[Coco] Multipak redesign/replacement / New CoCo...

[Gene Heskett]

On Tuesday 24 February 2015 00:57:48 RETRO Innovations wrote:
> On 2/23/2015 11:42 PM, Gene Heskett wrote:
> > 40 wire ribbon is supplied in 25 or 50 foot+ spools, and the connectors
> > are all IDC.  The header pins soldered into the board are not that
> > expensive, although I would opt for the gold flashed versions of both the
> > header and the cable socket to improve the long term connectivity.
>
> Understood, but for signal integrity at the speeds we're talking, the
> crosstalk on the cable is what kills this.  We need cable that is:
>
> GND
> signal
> GND
> signal
> ...
>
> This is why many IDC flat cable assemblies have all of one side of the
> 2x pin header mapped to ground.  So, that's the "shielding" we need.

The 80 wire cable with 3 40 pin headers on it that I just checked, appears to 
have 34  usable connections in it, there are 6 of the pins on the side with 
the blocked pin tied together.  I wonder if there are true, 80 pin IDC 
connectors available for that stuff.

Ahh, no clue about the sheckles, but see pages 8 thru 14 or 15 of the pdf 
available at www.te.com.

These are very fine pitched on the board.  1/2 the pin spacing of the 40 pin 
IDC As for soldering there is a 4 row variant where they are staggered, which 
may help the soldering.  Available in up to 100 pin counts, the 80 pin 
variety would give us the full 40 usable signals. And the shielding we'll 
need.  And since in the stock MPI, the buffering logic runs on the coco's 
power supply, we could also use several strands for the +5 volt feed from the 
coco.  If well bypassed on both ends, the shielding effect of the alternate 
wire scheme will not be lost.

> As I noted earlier, ATA 6 IDE cables were the first thing I considered,
> but they only have 31 IO lines available, and we need 36 at the very least.

So the 34 I just measured isn't enough.  Raw cable and straight thru 
connectors.  If we can find 80 pin IDC's...  And I just did.  But it will 
take a query sent to their site to find a source and price. I don't recall 
seeing the TE brand on Digi-keys site, but could have missed it.  I expect 
others are also supplying similar products.  Thats is the first one I hit 
also and it was not in the first  3 google promotes.


> Jim
>
> --
> RETRO Innovations, Contemporary Gear for Classic Systems
> www.go4retro.com
> store.go4retro.com

Cheers, Gene Heskett
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