13 May
2015
13 May
'15
10:24 a.m.
I have a very strong suspicion that the answer to this is going to be 'no',
but I figured I'd do due diligence and ask...
I have a backplane (one of the rodent barn group) which has a couple of finger
contacts in the backplane missing. (Two came out while I was cleaning it - and
I wasn't being hard on them, they must have been eaten away by the same kind
of chemical action that lifted traces off the boards.)
Is there any way to replace broken/missing finger contacts? I would _guess_
'no', since it looks like the backplane blocks (the things cast out of dark
green plastic, which looks like Bakelite - anyone know exactly what it is,
BTW?) are cast around them (since there's a wire-wrap pin on one side, and a
finger contact on the other).
If the answer _is_ 'no', no biggie - all except one are on one SPC slot, and
it's a 9-slot backplane, so we'd lose one SPC slot - not the end of the world.
The other pin is in the UNIBUS in/out area (1/9AB), _but_ the antique hardware
gods are smiling on us, it's a ground pin (of which the UNIBUS connector
pinout has multiple, so we can probably withstand the loss of one).
Thanks in advance for any help!
Noel
13 May
13 May
1:16 p.m.
On 2015-May-13, at 7:24 AM, Noel Chiappa wrote:
I have a very strong suspicion that the answer to this
is going to be 'no',
but I figured I'd do due diligence and ask...
I have a backplane (one of the rodent barn group) which has a couple of finger
contacts in the backplane missing. (Two came out while I was cleaning it - and
I wasn't being hard on them, they must have been eaten away by the same kind
of chemical action that lifted traces off the boards.)
Is there any way to replace broken/missing finger contacts? I would _guess_
'no', since it looks like the backplane blocks (the things cast out of dark
green plastic, which looks like Bakelite - anyone know exactly what it is,
BTW?) are cast around them (since there's a wire-wrap pin on one side, and a
finger contact on the other).
If the answer _is_ 'no', no biggie - all except one are on one SPC slot, and
it's a 9-slot backplane, so we'd lose one SPC slot - not the end of the world.
The other pin is in the UNIBUS in/out area (1/9AB), _but_ the antique hardware
gods are smiling on us, it's a ground pin (of which the UNIBUS connector
pinout has multiple, so we can probably withstand the loss of one).
I don't know about DEC backplane connectors specifically - haven't dealt with them
closely enough for those purposes, but speaking generally:
To my recollection, of the wide variety of edge connectors that I've seen, 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. It can be a pressed dimple in the pin, a
slight crimp, or a twist. I'm looking at a wire-wrap edge connector right now in which
the pins were twisted 90 degrees after being inserted into the housing, right where the
pin comes through the housing. It can be quite subtle and one might need a magnifying
glass to recognise what's going on. It is sometimes possible to do a reasonable job of
replacing a pin (been there).
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. In the type of connector I'm looking at, if the pin broke at the
'right' place, it would be possible to pull one half out from the plug-in board
side and pull the remainder out through the backplane PCB, and then insert a good pin from
the plug-in board side, but I can't speak for whether that would be possible in the
case of a DEC edge connector.
2:58 p.m.
On Wed, May 13, 2015 at 1:16 PM, Brent Hilpert <hilpert at cs.ubc.ca> wrote:
As Noel posted, these are cast blocks of plastic with embedded pins.
They are not like the solderable edge connectors you are accustomed to
where the body is formed then pins are inserted. These are solid
blocks of thermo-setting plastic (i.e., it doesn't melt under new
heat, it chars and burns). There are no tabs, no "catches", no way to
release a pin.
-ethan
Is there any
way to replace broken/missing finger contacts? I would _guess_
'no', since it looks like the backplane blocks (the things cast out of dark
green plastic, which looks like Bakelite - anyone know exactly what it is,
BTW?) are cast around them (since there's a wire-wrap pin on one side, and a
finger contact on the other).
I don't know about DEC backplane connectors specifically - haven't dealt with
them closely enough for those purposes, but speaking generally: 
10:03 p.m.
On 05/13/2015 09:24 AM, Noel Chiappa wrote:
I have a very strong suspicion that the answer to this
is going to be 'no',
but I figured I'd do due diligence and ask...
I have a backplane (one of the rodent barn group) which has a couple of finger
contacts in the backplane missing. (Two came out while I was cleaning it - and
I wasn't being hard on them, they must have been eaten away by the same kind
of chemical action that lifted traces off the boards.)
Is there any way to replace broken/missing finger contacts?
On some of the
connectors, the pins are pressed in from the
card side. So, if you unsoldered or unwrapped the pin side,
you could, in theory, press the remains of the old contact
out and press in a new contact pin. i sold a box of 50
unused Winchester double-wide DEC connectors on eBay some
years ago. No idea where they are now.
Jon
3439
days inactive
3440
days old
3 comments
4 participants
participants (4)
-
elson＠pico-systems.com -
ethan.dicks＠gmail.com -
hilpert＠cs.ubc.ca -
jnc＠mercury.lcs.mit.edu