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Oddball GEC Marconi military electronics
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coppice:

--- Quote from: Syntax Error on December 08, 2020, 06:12:15 pm ---I noticed in your image how neatly bound together the cables on the D-Plug are. Someone was meticulous with lacing chord! I understand, possibly from a Dave Youtube video, cable ties are a big no-no in avionics. Tthe edges of plastic ties can chafe the cable insulation through the mechanical vibrations of flight. Lacing chord is kind to cables. For an avionics manufacturer, doing things this way would be just another day on the assembly line.

--- End quote ---
That is not an especially good lacing job. Super neat lacing is a core skill for wiremen in defence work. The best wiremen can tie them faster than most people can apply cable ties, so there is no cost overhead in using them, and they take less space.
adriansmith31:
I tore down a interface unit LRU that was filled with cards plugged into a backplane which was entirely wire wrapped. The workmanship of it was fantastic. Was a shame to pull it apart. It's here if anyone is interested https://www.adrian-smith31.co.uk/blog/2020/09/panavia-tornado-avionics-lru-teardown/#more-934
coppice:

--- Quote from: adriansmith31 on December 08, 2020, 06:55:48 pm ---I tore down a interface unit LRU that was filled with cards plugged into a backplane which was entirely wire wrapped. The workmanship of it was fantastic. Was a shame to pull it apart. It's here if anyone is interested https://www.adrian-smith31.co.uk/blog/2020/09/panavia-tornado-avionics-lru-teardown/#more-934

--- End quote ---
I'm surprised that has a wire wrapped backplane. I'm also surprised by the edge connectors they used. Most things used DIN 41612 connectors at that time, and thick many layer backplanes were the norm for flight use. The rest of the construction is pretty standard. PCBs with a thick tinned copper heat ladder. The heat ladder then pressed against a cold wall. No air flow over the PCBs. These boards all have conformal coatings, but that was uncommon with cold wall cooling. Its absolutely essential if air can flow over the boards, as there can be a lot of salt corrosion when flying over the sea without it. I can't see the back of any of the boards, but I expect there is a teflon strip down the edges, so the card slides smoothly into its slot. That was banned later on, as teflon was removed from flight systems as a hazard in fires, and was only permitted where it was essential for its RF performance. Teflon doesn't burn, but if you get it hot enough in breaks down into fluorine compounds which are no fun on an aircraft in trouble. Those big 106 pin connectors on the back were used in many Avionics LRUs. There are a number of versions of the plastic shells in those connectors, offering options of thicker pins, coaxial feed-throughs and so on. The pins look a bit vulnerable at first sight, but they are very robust and reliable in practice. The ones in that box seem to be wire-wrapped. I'm used to crimped ones.
adriansmith31:
That thing dated from 1976 I believe and had at least one card replaced circa 1982. I don't remember seeing any teflon coatings but the boards slid in and out smoothly. Definitely no airflow over the boards and I imagine it would have got rather warm in there with the power supply module at the front.

I was very surprised myself to see wire wrapped connections in something that is subject to a lot of vibration, heat and cold stress.
coppercone2:
so did anyone figure out what RAD means ? maybe to draw a radius on the picture to measure a circle?
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