can use that to change the step rate of the floppies but it's not
actually *necessary* to do that.  It may make some drives quieter, and
it may effectively speed some things up slightly.

-- 
Pete                                           Peter Turnbull
                                               Network Manager
                                               University of York