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Thread: DIP Switch Story.

  1. #11

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    Quote Originally Posted by Dwight Elvey View Post
    Many switches used silicone grease. These always used a non-conductive filler. Over time the grease it self would evaporate, leaving the non-conductive filler.

    Dwight
    That is very interesting. The material left behind on these switches might well be that filler. If it is , it is very hard and it takes more than plastic passing over it to wipe it off. The problem with those CTS switches is that they were not meant to be pulled apart for cleaning and/or re-greasing. I wonder why they put the non-conductive filler into the grease, was it for thermal conductivity ?

    Invariably these switches are soldered to the PCB and for the sake of preserving a vintage computer pcb they should probably only be un-soldered once. This is why I have decided not to re-solder new DIP switches of a similar type in their place. Instead go for a high quality DIL socket with the more modern sealed compact DIP switches. The better ones it seems , like the Omron types, are in the range of $3 to $5 each (many others are about $1.50) but I'm not very keen on making a $ saving in this area, due to the diabolical problems and time consuming fault finding if a DIP switch is intermittent. As far as I see it, the replacement switches should be the best that money can buy, be sealed and have the sliding contact design.

    It is good that many computer manufacturers went to jumpers across pin pairs (rather than DIP switches) as these are easily cleaned and tend to stay clean with a bit of exercise and be reliable, mostly.
    Last edited by Hugo Holden; November 25th, 2018 at 09:12 PM.

  2. #12

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    The grease needs something added. Neither the oil or the filler is conductive, It works because silicone grease has almost no film strength. Even a slight force will allow metal to metal contact, even if it has to push the filler out of the way. Automotive dielectric grease is essentially the same. The grease is such a good non-conductor that it is often used for high voltage coaxial connectors. A friend did under sea stuff ( you know sensors for various things ). He'd fill the voids in the BNC connectors with silicone grease and then cover them with riggers tape. The grease gave better connection and kept the ocean out. I believe most of the stuff he did was less than 100 feet deep though.
    The grease does conduct a little though. I worked where we were using a mass spectrometer. It had a selector switch for the current ranges of the sensor ( you know precision gigiohm+ resistors ). I was having stability problems on some of the scales so I put some of the grease on the ceramic switch ( bad idea ). I spent the rest of the afternoon, cleaning the switch with solvents. It turned out that there was a tiny hairline scratch across a PC board's copper trace. On high humidity days it worked fine. On dry days it didn't. Since it was on the output side of the electrometer amp to the feedback resistors, it had tiny currents. I put a little solder across the scratch and all worked fine. SO I can say that it might conduct a tiny amount.
    Dwight

  3. #13
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    I believe that US "purple twister" wire nuts are filled with dielectric grease (used when joining aluminum to copper). Not my favorite situation, by any means. I've also seen telco splices filled with something resembling dielectric grease.

  4. #14
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    Quote Originally Posted by Chuck(G) View Post
    I believe that US "purple twister" wire nuts are filled with dielectric grease (used when joining aluminum to copper). Not my favorite situation, by any means. I've also seen telco splices filled with something resembling dielectric grease.
    The stuff for aluminum bonding isn't dielectric grease, at least not normal translucent silicone dielectric grease. I've got it in tubes for making setscrew style connections on larger aluminum cable, the stuff I have is black.

    Telco and automotive connector grease is usually the plain yellow/white silicone dielectric grease you can get at the auto parts store.

    DIP switch longevity problems aside, I still prefer them to a heap of jumpers!

  5. #15
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    My "purple twisters" have clear-to-translucent grease in them, so YMMV.

    My 3M telco splices have clear goop in them.

  6. #16

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    Quote Originally Posted by Chuck(G) View Post
    I believe that US "purple twister" wire nuts are filled with dielectric grease (used when joining aluminum to copper). Not my favorite situation, by any means. I've also seen telco splices filled with something resembling dielectric grease.
    I think you mean the UR-type splices. They're clear plastic with a round red IDC button. The goop in those is just some form of waterproofing - WECo had a zillion forms of that, from the thin "icky pic" all thr way through to the "bathtub caulk that never hardens" inside the network module in telephones. Oddly, UR-types were mostly used in interior work (they were an easy way to "bug" a 3rd wire, since they were 3-terminal connectors - cut the existing wire and put both ends in, then the added wire, then close. Most older outdoor stuff used non-waterproof (white) B-type ("chicklet") connectors, probably because the insulation on the wires being joined was often paper, so waterproofing the connector was the least of their problems.

  7. #17
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    I've got those with both green and red buttons. I recall when a wayward truck knocked over the telephone pedestal for our house, severing the wires. I grabbed a bunch of the UR splices and hooked the phone lines back up and then called repair service. "At least you used the right stuff" was the comment by the tech.

  8. #18

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    I replaced the DIP switches on three 16KRA memory cards and the DIP switches on the SOL-20 main board with the high quality Omron switches in machined pin IC sockets. It is a big improvement, now they are reliable.

    Pics attached.
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