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Understanding Vacuum Tube Diagrams?

Discussion in 'General Electronics' started by Chris Cooper, Nov 10, 2003.

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  1. Chris Cooper

    Chris Cooper Guest

    I've got an old wire record I'm trying to revive (see my "Reviving 50+ year
    old Wire Recorder" post), one of the problems is that I don't quite
    understand how to interpret the schematics for the vacuum tubes. Is there a
    simple explanation (online preferably) that talks about the "standard
    symbols" used in vacuum tube internals?

  2. Robert Baer

    Robert Baer Guest

    The reference that Jack gave is good for theory, but does not appear
    to relate diagram(s) with terminology.
    It is getting too late for me to scan some info for you; here is a
    "quickie" ASCII pseudo-art:
    _______ <--- plate (crude)
    ----- - - - - <---- grid (sort-of crude)
    | ^ | <---- cathode (crude)
    | / \ <-------- filament
    | | |
    | | |

    Have data on a large number of tubes and can scan what i have for you.
    Will see if i can find something better Monday evening (later today).
  3. GPG

    GPG Guest
  4. tiger x

    tiger x Guest

    A real simple explaination of vacuum tubes:
    1. The source of electrons is the cathode.
    2. To release electrons, the cathode must be heated by the filament.
    3. Released electrons must be attracted & gathered up by the plate.
    4. The flow of electrons through the tube is regulated by the control
    5. Any other grids in the tube are for effecient operation of the
    6. The cathode has a negative potential.
    7. The plate has a positive potential.
    8. The control grid potential varies according to the input signal.
    9. On a schematic, the control grid is the bottom grid and enters on
    the left of the tube.
    10. The signal out of the tube usually leaves via the plate (top), but
    may leave via a resistor connected to the cathode (bottom).

    Easy as that!

  5. Dbowey

    Dbowey Guest

    1. The source of electrons is the cathode.
    Unless the tube has no "cathode." Older tubes used the filament as the negatve
    element, so AC could not be used for the filament voltage, for hum

  6. JeffM

    JeffM Guest

    Tube rectifiers still do.

    The classic H-K short (heater-to-cathode) can also cause hum,
    defeating this design consideration.
  7. Dbowey

    Dbowey Guest

    jeffm posted
    *some* Tube rectifiers do, not all do.

    When did we change over to discussing defective tubes?
  8. Mike Eno

    Mike Eno Guest

    Man you must be a young buck not to know about vacuum tubes ;) or i'm
    an old #art. Wet behind the ears but interested in 50 year old vintage
    electronic devices, all right then.
    I know this is a late response but ...
    Vacuum tubes share a lot of similarity to Depletion mode MOSFETs in
    terms of the design equations. Mind you tubes require much higher DC
    operating voltages plus the aformentioned filament juice.
    Source Gate Drain are analagous to Cathode Grid Plate.

  9. Robert Baer

    Robert Baer Guest

    ....and....i, as well as others posted labelled drawings and links to
    numerous references.
    Dead issue by now.
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