8 Nov
2014
8 Nov
'14
1:22 p.m.
On 11/08/2014 12:26 PM, Pete Turnbull wrote:
On 08/11/2014 15:58, Noel Chiappa wrote:
I'm guessing the problem was that the wire wrap pin had
broken free of the solder
joint to the etched PC board? My guess is more along the
lines of frequent
board insertion/extraction fatigued the solder joint, as
pushing the board in/out
does wiggle the pin just a little. I haven't seen this
problem either on DEC
stuff, but I can imagine it happening. it might have been a
batch of backplane
that was not soldered quite properly, either temp profile
wrong or some kind
of contamination of the solder bath.
Jon
So it turns out that loose wire-wrap pins seem to
be a
systemic problem on
11/23's. I just discovered _3_ more on one single 11/23
board - two of them
the pins for the master clock! I put my finger-tip on
them and wiggled, and
they were loose.
I've had dozens of those pass through my hands or at least
across my workbench and I don't recall ever seeing that.
But given your experience, it's clearly something to watch
for nowadays. I wonder if it's exacerbated by the
wire-wrapping being done.