Not excatly an electrical question. However, I recently got a hold of 3 old tube testers. 2 are in wooden boxes with covers and one is in in a metal box with no cover. Does anyone know anything about these? They have a scroll built into them with all the different tubes listed and what to set the switches at to test them. I can get make and model if that would be helpful.
I thought they were rather interesting pcs.

Can you get some pictures?
We'll post them here.

If so, send them to:
photos@Electrical-Contractor.net

Bill

What exactly do you want to know about them?

Tube testers fall into 2 general categories: emission testers and mutual conductance testers.

The emission testers were much cheaper, simpler, and more limited in their usefullness. They would identify a tube that was burned out or completely used up, but that's about it. Cheaper TV service testers, as well as the once ubiquitous drugstore self-serve testers were all emission type. They basically tie all the elements except the cathode in the tube to the plate, and test the tube as a simple diode. They can actually damage some low-power tubes by forcing too much current through the grids.

Mutual conductance testers are much more sophisticated, and give a better picture of tube quality. They generally set the tube up as an amplifier, and measure the change in plate current caused by a change in grid voltage (transconductance or Gm). These testers were more complex to set up (lots of switches and knobs!), but could find more subtle tube defects than a simple emission test.

If you can post makes and model numbers, I can probably tell you what type you have. A great reference on tube tester technology is "Tube Testers and Vintage Electronic Test Equipment" by Alan Douglas. The author (as well as a few ECN members including myself) are regulars on the USEnet newsgroup rec.antiques.radio+phono, which is a great resource for questions on tube era equipment.

Sure, but when playing with them, keep in mind they have a high voltage (sometimes up to 800v) for the heater portion of the tube. The low voltage parts act like the collector, emitter, and base (or valve/gate) of a transistor. Once the base is heated up to the point that it can emit electrons internally, the various switches on the tester change the bias on the gate and allow (or stop) signal to pass through.

Most of the guys that have one (or some) of these usually clean them up and park them in some unused part of their lab/office. Sort of a novelty wall hanger.

(mho) Not a lot of current-day use unless you are into old time radio equipment, or maybe some sort of Dale Gribble survivalist.
Some of those guys keep old tube radios and equipment around for the day the Commies (etc.,) (insert favorite boogieman) attack.

I guess if you wish to find the market/values I would look on ebay and other such sites.

See you,

Phil

I have an old one, a Swan I beleve, that was once owned by the Navy.

The heater of a tube generally operates on LOW voltage (typically 6.3 VAC), although a handful of types operated directly from 117V line voltage.


Actually, being a voltage-operated device, a tube is more analogous to an N-channel depletion mode MOSFET than a bipolar transistor. The element correspondences would be cathode=source, grid=gate, and plate=drain. And in most tubes, the plate is anything but a "low voltage" element, operating at hundreds or even thousands of volts!


On a bipolar transistor, the base would be analogous to the GRID, not the heated cathode, which is the electron source. The emitter would be the equivalent to the cathode.


Mine sees somewhat regular use, but I restore old radios and test gear as a hobby. I also collect tubes themselves (mostly big transmitting types) as another aspect of the hobby.


[This message has been edited by NJwirenut (edited 08-29-2003).]

The best place (among others) to go for information is the Antique Radio + Phono UseNet news group.

It's accessible through http://groups.google.com -- just type rec.antiques.radio+phono in the box. You have to subscribe to post but it's no big deal.

By all means post the pictures here (or on a separate website) -- and you can steer the people there to look for them at the website since you can't post pictures on that newsgroup.

Good luck!!!

Wirenut,
Don't you just love the smell and crackel sounds of old tube equipment.
WB2OMS

Absolutely. The older equipment has a "soul" that modern solid state stuff somehow lacks.

Just about to begin restoration work on an R-390A/URR HF receiver. A masterpiece of tube era engineering. Digital frequency readout using an odometer-style counter and more gears and cams than a automotive transmission. Should be lotsa fun!
http://www.r390a.com/index.htm

Real Radios Glow in the Dark!
http://www.ominous-valve.com/tubes.html

73,
Bob N2IXK

Well said, Sir!

Regulars here will know that I'm also a fan old of equipment and often have tube radios, amplifiers, etc. that I restore.

These tube testers (or in British terminology, "Valve testers") come in many varieties. Some of the most sought after in Britain and the series made by Avo. Some models sell on eBay now for figures well up into three digits.

As for the voltages involved, I'll just echo what others have beaten me to saying. The plate voltages, especially on high-power tubes can be high, and testers designed for those tubes will output HT at hundreds of volts and a good few ten of milliamps, so be careful!

Famous Last Words #287: "Of course the top cap is the grid!"

When I moved last year,there was no place for some of the old radio gear so it went in the junk. I did try and auction some but freight was prohibitive. I had an old commercial two way that used lighthouse triode final output tubes. The power supply used mercury vapor rectifiers that put out 2000 volts at 1/4 amp. It would light up a whole room then it was keyed.

My first build project was a CW that used a No. 80 I worked more stations with that home built then any unit since. Most of the tubes I used came from the junk pile. Today this would be a pile of gold.

Just imagine a GCFI using vacuum tube technology..... :-)
Or a smoke detector....

Actually, given that they want you to replace smoke detectors every ten years, some vacuum tubes could last that long in continious use.

OK tube guys I have a question, why do the tubes get more "purple" as the load goes up?

When I was about 16 I had agreed to provide a PA for a party, what I rigged up was a pair of I believe Stromberg-Carlson 200 watt tube amps.

I used one for each channel and drove 4 speakers off of these no problem with a lot of volume. These amps had 4 ohm to 49 ohm (70V) outputs.

While in use I noticed that as the Bass hit the tubes color seemed to change.

Also

A nice set up I saw when I was about 5 or 6 was a tube radio set I think it was made by Scott and it was in separate chromed components, a distant Vermont farmer cousin had it in his living room and used it daily, even then I knew it was something cool.

Dose any of this make sense?

Bob

A colored glow inside a vacuum tube can have 2 different causes. Residual gases inside the envelope usually cause a bluish/white glow INSIDE the plate structure, caused by the electron streams ionizing the gas molecules. This kind of glow is a pretty strong indication that the tube is shot, and generally causes some kind of defect in circuit operation.

A purplish blue glow on the inside of the glass envelope is often seen in power tubes, particularly those operating at higher voltages. This is not a cause for concern, and can actually be an indicator of better than normal vacuum. The cause are stray electrons hitting the envelope, where they cause trace impurities in the glass to fluoresce. Because the intensity of the electron beams inside the tube varies with plate current, the position and intensity of the glow will "dance" with the signal being amplified. In an audio amp or modulator, you get a nice little "light show" effect.

Some types of tubes (voltage regulators, gas/mercury rectifiers, thyratrons, ignitrons, etc.) contain various gases which will emit a characteristic glow during normal operation. The color depends on the fill gas, with argon producing a violet glow, mercury vapor giving a hazy blue, xenon a white/blue glow, and neon the famous orange-red.

[This message has been edited by NJwirenut (edited 09-01-2003).]

[This message has been edited by NJwirenut (edited 09-01-2003).]

The glow produced by the OB2 voltage stabilizer (cold cathode) I always find rather attractive!

Another thing you might notice inside the glass envelope of some tubes is a metallic-gray looking deposit at some point. This is quite normal and a consequence of the way the tube is manufactured.

A milky-white deposit on the inside of the glass, however, is a bad sign, and generally indicates a leaky seal, rendering the tube useless.

There are a few tube testers on this link, along with plenty of other test equipment:
http://www.thevalvepage.com/testeq/testeq.htm


[This message has been edited by pauluk (edited 09-02-2003).]

I remember building a tube tester in kit form from Allied Radio. I thought it was the coolest thing in the world for having a tapped filament transformer good from 1.5 to 117V(!)

It was handy too, for having an number of military tube numbers, and you got to use a piece of solder to jumper plate and grid connections on a few.

first project was a VTVM Kit then on to the Tube tester kit. I wonder what that transformer would cost today. reworking an SCR522 was a real trip, and they were a real night show, and provided heat for the cold winter nights.

That metallic deposit is called a "getter flash", and consists of barium or other reactive metal. Intended to adsorb any stray gas molecules which survived initial pumpdown, or which might be liberated from the internal elements during the life of the tube.

When the tube develops a crack, the oxygen in the air reacts with the getter to form a white deposit of barium oxide.

Flash getters are deposited on the inside of the bulb by heating an internal metal "pellet" with an induction heater just after the tube is sealed off from the vacuum pump. The support that once held the getter pellet is visible just behind the getter flash. It often looks like a metal ring or bar.

Internal anode transmitter tubes used a different gettering scheme. They used a tantalum/zirconium alloy for the anode material, which adsorbed gases quite strongly when in operation. The gettering operation required the anode to operate at a red-hot temperature, though! Such a tube will quickly develop gas unless operated at sufficient dissipation levels.