Old rubber HV wire

Discussion in 'Ham Radio Discussions' started by NM7G, Nov 7, 2020.

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  1. NM7G

    NM7G Ham Member QRZ Page

    I'm parting out a 3 kV power supply built 40 years ago. It was stored, unpowered in a dry basement for 35 years. Had no doubt the fat 450V electrolytics were heading for recycling, but didn't expect the condition of the high voltage wire. It was a major brand, bought from Allied Electronics by the spool. My gut told me it would be cracked, stiff and maybe brittle. Wrong! It flexes fine, the #18 stranded conductor looks good, and not a sign of cracking. The outside diameter is 0.230" +/-. Is this normal for rubber insulation of that era?
    KA4DPO likes this.
  2. WZ7U

    WZ7U Ham Member QRZ Page

    My first inclination is yes, for a certain application.
    I'm as surprised as to its condition though, must be something about minimal uv exposure.
    KA4DPO, NL7W and K4AGO like this.
  3. W9BRD

    W9BRD Ham Member QRZ Page

    It also has to do with rubber that's properly processed not to harden or get gooey and weird. Even just exposure to air kills bad rubber in time. Just leave a pile of rubber bands on a shelf for a few months and then try to zap a fly with one. It'll surface-crack as you draw it, and then probably break and hit you in the nose before you can shoot. (Not that I have experience with blowing flies to bits this way, mind you...)

    Oh, yes, and also be non-comical, proper rubber that acts like rubber. A few years back we bought a can of Chinese tennis balls at a local CVS -- the requisite fuzzy bright green. (I mean, isn't that the first criterion for a tennis ball?) Trouble was they'd thud on impact and bounce to less than half the drop height; it was like we'd bought them at a "jokes and novelties" store. I've seen checks bounce higher.
    N2EY, WA1GXC and N5PAR like this.
  4. WA9SVD

    WA9SVD Ham Member QRZ Page

    Sadly,I've gotten such tennis balls (and handballs) with similar complaints, made in other locations. It's poor (or prolonged) storage that takes the bounce out; even the "best' brands can (and do) have failures. Then again, sometimes you simply "get what you pay for (or usually less.)"
    N2EY likes this.
  5. KD8DEY

    KD8DEY Ham Member QRZ Page

    Green Balls??......
    I'm pretty sure the balls on my walker were always yellow,..
    (I'm not a tennis nut, So,,,,)
    Last edited: Nov 7, 2020
  6. KA4DPO

    KA4DPO Platinum Subscriber Platinum Subscriber QRZ Page

    The old high silicone rubber insulation was very, very high quality. It was not expensive because so much was manufactured at the time for use in TV sets.
    N2EY and KA0HCP like this.
  7. KA0HCP

    KA0HCP XML Subscriber QRZ Page

    I would consider 40 year old (1970's) wire and electronics components to be 'modern" in material type. The wire is without a doubt covered in synthetic 'rubber" and not the natural latex rubber that would have been found in 1950's and earlier wire.

    BTW, around 1961 the US electrical manufacturing standards changed disallowing the use of cloth covered wire.
    N2EY and KP4SX like this.
  8. KK4NSF

    KK4NSF Ham Member QRZ Page

    just curious: what standards are you referring to? Maybe consumer electronics? I'm asking because I know phone systems in some areas continued to use cloth covered wire in a few areas later than that. Not long ago a friend of mine gave me several spools of cotton covered phone wire that was tossed by the phone company, and it has mid-1960's dates on it.

    By the way, I'd like to find a few pounds of 36ga DCC wire for a project I'm working on.... but unfortunately, it's rather hard to come by here in the US.
    KA4DPO likes this.
  9. KA0HCP

    KA0HCP XML Subscriber QRZ Page

    I'm sorry, I don't have the reference available offhand. I've working from memory, and I don't feel like researching it tonight. I can remember that I had Motorola VHF FM commercial radios from 1960 and 1963 (20 tube types with 6146 finals). The earlier radio had cloth covered wire and the later did not. regards, bill. [edit: Perhaps the standard I recall is from the RMI, Radio Manufacturers Association.]

    Three years ago, I went to buy small diameter DCC wire for a project (coils and such) and was unable to find any suitable on eBay. This was the opposite of my experience from the late 2000's when I first became interested in Boat Anchors and homebrewing breadboard radios. I had no trouble finding DCC wire. I have not looked in the last two years, since my move.
    Last edited: Nov 8, 2020
    KK4NSF likes this.
  10. KA9JLM

    KA9JLM Ham Member QRZ Page

    Some of that silicone anode wire was very good.

    Not sure where the term "Boob Tube" came from, Maybe it had something to do with silicone enhanced wire. :)
    KA4DPO likes this.

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