pete at dunnington.plus.com
Sat Nov 8 17:04:19 CST 2014
On 08/11/2014 21:22, Jon Elson wrote:
> On 11/08/2014 12:26 PM, Pete Turnbull wrote:
>> On 08/11/2014 15:58, Noel Chiappa wrote:
>>> So it turns out that loose wire-wrap pins seem to be a systemic
>>> problem on 11/23's.
>> I wonder if it's exacerbated by the wire-wrapping being done.
> 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.
I didn't think Noel was referring to backplane pins - they're not
wirewrap pins nor do they carry the master clock - but to the various
jumper pins on the 11/23 PCB itself. There's a pair there to disconnect
the master clock for factory testing. Noel?
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