tubes getting gassy over long term storage

Discussion in 'Amateur Radio Amplifiers' started by KA5ROW, Oct 28, 2017.

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  1. KA5ROW

    KA5ROW XML Subscriber QRZ Page

    Since there is an issue of 3-500 and other type tubes getting gassy over long term storage. Why did they not put them in sealed cans with the same gas that was in the tubes. I am sure the cans would over time have oxygen invade them like the tube. but I think that would gave the tube a much longer tube life. Maybe adding at least 20 to 30 years.
     
  2. N8VIL

    N8VIL Ham Member QRZ Page

    There is not supposed to be any "gas" in a tube. Just a vacuum (absence of any gas) or as close to it. Over time air from the ambient atmosphere leaks past the seal between the pins and the glass. Possibly out gassing of the tubes internals may account for this also. Maybee possible to store tubes in a vacuum chamber that you could periodically pump down to keep them good!??
     
  3. WA7PRC

    WA7PRC Ham Member QRZ Page

    KM1H s'plained the problem w/ some Eimac 3-500Zs here (link):
    "Eimacs 86-89 had bad seals and welds all due to QC problems at the new SLC plant; the welds were due to trying to save money by using only 3 spot welds.
    I dont have the actual date code groups handy."

    IIRC, there was also concern that early Chinese-made 3-500Zs weren't pumped down as far, and wouldn't hi-pot as high as early US-made 3-500Zs. The pair that came to me in 1975 (in my Heath SB-220) lasted 'til cockpit error caused a failure, about 30 years later. The next (new) pair from China lasted only 6 years before one arced.
     
  4. KA9JLM

    KA9JLM Ham Member QRZ Page

    Tubes should be vacuum packed.
     
    KJ4YEV likes this.
  5. K8ERV

    K8ERV Ham Member QRZ Page

    I think he was pulling thyne leg.

    TOM K8ERV Montrose Colo
     
    N8VIL likes this.
  6. WB2WIK

    WB2WIK Premium Subscriber QRZ Page

    Problem with the Chinese tubes is I'm hungry again an hour later.
     
    WA7PRC likes this.
  7. WA7PRC

    WA7PRC Ham Member QRZ Page

    BTW, the date code looks like this:
    [​IMG]
    (click for bigly image)
     
  8. KA5ROW

    KA5ROW XML Subscriber QRZ Page

    When I was a kid Got a chance to pop several tubes "old TV's in a barn". So what was the smell? I thought it was a argon gas or something.
     
  9. K1ZJH

    K1ZJH Ham Member QRZ Page

    Probably the gettering material that was fired to remove excess gas during manufacture.
     
  10. KV6O

    KV6O Ham Member QRZ Page

    And gassy.
     
    KD2ACO likes this.

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