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Holes in Plates

Discussion in 'Electronic Design' started by Phil Allison, Sep 23, 2005.

  1. Phil Allison

    Phil Allison Guest

    Reposted from "rec.audio.tubes" :


    ** Why do some plate structures in power tubes have holes.


    A quick survey of my own stock showed:


    6V6GTA Sovtek = no holes

    5881 Sovtek = 4 vertical slots

    6L6GC Sylvania = no holes

    6CA7 Sylvania = 6 round holes

    6550C Svetlana = 6 horizontal slots

    6L6 WXT Sovtek = 6 round holes

    EL34 EH = 4 horizontal slots


    In each case, the holes are exactly aligned on opposite sides of the plate
    with the cathode structure on axis.


    Please do not suggest it is for ventilation or cooling ;-)




    .......... Phil
     
  2. Paul Burke

    Paul Burke Guest

    Presumably the ones without holes only use electrons.
     
  3. Tim Shoppa

    Tim Shoppa Guest

    In each case, the holes are exactly aligned on
    I'm not familiar with those particular tubes you mention, but beam
    power tube plates are often made of two different pieces that are
    attached to each other by bending tabs in piece "A" through slots in
    piece "B". I see this in several 807's and 6146's I have on my desk at
    the moment (they're usually RF tubes, not audio, but they are beam
    power tubes.)

    These holes usually aren't in the parts getting the beam but are
    external. I mean, you cannot see the cathode through the holes, you
    just see out the glass on the other side.

    If you look at the holes (look at both sides!) do you see any such
    attaching-two-parts tabs in your tubes?

    Tim.
     
  4. Phil Allison

    Phil Allison Guest

    "Tim Shoppa"

    ** The holes are squarely aligned.

    The cathode is visible in each case.



    ............ Phil
     
  5. Jim Thompson

    Jim Thompson Guest

    Sno-o-o-o-ort!

    Perhaps the holes are to let AIR flow through ?:)

    ...Jim Thompson
     
  6. The holes may help prevent the formation of hot spots - just a guess.
     
  7. Hurricane lamps?
     
  8. To reduce deformation due to heat?
     
  9. .... to reduce the cyclic stresses and metal fatigue caused by such
    inevitable deformation during uneven heating. A correctly placed
    perforation can greatly reduce the chance of metal cracking.
     
  10. Wasn't thinking of that - perhaps to make the valve more linear by creating more paths for the current to avoid saturation effects.

    But I moved from valves to transistors when I was 13 - there must be some older folks here who actually know the answer !
     
  11. Jim Thompson

    Jim Thompson Guest

    I was just about to opine that myself. Seems logical that alignment
    could be heat-dependent.

    ...Jim Thompson
     
  12. Reg Edwards

    Reg Edwards Guest

    ** Why do some plate structures in power tubes have holes.They may have been used for location purposes during the forming
    process. It's a precision form of construction.
     
  13. Jim Thompson

    Jim Thompson Guest

    On Fri, 23 Sep 2005 16:41:07 GMT, richard mullens

    [snip]
    That's about the age I made the move ;-)

    ...Jim Thompson
     
  14. Pooh Bear

    Pooh Bear Guest

    For jigging in assembly ?

    Graham
     
  15. Guest

  16. Jim Thompson

    Jim Thompson Guest

  17. Since we're all guessing, I'm going with thermal stress relief. :)

    Or, since the plates are made of a special alloy of mysterium and
    unobtanium, it's to save material to make more anodes with - maybe
    they use the little circles to make nuvistors!

    Cheers!
    Rich
     
  18. No, no, no! It's those little disks at the ends of the filament
    in that split-anode 5C39 or whatever it was! Yeah, that's it!

    Cheers!
    Rich
     
  19. Fred Bloggs

    Fred Bloggs Guest

    Nah- it was discovered early on that the holes reduce secondary-emission
    and its noise effects- all of this is late 19th century stuff.
     
  20. Fred Bloggs

    Fred Bloggs Guest

    They're not called "holes" BTW- it is perforation.
     
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