Date   : Sat, 28 Feb 2004 21:40:01 GMT
From   : Pete Turnbull <pete@...>
Subject: Re: Sick Z80 Second Processor

On Feb 28, 10:56, Steve Inglis wrote:

>     I have a sickly second processor and I believe that I have track
this
> down to the tube cable. I've went an bought an IDE cable and it seems
to
> fit. I'm now trying to fit the IDE cable to the second processor
board and
> the bayonet type connects aren't taking.  My first instinct is that
pushing
> harder is probably a bad thing.

Yes, it probably is :-)

I'm slightly puzzled that you wrote "fit the IDE cable to the second
processor board".  All the normal second-processor boards have the
ribbon cable attached to a transition connector which is soldered to
the second processor printed circit board.  The cable is not removable
from the second processor end.  Only the BBC end of the cable has a
header to plug into a connector.  If your cable is completely
removable, it's most likely that someone has modified the second
processor board.

Assuming what you mean is that you can push the female header at one
end of the cable into a PCB-mounted connector with male pins, there are
a couple of possibilities.

One is that female ribbon cable headers come in two types: with, and
without, strain relief.  Original Acorn male headers on the BBC had
long latches (I expect that's what you mean by "bayonet type connects")
designed for the type of header with strain relief, which are bigger
than the type without.  However, many upgrades had short latches, which
only latch onto headers without strain relief; if you're referring to a
replacement header on the Z80 (where the transition connector would
usually be) it's quite possible that it has short latches.  If you have
short latches and your cable has a strain relief, the connector will
almost certainly make proper contact but the latches won't click into
place.  You can cure this by removing the strain relief if you want to.

Another possibility is that your IDE cable has 39 holes instead of 40.
 Quite a lot are made that way; the missing hole (near the middle) is a
key.  Unfortunately that means it won't connect to a standard 40-way
connector without damaging it, and even if it did, you'd be missing a
vital signal connection.

-- 
Pete                                           Peter Turnbull
                                               Network Manager
                                               University of York