Date   : Wed, 20 Dec 2006 17:46:51 +0000
From   : pete@... (Pete Turnbull)
Subject: Curse of the long TUBE cable

On 20/12/2006 13:02, Richard Gellman wrote:

>> My memory could be failing here but I seem to recall there being
>> something odd about the polarity of that cable

> I was very careful about that.

Fair enough.

>> 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...

Ah.  That's probably too long.

>> The solution I used for my Z80/6502 combo was to power them from the
>> Tube interface.

> 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 :)

You may be right -- there may not be enough room in the cheese wedge for 
two cards.  But if there is, you could still do this, just break the 
links between the 5V rail and the 5V Faston tab on each, and fit the 
switch there.

> b) involve a switch either dangling free or mounted on the model B.

Mine's mounted between the sandwich of the two processor boards, which 
are uncased.  If they were in one case, I'd just put it on the back.

> c) raise questions about the capability of the model B power supply, which
> is already running a floppy disc drive and an Econet upgrade.

It has a fair amount of spare capacity.  I used to have one Beeb with 
two floppies on the auxiliary connector, speech processor, a 
fully-populated ATPL ROM board, Econet, internal Econet clock and 
terminator, an EPROM programmer powered from the User Port, and the two 
2nd processors.

-- 

Pete                                           Peter Turnbull
                                               Network Manager
                                               University of York