scavenging vacuum tubes

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.

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.

Allan Adler wrote:

Purely for fun and experimentation.

--
Ignorantly,
Allan Adler 
* Disclaimer: I am a guest and *not* a member of the MIT CSAIL. My actions and
* comments do not reflect in any way on MIT. Also, I am nowhere near Boston.

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.

--
Ignorantly,
Allan Adler 
* Disclaimer: I am a guest and *not* a member of the MIT CSAIL. My actions and
* comments do not reflect in any way on MIT. Also, I am nowhere near Boston.

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

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?

--
Ignorantly,
Allan Adler 
* Disclaimer: I am a guest and *not* a member of the MIT CSAIL. My actions and
* comments do not reflect in any way on MIT. Also, I am nowhere near Boston.

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 :-#)#

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Check out any Hamfests in your area, go to

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

Allan Adler wrote:

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

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 ( snipped-for-privacy@misty.com)

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.

-- Ignorantly, Allan Adler

• Disclaimer: I am a guest and *not* a member of the MIT CSAIL. My actions and

• comments do not reflect in any way on MIT. Also, I am nowhere near Boston.

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.

--
Ignorantly,
Allan Adler 
* Disclaimer: I am a guest and *not* a member of the MIT CSAIL. My actions and
* comments do not reflect in any way on MIT. Also, I am nowhere near Boston.

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

--
Ignorantly,
Allan Adler 
* Disclaimer: I am a guest and *not* a member of the MIT CSAIL. My actions and
* comments do not reflect in any way on MIT. Also, I am nowhere near Boston.