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scavenging vacuum tubes

Discussion in 'Misc Electronics' started by Allan Adler, Jun 17, 2006.

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  1. Allan Adler

    Allan Adler Guest

    Vacuum tubes have largely been replaced by solid state devices. I know
    that one can still purchase vacuum tubes and their sockets. What I'm
    wondering is whether it is still possible to scavenge vacuum tubes from
    things that people throw out and leave on the street for trash pickup.
    If so, what things would be likely candidates for scavenging vacuum tubes?
     
  2. Guest

    When I was young I used to do that, I had a huge box of them by the
    time I was 16. Sadly when I reached 20 I had to chuck them. They make
    good targets if you have a pellet gun.
     
  3. Guest

    Allan, is this something that you are interested in for fun or for
    profit? If for profit, most scavenged used tubes are not woth the
    space they take up in storage. Some are.

    Forget anything that you find in an old TV set, since the tubes in them
    are essentailly worthless even if they are still alive.

    Old radios are quite another issue, and by old I mean prior to 1940 and
    preferably battery powered such as the old Atwater Kents and their ilk.
    Even used tubes from early Philcos are in demand by restorers. Tubes
    from these old guys, whether working or not are very collectable.

    Imaging tubes from old TV cameras are also very collectable,
    particularly image orthicons, ikonoscopes and earlier designs.
    Collectors buy these and make display items out of them. Today,
    depending upon their rarity, this type of tube will sell for at least
    $100 and frequently more. Yuppies who were born well after these tubes
    were obsolete seem to get pleasure from displaying them on their desks.

    Grab onto anything unusual. Large old transmitting tubes for example.
    The larger and more interesing, the better. Ionization type vacuum
    gauge tubes are also very popular, if you can snatch them from the
    hands of aspiring physicists. :)

    Kindest regards, Harry C.
     
  4. Allan Adler

    Allan Adler Guest

    Purely for fun and experimentation.
     
  5. Allan Adler

    Allan Adler Guest

    The only substantive reply to my question was based on the assumption
    that I was looking for valuable or rare tubes. I just want to get a few
    tubes to experiment with. I still don't know where I can find them by
    scavenging contemporary discarded electronic devices. Are they really
    no longer scavengeable? If so, I'm aware that one can still purchase
    tubes from contemporary suppliers and that they aren't expensive. I'd
    just rather get them by scavenging them.
     
  6. At this point, you will come across very few discards lying on the sidewalk
    that have tubes in them. It's well past the time, decades ago, when
    people were still routinely using them, so they've long been tossed out.
    People would toss them because the equipment had broken down and it was
    no longer worth repairing, or toss them because they'd rather switch
    to solid state equipment.

    What remains is not likely to be tossed, because enough time has passed
    that people would now see them as collectables. The owners will mostly
    know that it is valuable in some way, be it money or just rarity at
    this point.

    That's not to say you won't see the occasional tv or radio that uses
    tubes, but it will be quite rare. I think it's been about a decade
    since I came across a tv or radio that had tubes in it. I did see
    a couple of oscilliscopes a few years back that had to date from
    the tube era, but you aren't likely to see those in the garbage very
    often, whether they have tubes or don't.

    Keep in mind that in the tube era, the average household have very
    little electronic equipment. A tv set or two, a radio or two, and
    maybe some sort of stereo system (or just a portable record player).
    There just wasn't the level of electronic gadgetry back then. It
    was the coming of solid state, and especially of ICs, that made
    it feasible to get a lot into a small space, which meant a lot
    of new consumer items. The IC and microprocessor became so
    cheap that not only were there a lot more gadgets around the
    house, but even pretty dumb things had clocks and such built in.

    35 years ago, when I got interested in electronics, I never
    saw much more than tv sets and radios waiting for the garbage trucks.

    Even if you do come across such things, many of them were "AC/DC",
    ie they ran right off the AC supply with no transformer, and in
    order to do that they ran the tube filaments in series, and in order
    to do that the tubes would have different filament voltages that
    when added up would require little or no dropping resistor from
    the AC line. So even for experimenting, the tubes from such
    consumer equipment weren't so useful, because you'd not be
    duplicating the tube lineup, and then would have to fuss with
    a 50 volt filament for that tube, and a 35 volt filament for
    that other tube, and so on.

    Michael
     
  7. Allan Adler

    Allan Adler Guest

    That's what I thought. The advantage of finding tubes and experimenting
    with them, instead of buying them, is that I don't have to know what I
    want: I just have to be willing to work with what I have. So, now I
    guess I have to figure out what I want.

    A few months ago, I passed a church and noticed that they were throwing
    away an old electric organ. About a mile away from there, I saw another one
    being thrown away in front of an apartment building. I was of course tempted
    to drag them through miles of streets to my apartment but then realized that
    they were probably inferior to the synthesizer keyboards selling for $200.
    In retrospect, I'm now wondering whether they might have had some tubes
    in them.

    Anyway, getting back to what I want, the Franck-Hertz experiment is
    performed using a mercury-filled tube (I think a pentode) made by the
    Leybold Company (55580), according to Melissinos, Experiments in Modern
    Physics. If you actually buy this tube from Leybold, I think it costs
    hundreds of dollars. They might have a version that is especialy suited
    for doing the experiment in physics lab courses.

    So, maybe what I want is an inexpensive mercury-filled pentode that I
    can either use to do the Franck-Hertz experiment or about which I have
    enough data on to prove that I can't use it to do the Franck-Hertz experiment.

    Any suggestions?
     
  8. The only mercury tubes I recall were high current rectifier tubes made
    in the 30's. I do not remember any other radio/TV application that
    would use those. You might look at HAM radio gear those tubes...

    John :-#)#
    --
    (Please post followups or tech enquires to the newsgroup) John's
    Jukes Ltd. 2343 Main St., Vancouver, BC, Canada V5T 3C9 Call
    (604)872-5757 or Fax 872-2010 (Pinballs, Jukes, Video Games)
    www.flippers.com "Old pinballers never die, they
    just flip out."
     
  9. George

    George Guest

    Check out any Hamfests in your area, go to http://www.arrl.org and
    search hamfest calendar
    ask the vendors and guys with swap tables. Also talk to the owners of
    any local pawn shops and people that handle estate sales and such,
    these people find lots of stuff in attics and basements, if it's in bad
    shape or they have no market for it it often goes to the dump. I've
    come across a lot of neat finds just by offering to clean out an attic,
    basement or garage in exchange for the right to keep what I want.

    George
     
  10. The specific tubes you are looking for I've never heard of, so I'd say
    chances are zero that you'd ever stumble on them at random.

    But to get to the organs, that's why you should always carry some small
    tools around with you. SOmetimes it's worth bringing things home intact,
    but especially after you've done it a few times you find you have lots
    of common parts but not much of the rarer parts. At that point, it's
    worth having some screwdrivers and maybe a nut driver, and some cutters,
    so when you see a tv set you can pull the back off to grab the important
    parts (or in your case to see if there are any tubes), or you can open
    that radio to get the variable capacitor off. Sometimes it's worth pulling
    the whole circuit board, but still that's easier to get home than bringing
    the whole unit when you plan to throw out most of it when you get home.

    The last thing I need to bring home is another computer, unless it somehow
    beats what I already have (and that's not going to happen for a while), but
    with the tools I can quickly get the case off and see if I should pull
    the RAM and the hard drive.

    One time I found something that had used Nixie tubes, but the Nixies were
    missing. Made me wonder if the original owner had taken them out, or
    if someone had gotten to them already. That seems to happen fairly often,
    that something is missing.

    Michael
     
  11. If you can find a working Hammond organ, those are worth big bucks!
    All the pentodes I ever saw in TV sets, radios, stereos, and musical
    instrument amplifiers are vacuum ones.

    The only gas tubes I ever saw were a few regulators and a few
    rectifiers, and never in a junked TV.

    Meanwhile, I Google for "Frank-Hertz experiment" and the first hit shows
    a schematic that makes the tube look like a triode.

    - Don Klipstein ()
     
  12. Allan Adler

    Allan Adler Guest

    Thanks for the suggestions. I've heard so much about toxic stuff in attics
    (e.g. fibre glass, asbestos) and other repositories that I'm a little afraid
    to go that route. But hamfests are a possibility.
     
  13. Allan Adler

    Allan Adler Guest

    Yes, it does. One of the hits makes it look like Franck and Hertz used
    a mercury filled triode and one at the Univ. of Rochester also seems to
    use a mercury triode. Elsewhere I found the Franck-Hertz tube described
    as a thyratron. Maybe that terminology will make it easier to figure out
    what to get and from whom.
     
  14. Allan Adler

    Allan Adler Guest

    That's a good idea. I'll start doing that.
     
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