16 May
2015
16 May
'15
12:57 p.m.
the fingers are cast in place or least they are on the 8i backplane
i know this cause i have a bucket of smashed up bits from the 8i i found..
On Sat, May 16, 2015 at 6:48 AM, Noel Chiappa <jnc at mercury.lcs.mit.edu>
wrote:
> it looks
like the backplane blocks .. are cast around them
From: Brent Hilpert
all have secured the pin in the housing via some
deformation of the
metal
pin, post-insertion; as opposed to moulding the
housing around the
pin.
From: Ethan Dicks
these are cast blocks of plastic with embedded
pins.
From: Jon Elson
On some of the connectors, the pins are pressed
in from the card
side.
There appears to be some question as to whether thyy are cast in place,
or inserted.
Actually, I started to wonder about my assertion shortly after I posted it,
and took another look at the backplane. The thing is that the hollows that
the finger contact pins are in are fairly complicated (since they allow the
contact pins to move back and forth, but hold them from going too far), and
I'm really wondering if it would be possible to cast that shape, and then
remove the mold, and also have the pin in there. So I'm wondering if in
fact
they weren't inserted post-casting.
From: Brent Hilpert
The problem in your situation of course, is
getting the remainder of
the pin out from between the edge connector housing and the backplane
PCB without having to unsolder the entire connector.
Well, I'm kind of assuming they are inserted from the edge-connector side,
and not the wira-wrap pin side (what with the contact pins being bent, etc
on
the edge-connector side), If they _were_ inserted from the wire-wrap pin
side, I'm totally @&@^$#%@&^, there's no way to get that PCB off now.
So in theory, at least, I'd have to de-solder them from the PCB and then
try
and push the remaining part back through (after identifying and defeating
whatever the capture mechanism is - which I might not be able to reach with
the PCB in the way). And then I'd have to find replacement pins and put
them
in. Both of those sound non-trivial.
(All assuming, of course, that they are inserted post-casting, and not
cast into place... still not sure about that.)
This has assumed a little extra urgency as on closer examination, some of
the
pins in the UNIBUS in-out area are clearly very weak - I imagine there's
only
a tiny bit of metal holding the contact pin in place, and it could break
off
any time. And I won't be so lucky as to have them all be ground pins..
So if one breaks off, the backplane is toast (unless it's the the last
thing
on the UNIBUS, it could be kludged - i.e. attach the termination/ pull-up
directly to the wire-wrap pin).
Which I guess is not the end of the world - DD11's aren't _that_ rare...
Noel