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Re: WTD: Transwarp GS ribbon cable. Improvements?

Michael J. Mahon wrote:


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.


*nods*
One hopes it was properly designed. However, what I notice is that whilst the Slot 3 position is recommended, in both ROM 01 and 03 models, this results in the ribbon cable being folded over or bent in other awkward ways. There is minimal clearance there.
With Slot 4 the standard cable lies flat and IMO would actually be better, but it's pulled over the top of the ROMs. I don't think this is very healthy either. 


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.
It could be that the IDC connector is failing. Either way, the solution is the same - new connector! 


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).
Definitely not, IMO. Hence, what I would envisage is the DIP socket, with a printed ribbon cable inside it. It could be much flatter and have a thicker than usual mylar/base, making it quite robust. 




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".


*nods*


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.
And there are a lot of problems like this on my Apple IIs now. The ][ Plus required extensive (cleaning to work). 


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.
With devices like the Transwarp, I tend to assume the idea is that once installed, it stays installed. The pins on the DIP plug were oxidised, as were the pins on the card's IDC header (extensive cleaning and a light abrasion seems to have helped a little, but the cable is still suspect). I mean, when I got the card it was dead and the IDC had green corrosion on it, so it's clearly been affected by this at some point.
The IIgs has been very flaky though, even without the VOC installed I have had some glitches from it today; RamFAST errors and the like. I can only assume the PSU is planning on making an exit soon. 

Richard

--
RichardK - 1980s in a can. http://www.dmc12.demon.co.uk/music/
Retro computing - http://www.dmc12.demon.co.uk/retrotech/
Cars - 2004 Beetle Cabrio, 1989 Supra 3.0i, 1990 Sera
MidiGuitar, Enterprise 128, AU/X. Apple 77-04. See links ;)