Just a couple more comments...
On Sunday 22 August 2004 10:04 am, Thomas P. Gootee wrote:
> > There are also several connections to the rear panel, usually with only
> > one or two wires, that I need to worry about. I am thinking of using
> > either one- and two-wire pin headers and sockets, for those, or small
> > terminal blocks of some type. However, I still would LIKE to have all
> > pre-assembled cables (i.e. sockets already on both ends of
> > appropriate-length cabling.
> For something like that I've seen some commercial gear that used different
> styles of connectors (all 2-pin) so you couldn't mix them up and plug
> something into the wrong place. You could also handle that issue by
> setting the wire length to be only appropriate for where it's supposed to
> go and similar tricks. Something to worry about, anyway.
>
> === Another very good idea. Noted!
This would also probably involve making a "harness" for the wiring, which may
make things a bit more labor-intensive, and may also prove to be a
disadvantage when it comes to bundling stuff together that really shouldn't
be. I can't speak more to that without knowing more about what sort of
signals are running around in that equipment...
<...>
> The Osborne 1 computer had a weird custom board on their floppy drives,
> which was A and which was B was determined only by where the terminator
> position. This was before twists in cables and similar nonsense. They also
> ran the power for those drives up through the ribbon cable, to a card-edge
> connector. There were reliability problems with those over time...
>
> === Is it possible that the newer card-edge connectors are better, now?
No doubt they are, at least once things progressed beyond ISA slots. I have
heard of some ISA connectors giving trouble, and even encountered that
∗once∗ that I can recall (one of my XT-class MBs has a bit of black tape over
one slot :-), but have never heard of this being the case with PCI and AGP
slots, which use a different style of connector and a lot more pins.
<...>
> > If I were building something I think I'd probably tend to favor pin
> > connectors for signals and something a little heavier for handling any
> > kind of power, maybe a "pin connector" that's larger (0.156 spacing?) and
> > that uses the square pins for a better contact.
> Sounds right. I might even use the PC disk-drive-type power cables, for the
> heavier stuff. (I just missed a chance to get a lot of something like 500
> brand new "Y"/splitter PC disk-drive power supply cables, on ebay, that went
> for something like $10, total...! Those could have connected all three of
> the boards... :-o )
Now ∗those∗ have had their share of problems too. Like the common Molex
connectors, reliability leaves something to be desired when you're looking
at a female contact which consists of a bit of sheet metal that's going
around a pin, I don't know if this is a matter of what material is used for
the contact or not. There have been a few instances where I've had to take a
small tool of some sort and close them up a bit, after they'd opened up
some...
The same is going to be true to some extent for DB-xx connectors, though
they're better at it as the positioning and size of the male pins seems to be
more tightly controlled.
My preference for high reliability is contacts that have a "wiping" action,
which can be seen in the "Centronics" style connectors used on the back of a
printer, which I've also seen in sizes of 24 and 50 pins and there are
probably others. Some "external" connections on SCSI cards seem to offer a
miniature version of this, like on my Adaptec 2940uw, and the SCSI-wide
connector is similar in a 68-pin version as well. Some of the pin connectors
I've seen/used over the years are based on a similar idea, though I don't
have part numbers handy. The one half is a square pin (though sometimes
round ones are used too), and the other half is a bit of sheet metal that's
"folded" several times (think of an "@" character :-) and has some continuous
spring pressure holding it up against the other half. This is in sharp
contrast to a bit of sheet metal that's supposed to wrap itself around a pin.