3-500 Tube Life

Discussion in 'Amateur Radio Amplifiers' started by VK4TUX, Dec 2, 2011.

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  1. AG6K

    AG6K Guest

     I have no interest in making mo' money and I am too damned old. Another issue is amps falling into the hands of miscreant Amateur Radio operators.
    . The last amplifier project I started is partly finished and it's currently for sale. The 9kv power supply is pretty much finished. The tube is a tetrode with handles that has 20A of peak emission and low distortion. It's not very practical but a 20db ultra-linear amplifier is a fun project.

    It's still hard for me to believe the size of the hornet's nest I knocked down with the QST Magazine article: "The Nearly Perfect Amplifier".
    • Rich, ag6k
  2. W8JI

    W8JI Ham Member QRZ Page

    That's what happens when a review process fails, like it did with the filament voltage article and the Nearly Perfect Amplifier article.

    It is unfortunate for the author, and even for those correcting or pointing out the published misinformation.

    The only one who suffers minimal damage is the magazine who failed to do proper pre-publication review. Everyone else takes the hard hit.

    73 Tom
  3. KC9TNH

    KC9TNH Ham Member QRZ Page

    Sue, you crack me up. All I want after making it through the holiday expenses is an AL-80B (which is why the original ACTUAL thread title caught me). If I can live long enough to have to replace the tube then I'll have been Blessed indeed. Thanks for perspective. My plan is to simply follow directions, tune it to the max, not overdrive it with the rig, not underload it and, maintaining proper plate & grid thresholds, like a '66 Malibu, drive it like it was stolen and enjoy it. My grand-daughter has a big jar she'll take care of, so I'll ask her to start a $4/week escrow fund for the replacement tube - if I go first she can have the dough.

    Merry Christmas
  4. AG6K

    AG6K Guest

     The article was reviewed by QST Staff. Paul Pagel and Russ Healy told me they liked it. People wrote letters to me and the magazine saying they liked the article. The people who objected after the article was published were mostly either in the Ham amplifier business or had pals who were. One month after the critique was published in Technical Topics, MFJ-Ameritron took out a 10-full page ad in QST. The laugher is that a few months after the critique, I heard that 3 of the experts lost their jobs.

     In the end the truth wins.

     The person who took the hit is the one who tried in vain to obfuscate section 6.11 in Care and Feeding of Power Grid Tubes -- but he doesn't realize it.

    73 Tom[/QUOTE]
  5. AF6LJ

    AF6LJ Ham Member QRZ Page

    You do that and that tube will outlive you easily.
  6. AG6K

    AG6K Guest

     One never knows when Susan. I was supposed to be out of here in 1996, but I'm still breathing.
    cheers, Rich
  7. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    Rich, I visited you in probably 1989. You probably don't remember that, but I do. I just dropped by to pick up some telephone RFI filter kits and found your place in the dark, which wasn't that easy to do.:eek:

    BTW the filters worked FB and cured a few neighbor problems.
  8. AG6K

    AG6K Guest

     For a TL-922 it takes about 55-cents worth of TFE hookup wire. For a 1KD-5, 70-cents. For a SB-220, zero.

     Somewhat difficult for those who do not know how to solder.

     How long a Th-W filament will emit is a matter of filament volts running hours, and how deep the carburized layer is. There is no fixed period. Hams I know who do broadcast transmitter maintenance typically get 22k-hours by riding herd on filament potential.

     Factory-stock 1KD-5 amplifiers get under 150-hours per 3-500Z. Would you be ok with this Susan?

     I have never heard of a 3-500ZG fail from thermal cycling.

    • Rich, ag6k
  9. AF6LJ

    AF6LJ Ham Member QRZ Page

    From what I remember your health wasn't that great for a while.
    I had wondered what had happened and was pleased to hear you on the air a while back.

    in regards to thermal cycling;
    that's always an issue where dissimilar materials are used.

    In the October 2011 QST article referenced in this and other threads the author's journey started with a 3-500ZG that had a filament failure, most likely a bad weld. Now that nobody outside of China are making those tubes and Chinese tube makers are known for producing a less than high quality product I would suspect we may be seeing more mechanical defects rear their heads as the tubes are pressed into amateur service. I could be all wet; somehow I don't think so, only time will tell.
    Last edited: Dec 8, 2011
  10. AG6K

    AG6K Guest

     I remember someone dropping by to buy telephone RFI filters in the early days but I do not remember their name.
    • Rich, ag6k
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