Date   : Wed, 20 Dec 2006 13:02:49 -0000 (GMT)
From   : splodge@... (Richard Gellman)
Subject: Curse of the long TUBE cable

> On 20/12/2006 09:03, Richard Gellman wrote:
>
> My memory could be failing here but I seem to recall there being
> something odd about the polarity of that cable (like it not being
> obvious which side is pin 1 at each end).  Are you sure you haven't got
> it crossed over?  Or if there's a transition header on the 6502 end,
> have the tines failed to make a good contact with the new ribbon cable?

I was very careful about that. I made sure the new cable was correct at
both ends, and only changed one end at a time. I've also checked both IDC
connectors for alignment and they are perfectly positioned.

> I have a Z80 2nd Processor board piggy-backed (daisy-chain fashion) on a
> 6502 and the extra cable length has never been a problem, so I doubt if
> it's the length that's the problem providing it's still reasonably short
> (300-400mm).

Mine is uh... about a metre *g*. My desk arrangement is somewhat
convoluted...

> The solution I used for my Z80/6502 combo was to power them from the
> Tube interface.  You'll find there are some links on the 2nd Processor
> boards to enable that, and if I recall correctly there are places to fit
> Molex shunts to provide those links.  I wired a centre-off two-way
> switch so that I could power up the Z80, the 6502, or neither.

I've heard of this... While it would be a reasonable solution, it would:

a) render the cheese wedge redudant and thus lose some of that show-off
quality :)
b) involve a switch either dangling free or mounted on the model B.
c) raise questions about the capability of the model B power supply, which
is already running a floppy disc drive and an Econet upgrade.

But I've kept this idea handy in case it happens to be the last resort.
Alternatively, I may rewire the cheese wedge to act simply as an
auxilliary power supply for the internally-mounted CPU board.

-- Richard