Thoughts on using old mica capacitors

Discussion in 'Homebrew and Kit Projects' started by K8AI, Jun 5, 2017.

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  1. K8AI

    K8AI Subscriber QRZ Page

    Yep, we used ATC porcelain caps in our TCAS transmitters at my last job and they're used in the 6 GHz uw digital radios I maintain at my present job. They're a bit on the pricy side, I'd say. Some I've seen were around $30 each!
     
  2. K8AI

    K8AI Subscriber QRZ Page

    Thank you Dave, that's the kind of advice I was fishing for.

    I didn't want to do it but I think I'll end up digging into my precious stash of silver micas that I was hoping not to use.
     
  3. WA7PRC

    WA7PRC Ham Member QRZ Page

    Fortunately, to build a single unit, the cost is one-time. And, while quality isn't cheap, the labor cost of a failed unit is MUCH higher.
     
  4. KA9JLM

    KA9JLM Ham Member QRZ Page

    Sometimes a smoke test is the best for HV caps. :)

    Test 1 and you get a idea of what the rest in the batch will do.
     
    K8AI likes this.
  5. K8AI

    K8AI Subscriber QRZ Page

    Doesn't scare me one bit. I'm not producing commercial gear, I'm building homemade stuff that I, alone, take full responsibility in using. I think sometimes folks on QRZ forget that we're often not engineering commercial gear, just ugly, junk-box specials to be used by the builder, alone.
     
  6. WA7PRC

    WA7PRC Ham Member QRZ Page

    Too often, the most important (or only) criteria to hams is cost. They're "penny wise and pound foolish." Those folks make cheapskates look like big spenders. In this case, porcelain (or similar) caps make sense. And the greater cost hurts only once. :)
     
  7. RICHS

    RICHS QRZ Member

    I have silver mica and the bigger CM 45,55,60 transmitting mica and ceramic caps from the '60 and 70's that are still perfectly good. The old caps I would throw away are paper, electrolytic, and any other cap that is not sealed. Caps that are no longer manufactured any more I would throw away. The were replaced with newer designs for a reason. True mica dialectric caps last virtually forever.

    I use old caps that I have experience with and the one's I don't I may not throw them away but I wouldn't use them in a new project in a big quantity, Having to replace a large number of old caps that turned out bad would change a fun project into a nightmare.
     
    Last edited: Jun 8, 2017
  8. K8AI

    K8AI Subscriber QRZ Page

    What you call being a cheapskate and "penny wise and pound foolish" is sometimes just being reasonable and practical, you know, how hams used to be - it's just the way one looks at things.

    I'd say there's a place for NASA-grade redundancy, protection and quality but when YOU are the technician and in control and the one taking the risk...

    It's ham radio, for crying out loud, relax and enjoy yourself. :)
     
    N5DMC and N0TZU like this.
  9. WA7PRC

    WA7PRC Ham Member QRZ Page

    I do. :)
     
  10. WA9SVD

    WA9SVD Ham Member QRZ Page

    I thought everyone knows the alphabet starts with "F:rolleyes:"
     
    N6RGR likes this.

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