Yet another L4B rescue

Discussion in 'Amateur Radio Amplifiers' started by W9JSW, Apr 13, 2018.

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  1. AI3V

    AI3V Ham Member QRZ Page

    Could you kindly point out where eimac recommends "gettering" in the link you just posted?

  2. WA7PRC

    WA7PRC Ham Member QRZ Page

    Q: Could you kindly point out where in my post I stated "gettering" is in the link I posted three days ago?
    A: I didn't. I stated only:
    Note that my reference to the datasheet was only for the value of HV withstand.

    Last edited: Apr 16, 2018
  3. AI3V

    AI3V Ham Member QRZ Page

    No Bryan,

    Gettering is a process done at the time of tube manufacturing.

    Once you loose vacuum, it's gone. You get the vacuum back by opening up the tube, and putting the tube back on the vacuum pump(s)

    You will not be able to find a single published procedure from any tube maker that tells you to "getter" their tubes.

  4. WA7PRC

    WA7PRC Ham Member QRZ Page

    KM1H likes this.
  5. KM1H

    KM1H Ham Member QRZ Page

    Rege amazes me that he knows so little about the subject but is obsessed about proving it to others.

    WB1E likes this.
  6. AI3V

    AI3V Ham Member QRZ Page

    There is a big difference between building amps for cb'ers and 75m ragchewers, and building and maintaining them professionally.

    Personal attacks vs links to actual manufacturers recommendations notwithstanding.

    Good day gentelmem, the bowl is on Ch 6.
  7. AI3V

    AI3V Ham Member QRZ Page

    Carl, you do realize I have worked on tubes that came with a BOX OF SPARE FILAMENTS!

    And I have changed my share.

    Exactly how many tubes have you "pumped down"

  8. WB1E

    WB1E Ham Member QRZ Page


    Congrats on having a L4B. A couple of things, first off, familiarize yourself thoroughly with both the power supply schematic and the RF deck if not already you have done so.

    As far as operating the Amp on 125V and have it wired for 240v, should not be tried, mainly due to the blower can't blow hard enough to push much air. Speaking of that blower, push on the wheel, and see if it crumbles in your hand. See my previous thread for where to find a new one. The blower runs off T-1 in the RF deck.

    Also note the average condition of the low voltage connector female pins.

    My soft start used a 12 volt switcher that comes with a 2 second delay, combined with a 30a/240Vac solid state relay and 20 watt 300 Ohm resistor. I hope the "other" thread does not corrupt the process here too much~hi.

    As far as "gettering" the tubes is concerned, there is much concern regarding the typical shelf life of the 3-500 design. Here, we are attempting to test 2 things at once. The Amp & the tubes. Try this: simply run the filament ONLY. For many hours. Remove the jumpers in the power supply, and make sure the blower is in good condition and running correctly and the bottom of the RF deck is installed. Also inspect the socket pins and post pictures here if you think you have a questionable one or two as this issue is one of the main reasons for initial failure. After speaking to RF Parts (Merit), he spoke of most of the outstanding failures due to pin overheating pins and sockets. He also will gladly test your tubes for you free.

    Rege my friend...your "elmering" is more like "gettering" Hi. Hang in there Gov.

  9. W9JSW

    W9JSW Ham Member QRZ Page

    Hi Doug,

    Thanks for the reply. Your thread is a virtual cornucopia of details on the amp! Excellent reference. Thanks so much for creating such a valuable resource on your journey of discovery.

    Mine will be a bit different. The amp has tubes that are believed to be good, but no PS. It is complete in every other aspect. So far I need a Plate knob and to replace the red indicator light. Since it does not have the supply, i was able to buy a new cinch-jones female connector on the 'bay. Was only $10. Not too bad!

    Right now I am conversing with Lou on his use of a SB-220 transformer as a basis for the supply. Remains to be seen what my final result shall be. In the mean time, I plan to install a soft-start/soft-key/bias board from Electronic Specialites as sold by Harbach. Will probably also use the PM-400 Drake diode/cap board. Right now I am getting ready to solder the grids directly to ground using some copper strips I bought at Hobby Lobby.

    So I guess I may wire up the connector with Ac so I can run the filaments. About all I can do now until I get the PS sorted out.

    I am on the hunt for a PS enclosure as well. I want all of the dangerous HV to be properly ensconced within a safe enclosure. I am not using the bleeders, so heat should not be as much of a factor.
  10. AI3V

    AI3V Ham Member QRZ Page

    It's your ball Doug,

    Please be so kind as to tell us what measurements you would take before and after "running the filament for many hours", and how would you expect those same measurements to change?

    How do you determine when "many hours" is either enough, or a waste of time?

    To the op, watch for cooling air,plate dissapation, and the condition of the tube socket filament pins.

    The majority of 3-500 z amps I have repaired failed because the filament pins got hot enough for the solder to run out.

    Tune for red heat at your own risk :)


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