Old Vacuum Tubes

Do they have ID numbers? Markings?

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One I already looked up came in a box with the radioactive symbol on it, it was used in power amplification (if I recall correctly).

Biggest to smallest:

G.E.; 807 England; EK 188-5

United Electron; 6F8G

National Union Electron; 6F8G

G.E.; 6C8G

G.E.; 6L6GC

G.E.; 5y3GT

G.E.; 5824

G.E.; 5824; SU 188-5

Then a pair of black (metal?); 6SC7

I will browse the links you posted later when I have time.

Drew K

What are the part numbers for the radioactive ones?

They may be emitters or could actually contain sources.

It is a pretty one, has 3 rods with black balls on the end that seem to touch.

KX 642, Westinghouse

Drew K

Hmm...surge suppressor, essentially.

The few sheets I found don't say anything about being radioactive, though one states "...three graphite electrodes mounted in a gas filled bulb...".

This would lead me to believe that either the graphite is part of a compound containing an alpha source, or it emits x-rays when actively suppressing surges.

If it does contain a source, the isotope should be printed on the box or glass envelope...if there is still printing visible. If that is the case, handle with care and see if you can determine the activity date. If it is an older alpha source, the gamma emissions would be more of a worry than the original ones!

I would keep that one away (time, distance and shielding) until you figure it out for sure.

I googled around about it when I first found it. The article stated that as long as I didn't break the glass I was safe. If the glass was broken not to allow any fragments of the glass or particulate matter from inside to get on your skin or in your body.

I am at work and the internet is restricted so I am having trouble finding more info (and finding the original document is impossible).

Drew K

The precaution may be due to Berillium. Berillium is used in the cathode material as an oxide (BeO) and is toxic. Probably not about radiation sources. If some of those tubes are rectifiers, then they may contain Mercury. Mercury vapor rectifiers are used for high power high frequency diodes.

So, if the glass is broken, be careful.

This site looks good. 6C8G @ The National Valve Museum

From the site:

"6C8G is a double triode. Each section has a separate cathode and the first valve has its grid taken to the top cap. This will confer greater isolation from the anode circuit than for valve two.

Intended for use in radio-gram type domestic equipment, the 6C8G provided audio amplification and phase splitter in one envelope. The final push-pull output stage was thus driven by this single valve.The classic envelope is 36 mm in diameter and, excluding the IO base pins, is 96 mm tall."

westinghouse electric ,defense & elec -- kx-642

Ingred Name:KRYPTON
Product ID:KX-642
MSDS Date:01/01/1985
FSC:5960
NIIN:00-501-0866
MSDS Number: BFBPP

The 6 indicates 6 volts for filament. IIRC 807's and 5Y3GT are interchangeble. They were used as amplifiers in HF transmitters. 6L6GC were also used as amplifiers. Seems as if you got an intercom system. Also try ARRL, they have a number of circuits that can be built.

You can probably sell them on EBay.

807 is a 5-pin tetrode transmitting tube good to 60MHz+, WW II vintage. Can be used as audio amplifier, a pair in class AB2 will deliver 120W at 750V plate volts. 6L6GC is an octal-based (8 pins) audio power amplifier tube, based on the 807, pair class AB will deliver about 50W at 400V plate. Can be used as transmitting tube to about 20MHz. Both tubes have filaments rated 6.3V 0.9A.

5Y3GT is a double diode power rectifier octal based. Filament 5V 2A, delivers about 125mA current, not enough for the amps above, but adequate for domestic radios.

For further specs, keep searching internet, hopefully to find RCA and Philips data sheets. Otherwise ask around the old radio hams for data books.

Are you sure about the 807 & 5Y3???? The 807 was used as an rf amp... In fact I learned about rf burns from one. The 5Y3 was a dual rectifier used in power supplies. I see no way that the two could be interchangeable.

Bill NW7L

I think that that radioactive symbol was at one time the trademark of Cal-Rad or California Radio. They marketed a wide range of radio parts. I don't think they actually manufactured anything. Those tubes are gold my friend. Voltage regulator tubes and varactor tubes can bring hundreds of dolls. The prettier they are the better. I made over $3k selling my collection of old tubes!

Anonymous Hero has a pretty cool power amplifier project, you might want to send him a message.

Of the ones you listed that I recognize they have 6.3 volt heater elements so just getting them to light up is rather easy.

All they need is ~6 volt AC power source.

You could sell the 6L6GC's for $75-$80, as they are a popular tetrode power tube in many modern tube amplifiers. My Mesa Boogie Dual Rectifier and Roadster use 4 each.

The vintage tubes are bringing the collector $$$

https://www.tubeworld.com/6l6gc.htm

The 6L6's are great tubes for audio amplification. They are popular, and I want them.

There are tube manuals on line that you can get the pin outs for these tubes. Simply use Google to search for them.

Applying the correct heater voltage to the tube will make it light up, but you need some current to do this and it will generate a good bit of heat. Do not bother to apply high voltage. It is dangerous and unnecessary.

A quick look at your list tells me that some of these tubes might be worth some money in the audiophile world. New-old stock of original tubes draws a premium price if they are good working tubes. So, it may not be a good idea to use them, but sell them to someone that can actually put them to use.

Many tubes are still made today either by original Russian/Soviet Block countries or China. Some are of excellent quality.

To actually make something from these tubes takes a lot of knowledge and work. I built a 50 Watt per channel power amp myself from scratch and now building a tube preamp to compliment it. The amount of effort and money it takes to do this (and do it right) is very high (more than the cost and effort to build a solid state amp), but for many of us it is a labor of love.

I figured this is what I would learn. I was hoping I could get them to light up a flashing sign or something without too much trouble.

They are all used, I pulled them out of the control panels of a power plant built in the 1930's. The radioactive one was in a box but shows signs of being used also. I doubt any of them are really worth much.

I need to check into some of the old hardware stores around here for a vacuum tube test bench.

Drew K

Even if you applied the 6v for the filament, the light would be rather dim.

At best a low red glow.

The filament is the only part of the tube that actually produces light (unless the tube is undergoing thermal runaway).

In some cases you may get a dull blue glow from residual ionized gases in the bottle or contamination on the inside of the bottle when the high voltage and cathode to anode currents are active. It depends on the tube. Some power tubes will do this.

Or unless the tube is a power tube where the plate functions also as a getter. In these you'll notice no silvery material on the inside of the envelope as you would normally in tubes using a conventional getter. You'll often see the plates in Eimac power tubes glow a dull to orange-red during normal operation. This is not an indication of thermal runaway; the high temps are necessary for the zirconium coated tantalum plate to capture stray gasses in the tube.

You can experiment, if you like, using an LED connected to the plate of one of those tubes which contain one or more grids/screens (even a pentode [like a Pentium, only cooler]), and modulate the LED's brightness by means of a negative voltage (with respect to the cathode/heater) impressed on the tube's grid (pick one). The juxtaposition of a vacuum tube and an LED makes for an interesting display.

The heater/filament in a vacuum tube boils-off electrons in normal operation. The effect, called thermionic emission, is enhanced when the element is treated with thorium oxide. In later vacuum tubes the filament is often seen inside a thin cylinder, called the cathode. This element is usually held at ground potential potential. If you do nothing, a cloud of electrons - called space charge - will form around the cathode even with no other voltages applied.

A positive voltage (with respect to the cathode. All voltages mentioned in this post are with respect to the cathode heretofore) is applied to the anode, often called the plate. It is usually a fairly high voltage in normal operation, often in the hundreds or sometimes even thousands of volts. The positive voltage attracts the electrons emitted by the cathode and the flow of those electrons from the cathode to the anode constitutes a current, one flowing through empty space.

When you interpose a screen-like structure between the two structures and impress on the screen a negative voltage, you can modulate this stream of electrons. With no voltage impressed, the electrons simply fly through the screen as if it weren't there (except where a tiny minority of electrons hit the wires, of course, causing a negative charge to build up on the screen. If you don't bleed off this charge, it will build to the point where the screen repels and further electrons and the current through the screen stops altogether. To prevent this from happening, tie the unused screens [if applicable] to the cathode).

In typical vacuum tube construction, the screen is quite often located physically much closer to the cathode than it is to the anode, with the result that a fairly low negative voltage on the screen will repel the electrons more effectively than the higher anode voltage can attract them. If the screen voltage is sufficiently negative, it will cut off the flow of electrons altogether (just like when negative charge builds up on the screen, except in this case you're in control).

The ability to vary the (possibly large) currents in vacuum tube by means of this screen voltage is the basis of the tube's ability to amplify. Vacuum tubes are still used, in fact, in very high-power radio transmitters and in some industrial applications. I recall seeing one tube in an Eimac catalog which was rated at 1.5 million watts. It was about the size of a small car. The screen - a water-cooled graphite structure - itself dissipated 20,000 watts. The screen. That was one kickass tube, lemme tell you!

Although a high voltage is typically applied to the anode in normal operation, this need not be so. Any positive voltage impressed on the anode will attract those electrons and so you're pretty free to pick and choose the voltage you apply to the anode in the case of your LED project. I used a 9-volt battery for the anode and a second battery used in conjunction with a potentiometer, wired as a variable voltage divider, for the screen. Because the smaller vacuum tubes typically conduct at most only a few milliamps, a dropping resistor in series with the LED is usually unnecessary.

This rig makes for an interesting science-fair project for your kid, btw. My son built one as his project one year. I can assure you he was the only kid in the entire country using a vacuum tube to demonstrate the flow of electrons through free space and how that flow could be modulated. Daddy, meanwhile, worked on a slightly larger variant of the same thing, except that his sent a 250 mA beam of 1 MeV phosphor ions hurtling through space and deep into spinning, water-cooled, 12" silicon wafers. I seem to recall seeing a couple of LEDs on it as well.

Which reminds me: Never, ever, ever shut a gate-type vaccum valve (not tube) across the beam in such a device when the beam is one. Why? Imagine, if you will, a slab of aluminum 'butter' thrust through with a large, white-hot poker. Yes, that fast.

If you snap off the plastic indexing plug at the base of the tube and expose the glass you can glue a colored LED and light the tube for a whole lot less current than the filament!

I respectfully defer to your proven expertise in this area, Sir. Will Gorilla Glue suffice? Please advise. :-))

I suggest looking up some of the Chinese audio sites. It is a very popular thing to do there.

Your point being...?

Wow...that sounds like a lot of fun. I think I would need a local mentor before attempting that sort of project. I do work at the power plant so I could get the power to run your butter cutter...but my safety guy would drop a brick if I told him what I was trying to do!

Drew K

Speaking of Russian vacuum tubes, I got a kick out of several I saw at Ham Radio swap meet: 'Hecho en USSR'.

Way back a long time ago, but after transistors had come into their own, one of NATO's simpler computers (such as it was) still used valves. It was finally decided that the machine should be replaced with something a bit more state-of-the-art when NATO Command learned that the sole source for replacement valves was located in East Germany.

Oops.

Btw, I've still got one of these. Never been used and still in the original horsehair packing and carton, dated April, 1958:

Eimac 450TH.

How much might mine be worth?

A really interesting tube I have never seen in real life. It is meant for radiative cooling. The last one of its kind I have seen in operation had thick graphite anode glowing yellow from the heat it was shedding.

Modern tubes up to a few kW are squat ceramic cylinders with a large metal heat exchanger meant for chimney + forced air cooling.

Much larger get water or boiling water cooling, to carry away really impressive kWatts in heat.

Thyratrons still see widespread use as high-current switches for use in high-power pulsed lasers. Also ignatrons, which do not contain a filament. The most common valves in service are klystrons used in television transmitters. The klystrons in the some of the very high power transmitters are as much as two storeys tall, come with their own vacuum pumps and can be disassembled for repair.

I've got a whole box of new tubes still in their boxes I picked up at an estate sale.

807s and 6L6 are still used by radio amateurs worldwide, that's for sure.

Advertise them and someone will put them to good use.

Flashing signs - I don't think so, they're not light bulbs. The filaments are 6.3 or 12.6 volts and take time to achieve full heat, which is often just a dull or cherry red and will be masked by the construction of the various other electrical plates inside the glass envelope.

I wasn't thinking of them flashing, just constructing a board that worked with a capacitor to switch on and off a sign or image.

In my gross inexperience with vacuum tubes I was thinking that they were replaced by transistors and through my gross inexperience with transistors I thought they were switches and I could set up a logic gate switch system to open and close circuits using the capacitor as a timer to make a sign flash...perhaps I should have started with this so I could have had my hopes dashed without learning so much about vacuum tubes...nah...I am enjoying learning what they are for too much!

Drew K

You can, but you need 100s of volts at the anode to make a switch.

Tubes (valves) work just like a solid state transistor except you need high voltage instead of 10 or 20 VDC. Valves also work the opposite of a transistor. A transistor is turned on by biasing the base or gate and a valve must be turned off by biasing the grid.

Testing for functionality - once you have the pinout - is fairly simple. It does not involve the frequently lethal high DC voltages.

I will describe the pentode, the most complex tube you likely to encounter.

It has a cathode, directly heated (the heater and emitter is one and the same), or indirectly heated (heater inside an insulated emitter). They glow dull red in operation. They tolerate +/- 5% deviation normally for heating. Cathode normally considered ground. A DC power supply is fine for heating.

The control grid is the first one. Normal operating range is -10V - 0V, no current.

The next is the screen grid. It is kept at the anode DC. Few mA current.

The next is the suppressor grid. Tied to the cathode or ground, it serves to separate the anode's AC swing in operation from the rest of the tube. No current.

The anode produces the amplified signal. By today's standard it is relatively high impedance: 10 - 100kOhm, for AC signals.

So testing is simple:

1,. One 0 - 20V DC, few Amps for heater / cathode. Do not ever overheat. Short term underheat is harmless. A few hours with heat only may mess up emission.

2,. One -20VDC - 0VDC 0 - few mA for control grid

3,. One +20 or +40VDC fixed, 100mA for second grid and anode.

With this you can fully test the tubes, except full output power. That would need (many) hundreds of Volts. No need for sockets, this is not a Radio Frequency setup.

Diodes, triodes, tetrodes work well in the same setup.

I mention this, because tube testers for older sockets at least, are rarer than the hen's teeth.

It's not good for the cathode filament to be on for long without high voltage on the pin connected to the getter. It will cause outgassing of the getter and poison the tube or at least break the vacuum.

Don't use these as lamps! Sell them before you break them.

Getter ??

The Getter is a piece of titanium which, when a high positive voltage is applied will "get" the stray gasses from the tube and maintain the vacuum. It is usually the metal ring you see at the top of the tube. Typically the glass above it is darkened and metalic looking. It is usually connected to the anode of the tube and makes use of the high voltage from there. In short, it is an electrostatic vacuum pump.

During final assembly, the tube is evacuated by a pump through the glass tubing in the center of the base of the tube. That tubing is then heated while still connected to the pump and the glass is pinched off. Then the whole tube is heated up and with all the pins except the anode/getter connected to ground, the anode/getter is juiced to 30-50KV positive. Any gasses that remained on the surfaces of the parts inside the tube are collected in the atomic matrix of the titanium in the Getter. Some of that material condenses on the glass and that is what forms the discoloration as the tube is brought down in temp and the getter voltage is removed.

Now, when the cathode heats up and heats the surrounding grids and anode, there will be no excess gas produced from the surfaces to spoil the vacuum. The getter will continue to maintain the vacuum over time AS LONG AS IT HAS HIGH POSITIVE VOLTAGE APPLIED. Without that, the getter becomes an emitter of gas as it heats up! That out-gas can poison the cathode material and the vacuum and destroy the tube.

An excellent explanation. Many thanks.

Barium and magnesium are more commonly used as getters. They are flashed by induction heating after the tube is assembled and form a mirror on the inside of the glass surface. The Russians use a titanium slug welded to the plate assembly, because they have lots of the stuff, and make pinch-bars and other tools from it (stronger than steel and half the weight).

Getters are not used in bigger transmitting tubes. Glass is cleaned with such things as chromic acid and distilled water. Tube elements are passed thru a hydrogen furnace to get rid of oxygen and surface tarnish. The assembled tubes are pumped and the electrodes heated to red-yellow heat to get rid of gas. Modern turbo pumps (high speed multistage fan turbines, 12000 rpm), together with a good backing pump, can go to 10e-8 torr or better, and are fast.

See books by Walter H Kohl.

This answers a question I had been kicking around. I recall reading about hydrogen and helium gas tend to escape any container because of the small molecule size. This made me think how could a vacuum hold with atmospheric helium and hydrogen on the outside.

Drew K

MY brother inherited my Grandfather's GE Tube Test Equimpent from his old TV/Radio repair shop. There were 5 x 35 gallon waste bins worth of tubes that were discarded when the shop was cleaned out. I am not sure if they are compatible tubes, but if you are interested, I can check with my brother to see if he would part with the testers.

back in the day, as I recall the testers are in wooden boxes, about the size of a phonograph, with numerous tube sockets, several rotary switches and a rectangular chronograph meter.

I have one of those plus around a hundred or so of the tube test cards that go with it!

It is a nice surprise, that somebody else remembers details of the radio tubes.

By the way, if the getter is all metallic shiny, the vacuum is good. When the edge, or the whole is milky, the tube is good only for its beauty, as the vacuum is already gone. I seem to recall, that the getter is Barium (from the Na, Ka, Ca, Ba series) in a metallic (Titanium?) capsule, that burst, when the whole thing is activated.

Barium, Magnesium etc. were also used, depending on the materials used in the rest of the tube and what gasses were expected. In any case, heating it up without high voltage on it is a no no.

We used (many years ago) titanium in a separate unit connected piggyback to the final pinch-off tube during the final testing and burn-in phase of production and then pinched them off the tube and re-cycled them.

The glass tubes in low power devices used them internally, and for those devices where halogens and oxygen were the gasses expected, barium and magnesium were used instead of titanium. Titanium could absorb anything, including H2 and Helium, whereas the Barium and Magnesium getters were reactive getters that bound chemically into componds that were stable at high temperatures in a vacuum. In some tubes, oxide layers were created to give a dielectric coating to the metal parts, and those would out-gas O2 on first use until they stabilized. Baruim and Magnesium are more appropriate for those kinds of construction.

All those old vacuum tubes are worth money for audiophiles who say vacuum tube amplifiers are still better than solid state amps. They are making a comeback, so don't destroy them. Many guitar amps still use vacuum tubes. The 6L6's are especially valuable.

They are making a comeback because they don't clip like solid state does. They just get fuzzier and distort at the peak of amplification. To a guitarist or audiophile this is a much better thing.

I processed the digital audio for two radio stations. My job was to normalize the tracks ripped from the CDs and locate excessive peaks that prevented the normalization routines from bringing up the volume levels on the majority of the track. Some had clipped peaks on only one cycle in the wave form lasting only a millisecond. The ear can easily hear that one tiny flaw! So when tubes are used in live audio instead of solid state, those moments of heavy handed plucking and drumming don't just cut off flat at the top. The quality of the audio in the performance is noticeably smoother and fuller and richer. Analog and tubes man!

These tubes are a gold mine! I did some research (Google NOS vacuum tubes) and found RCA 6L6GC matched pairs selling for $400

It all depends on where you shop and what you want I guess.

Around $17 each here or 4 matched around $100.

http://www.tubesandmore.com

As far as the fair market value of used untested tubes go a quick eBay search will bring the $$ signs out of your eyes right quick.

I have an old Electronamic Tube and Set Tester that is built in a wooden box. I also have several hundred tubes in boxes that I have never had a chance to research. And several tube amplifiers from old organs. They have been gathering dust around here for years. Good luck with your tubes