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aluminum foil on TV screen

Discussion in 'Misc Electronics' started by Allan Adler, Sep 10, 2006.

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  1. Allan Adler

    Allan Adler Guest

    At http://www.amasci.com/emotor/tvgen.txt they claim that one can generate
    the high voltages one needs (thousands of volts) for a plastic soda bottle
    motor by taping aluminum foil to one's tv screen and repeatedly turning
    the tv set on and off. They recommend that one use a tv one is not planning
    to rely on for long because apparently the act of turning it on and off
    repeatedly eventually breaks the TV set.

    I don't know much about TV sets but it seems to me that if you turn the
    set on and off as often as they suggest, the most likely thing to break is
    the on-off switch. In that case, one preventive remedy would be to plug
    the tv set into a power strip with its own on-off switch, turn the tv on
    and keep turning the power strip on and off. If the power strip wears out,
    at least the tv still works.

    The other thing I was wondering was whether, since the high voltages originate
    inside the tv set in the first place, whether there is a convenient way to
    reroute some of the internal circuitry of the tv set to use as a high voltage
    source. For example, the tv tube has a plug with wires going to it and a
    big wire going into a splotch of plastic somewhat closer to the tv screen
    (I'm not looking at an open tv as I write this; I'm drawing on vague
    recollections of having taken at least one tv set apart that I found on
    the street a couple of decades ago.). So, if one unplugged the plug at
    the back of the tv tube and cut the big wire going into the splotch of
    plastic, maybe those would provide the leads one needs to use for the
    high voltage power supply. I'm aware that one isn't supposed to poke
    around inside tv sets and I have no plans at the moment to do anything
    that I'm describing. I'd just like to know in principle whether something
    along these lines would work.

    In the book of Gilardini I mentioned in another posting, he says that
    one way to get precision high DC voltages is to use special batteries.
    Any idea what kinds of batteries he might be talking about and how much
    they might cost (not that I'm planning to rush out any buy them)?
     
  2. They aren't designed for that and it seems like a stupid and dubious method.
    A Van de Graaf generator is not that hard to make

    See http://www.hobbytron.net/Van-De-Graaf-Generator-Kit.html amongst others.
     
  3. jasen

    jasen Guest

    It's stressful on the internals of the TV
    5000 or so power-cycles sould wear it out.
    That's the one, It probably has a high voltage charge (even when
    the TV has been unplugged for weeks) attach a screwdriver to the bare wires
    that cross the back of the TV using a convenient length of wire and probe
    around under that splotch until you hear all the charge has gone.
    under that splotch is a clip that'll unhook if you squeese it just right
    (use pliers).
    no idea... I don't think there's any sort of chemical battery that can
    conveniently produce thousands of volts.

    Bye.
    Jasen
     
  4. Allan Adler

    Allan Adler Guest

    As I said, I'm not planning to do this, at least not in the near future,
    and in any case I don't have a spare TV set to try it on. But I would like
    to understand a little better what you are saying needs to be done. By the
    bare wires that cross the back of the TV, do you mean those antenna leads
    or are you talking about something else? Actually, this gives me an excuse
    to actually look at a book on TV repair and/or a book specifically devoted
    to a particular model of TV. If there is a way I can get a complete
    schematic for free, accompanied by pictures of the corresponding parts
    of the assembled TV, I can refer to pin down details of what you are saying.

    I've always been afraid of doing anything to cause the TV tube to implode,
    although I did take TV sets apart anyway. I vaguely recall cutting that
    cord on one or more occasions with a pair of pliers, without knowing that
    THAT was the locus that held high charges for a long time after the set
    is turned off. I don't think I realized that one can unhook the big splotch,
    but maybe I forgot after such a long time.

    Anyway, apart from not knowing the site(s) you are referring to in the TV,
    I'm also having a little trouble parsing what you wrote: "... attach a
    screwdriver to the bare wires that cross the back of the TV using a
    convenient length of wire and probe around under that splotch is a clip
    that'll unhook if you squeese it just right ". I'm gravitating towards:
    (Step 1) attach a screwdriver to the bare wires that cross the back of the TV
    (Step 2) use a convenient length of wire to probe around
    (Step 3) under that splotch is a clip that'll unhook if you squeeze it
    just right

    but I'm not sure. For example, maybe the convenient length of wire is
    instead supposed to be used to attach the screwdriver to the bare wires
    that cross the back of the TV. Also, with either interpretation, I'm not
    sure what the operation of probing around constitutes.
    I don't know anything about batteries, but maybe they are referring to a
    storage battery or a collection of storage batteries, which one can just
    charge up from a wall socket. In combination, one might get to some high
    voltages.
     
  5. jasen

    jasen Guest

    there'll be some uninsulated wires that contact the back of the picture tube
    typically they're held in place with some springs etc. the outside and
    inside of the picture tube have conductive coatings and form a large
    capacitor.
    That's pretty hard to do. The fragile part of the tube is at the pointy end.
    the rest of it it pretty tough, the front particularly so.

    I've had to chuck rocks at the backs of TV tubes to bust them in the past.
    but I've let "the vaccum out" of tubes by just putting incorrect pressure on
    the circuit-bouard at the back.
    sorry, I editied that paragraph too many times...

    earth the screwdriver by attacing it to the bare wires,
    probe with the screwdriver till you hit the clip under the "sploth"
    thus making a path for the electric charge to take to dissipate safely.

    The clip can then be undone safely if squeezed with pliers,
    but some charge will come back slowly (but much less than the normal charge)
    hundereds of volts only, it sounds like you need thousands.

    Bye.
    Jasen
     
  6. Allan Adler

    Allan Adler Guest

    Thanks for the clarification regarding the TV procedures.

    That's interesting. Why did you want to break a TV tube? I once heard a lecture
    at a meeting of the AAPT wherein the speaker mentioned that he had broken
    a TV tube to obtain the phosphor coated glass for some kind of experimental
    demonstration. I don't remember what he was trying to demonstrate, though.

    I haven't looked at the inside of a TV in over 20 years, so I might be
    hazy in my recollection. I don't remember any printed circuit board at
    the back of the tube. The closest thing I remember to anything at the
    back of the tube is the plug for the tube. But in any case, I'm curious
    about how much control one has over the change in pressure in the tube.
    If you let just a tiny amount of air in, maybe you'll then have a gas
    filled tube that you can try to do experiments in gas conduction with.
    If you put the TV in a big glovebox in an atmosphere of some gas, such
    as argon, maybe you can try to do the Franck-Hertz experiment with it.
    That's probably overly optimistic.
    I've been discussing this on sci.chem and I'm still not sure about
    this point. For ionization of one of the atoms of the gas, presumably
    one needs 1-3eV per atom, but Gilardini is talking about electrons with
    typically 0.1 eV. So, if one needs thousands of volts to ionize a gas,
    maybe for his experiments one only needs hundreds. Also, if there is
    a tungsten filament in the tube, that makes it sound to me more like a
    gas filled tube, such as I find in the RCA tube manual requiring only
    hundreds of volts at the anode. But I really don't know.
     
  7. jasen

    jasen Guest

    I was a curious teenager, I chucked rocks around the corner of the garage
    until I met with success.

    the intact front part of the screen was retained as "saucer" for a large
    pot-plant
    I can't immagine. I think the phosphor oxidises fairly quickly.
    These days there's a PCB soldered to the plug. it has the ampliifiers for
    the red green and blue drive

    But in any case, I'm curious
    It's kind of hard to see inside. most of the back is metal coated.
    Even ion generators (running at normal air pressure) need over a thousand
    volts, you could get there (from ac mains) with a cockroft-walton voltage
    multiplier if you had enough stages in it. (not very safe though)
     
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