8 Nov
2014
8 Nov
'14
3:02 p.m.
On Sat, 8 Nov 2014, Jon Elson wrote:
On 11/08/2014 12:26 PM, Pete Turnbull wrote:
It would have been hand soldered. Wirewrap pins can't be wave soldered
since that would contaminate the gold or silver plated pins with solder
(the solder would dissolve and strips the gold or silver from the pin).
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. 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.