For Those Who Think Certain Xmitting Tubes Don't Getter With Rated Plate Temp

Discussion in 'Amateur Radio Amplifiers' started by W2VW, Feb 26, 2021.

ad: L-HROutlet
ad: l-rl
ad: l-BCInc
ad: l-gcopper
ad: Left-3
ad: abrind-2
ad: L-MFJ
ad: Left-2
ad: QSOToday-1
  1. W2VW

    W2VW Ham Member QRZ Page

    http://www.tubecollectors.org/h&k/archives/hk24.pdf

    Second paragraph explains tube gettering using a "cherry red glow."

    EIMAC was started by ex Heintz & Kaufman employees.

    Somewhere is a similar description from EIMAC in an ad but I haven't found it yet.
     
    W4LJ and K0UO like this.
  2. KM3F

    KM3F Ham Member QRZ Page

    The Anode is made from certain metal and compositions.
    During manufacturing, the parts are induction heated to a high tempersture in the 1000 degree range to drive out the gasses stored in the structures and pulled out of the of the envelope by Vacuum extraction, then pinched off.
    Any gasses left or generated is absorbed/attracted into the anode structure when it gets hot during citcuit operation.
    .
    In receiving tubes, the Getter is a different type placed in a ring, then flashed by induction heating usually after pinch-off.. This is the silver you see deposited on the outer wall of the glass and does not depend very much on heat. This type of getter is not desirable for RF transmiting tubes because it does not do well in very high voltages applications and for the capacity effects it causes at higher RF frequency limits.
     
    W9FL likes this.
  3. WQ4G

    WQ4G Ham Member QRZ Page

    In the case of the HK24 the cherry red plate has nothing to do with 'gettering.' This is a rather complex subject with many considerations. The HK24 has a Tantalum plate structure (Anode) which once sufficiently 'gettered' can be consistently operated with a 'cheery red' plate.

    Operating a tube constructed with a Graphite or Molybdenum plate structure at a high 'cherry red' temperature can actually liberate more (and/or additional types of) gas.

    WQ4G
     
  4. W2VW

    W2VW Ham Member QRZ Page

    Obviously the tube needs a gettering process during manufacture.

    It also benefits from continuing deep vacuum.

    Operating below red for long periods of time can shorten tube life.
     
  5. KM3F

    KM3F Ham Member QRZ Page

    Tell me all about it, I use to work in that field for 2 companies.
    From receiving tube to microwave. Klystron to Backwaed Wave plus a lot of other types..
    The last 3-500 were made in a plant nearly in my back yard where I was employed until I moved on.
     
  6. AI3V

    AI3V Ham Member QRZ Page

    Except that's not what is written!

    What is going on is the tantalum is heated hotter than red hot (orange or even white) while the tube is originally manufactured and connected to the vacuum pump.

    During normal operation the anode is never allowed to get that hot, so it never outgasses any more.

    This superheat or "bombardment " is a fundamental and critical part of creating a high vacuum.

    The other problem with attempting to correct a bad vacuum by sammy hammy "gettering" is the tube, more or less cold will not work properly.

    As you attempt to "getter" the rise in temperature will liberate more gas, and this gas will condense on any part of the tube that is cooler than the anode, you have both an electrical runaway condition, and no way possible to heat the glass red (or orange or white) hot to get the gas back into the anode.

    Rege
     
    WQ4G likes this.
  7. W2VW

    W2VW Ham Member QRZ Page

    https://www.thevalvepage.com/valvetek/getter/getter.htm

    Tantalum
    Certain metals are capable of incorporating gases, even noble gases, by solution in their bulk volume. The classical example is tantalum which, on account of this property, plays a predominant role in the construction of high-power transmitting tubes. After degassing in a high vacuum for several hours at a temperature of 1,600 to 2,000 C, tantalum is capable of ab-sorbing gases in amounts up to several hundred times its own volume. The optimum gettering temperature for tantalum appears to be in the neighborhood of 1,000 C. At temperatures above 1,500 C, the gettering action is reversed. The maximum getter effect is secured, therefore, by dimensioning tantalum anodes so that during normal service the electrodes operate at red to yellow heat. Generally, the high price of tantalum sheets and wires limits the use of whole tantalum electrodes to particularly valuable tubes and suggests the coating of electrodes with tantalum powder. This is mostly performed by applying very fine tantalum powder on the surface of anode sheets in the finished assemblies. They are sintered together while simultaneously degassing these powders during the pumping operation by means of high-frequency heating or by electron bombardment On account of the high degassing temperature re-quired for tantalum, only molybdenum or tungsten is suitable as a base metal for tantalum powder. Tantalum should never be hydrogen-fired because of embrittlement and consequent destruction by this gas.

    The main disadvantages of tantalum are the high materialand the high temperature range required for proper degassing and subsequent gettering operation.

    And

    https://hypertextbook.com/facts/2000/StephanieLum.shtml

    Metal Temperature by Color
    Color Approximate Temperature
    °F
    °C K
    Faint Red
    930

    500

    770

    Blood Red
    1075

    580

    855

    Dark Cherry
    1175

    635

    910

    Medium Cherry
    1275

    690

    965

    Cherry
    1375

    745

    1020

    Bright Cherry
    1450

    790

    1060

    Salmon
    1550

    845

    1115

    Dark Orange
    1630

    890

    1160

    Orange
    1725

    940 let's go with this, shall we?

    1215

    Lemon
    1830

    1000

    1270

    Light Yellow
    1975

    1080

    1355

    White
    2200

    1205

    1480


    [​IMG]

    Bibliographic Entry Result
    (w/surrounding text)
    Standardized
    Result

    Faughn, Jerry S., Serway, Raymond A. College Physics: Fifth Edition. Philadelphia: Saunders, 1999. "Wien's displacement law:
    λmaxT = 0.2898 × 10−2 m.k" 555 °C
    "Red Heat." Dictionary of Science and Technology. New York: Larousse, 1995. "As judged visually, a temperature between 500 °C and 1000 °C." 500–1000 °C
    Hodyman, Charles D., Lange, Norbert A. Handbook of Chemistry and Physics. Cleveland, OH: Chemical Rubber Co., 1924.
    Color Temperature
    °C
    K
    Incipient red heat 500-550 770-820
    Dark red heat 650-750 920-1020
    Bright red heat 850-950 1120-1220
    Yellowish red heat 1050-1150 1320-1420
    650–1150 °C
    Process Associates of America. Metal Temperature by Color.
    Color Approximate Temperature
    °F
    °C K
    Faint Red 930 500 770
    Blood Red 1075 580 855
    Dark Cherry 1175 635 910
    Medium Cherry 1275 690 965
    Cherry 1375 745 1020
    Bright Cherry 1450 790 1060
    500–790 °C

    [​IMG]

    Bibliographic Entry Result
    (w/surrounding text)
    Standardized
    Result

    Faughn, Jerry S., Serway, Raymond A. College Physics: Fifth Edition. Philadelphia: Saunders, 1999. "Wien's displacement law:
    λmaxT = 0.2898 × 10−2 m.k" 555 °C
    "Red Heat." Dictionary of Science and Technology. New York: Larousse, 1995. "As judged visually, a temperature between 500 °C and 1000 °C." 500–1000 °C
    Hodyman, Charles D., Lange, Norbert A. Handbook of Chemistry and Physics. Cleveland, OH: Chemical Rubber Co., 1924.
    Color Temperature
    °C
    K
    Incipient red heat 500-550 770-820
    Dark red heat 650-750 920-1020
    Bright red heat 850-950 1120-1220
    Yellowish red heat 1050-1150 1320-1420
    650–1150 °C
    Process Associates of America. Metal Temperature by Color.
    Color Approximate Temperature
    °F
    °C K
    Faint Red 930 500 770
    Blood Red 1075 580 855
    Dark Cherry 1175 635 910
    Medium Cherry 1275 690 965
    Cherry 1375 745 1020
    Bright Cherry 1450 790 1060
    500–790 °C
     
    N0TZU and K2XT like this.
  8. K2XT

    K2XT Premium Subscriber QRZ Page

    Very Weak - Will my L4B 3-500s getter at 150 watts out on 75 meter "yaa yam"?
     
  9. W2VW

    W2VW Ham Member QRZ Page

    It might. Never tried one.

    The people who say old 3-500Zeros with bad seals are hopeless are correct but they don't all have bad seals.

    Besides, your bottles already have plenty of vacuum.
     
  10. AI3V

    AI3V Ham Member QRZ Page

    So how are you going to get the anode that hot without arcover from the existing gas,

    And then without melting the rest of the tube?

    When the tube is on the vacuum pumps, the anode is heated with a induction coil

    After all other parts of the tube undergo a elaborate cleaning process.

    Despite what sammy hammy tube (re)sellers try and convince you, all you are going to do is ruin your amp.

    Your 3-500 developed cracks around the base pins due to mishandling, and the poor mechanical design of the socket.

    And the advice given to "tune for maximum output and ignore plate current" plays a big part.

    Rege
     
    WQ4G likes this.

Share This Page

ad: MyersEng-1