Re: WTD: Transwarp GS ribbon cable. Improvements?

["Michael J. Mahon" <mjmahon@aol.com>]

RichardK-PB wrote:

<snip>

> Also - it occurs to me that modern technology could help make Transwarp 
> ownership less fraught. Specifically, the screen-printed dual-layer 
> ribbons that they use in modern laptops and the like. More flexible than 
> the ribbon cable, lighter, could be made much smaller, and the molex end 
> could have one of those pull straps on making it easier to remove. I 
> know people make these in relatively low runs - the Apple Newton 
> community gets small ones made up for eMates to cure a common problem.

The problem is not so much the cable (ribbon cable is actually more
reliable than printed cable), but the IDC DIP plug's connection to
the ribbon cable.

A properly designed and staked IDC connection is hermetic, but an
improperly designed one, or one designed for a different type or
size of wire, will not be hermetic, and so is prone to degradation
over time.

A further issue is strain relief, since too much strain near the
connection will also damage hermeticity.  Some IDC connectors
incorporate a 180-degree bend of the cable at the connector to
reduce strain on the actual connections in use, but DIP plugs
seldom do.  In such a case, an external 180-degree bend (or two)
could be introduced and fastened with, say, silicone adhesive
(if there is sufficient vertical clearance, which is questionable
in this application).

> Not sure how to cure the DIL header, but I know that parts exist for 
> this which could be higher quality than the AE provided components - 
> round, gold-plated pins for example. I've seen these used on BBC 
> computer upgrades.

Again, the problem is not so much with the connector pins as with
the IDC connections.

However, a further issue is the compatibility of the DIP plug with
the main board socket.  Many DIP plugs have thicker pins than IC's,
resulting in good connections in a socket previously occupied by
an IC, but in poor connections if an IC is subsequently replaced
in the socket, because of inelastic socket "spreading".

IC sockets, in general, are a two-edged sword.  They are very
handy for experimenters (compared to soldered-in chips), but
they are also notoriously unreliable (non-hermetic) as a result
of temperature variations ("creep") which leads to oxidation.

Even gold-plated contacts are only reliable for between a few
and a few dozen insertions, since the abrasion of the contact
surface creates tiny furrows through the thin gold plating,
inviting oxidation.  Abrasive cleaning accelerates this problem.

-michael

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Home page:  http://members.aol.com/MJMahon/