Tube Reactivation: Receiving & Transmitting

The '71 tube was reported to originally been a thoriated filament...

The oxide number became '71a...

The 210, may have an oxide filament or a thoriated. Observing the filament color with correct voltage, thoriated will be medium orange to a yellow. The oxide will be the customary "toaster" red/orange...

There is at least one Deforest tube that is thoriated, can't recall the type number.

Chas

Anybody seen my

Correction on release of the UX-112 output tubes:
I have confirmed that the initial release of the RCA Radiotron UX-112 tubes did have 5V at 0.5 Amp oxide coated tape filaments. This information came from a first edition Radiotron data sheet dated August 1, 1925. The UX-112-A tubes that followed had 5V 0.25A oxide coated tape filaments. This change would have reduced battery drain. Presumably they met the same specs as the UX-112 tubes. There may have been variations among the many independent tube manufacturers.
73, Rod  WB6FBF

When I was teaching myself about DC, batteries & magnetism, home made Morse sounder. I could not get my Dad to go for a couple of number six cells. They were 75 cents at the time, a little later $1.25...

So in my neighborhood exploits on bicycle I past the Town Yard. The Department of public works used a lot of war surplus waterproof lanterns. What caught my eye from a distance was a large pile of cylindrical objects and what looked like tar. Well tar is tar but the round objects? There was much more trust in the world back then there was no gate on a Saturday afternoon so I went exploring the "pile" It turned out the pile was number six cells. Instead of them going to the dump, for what ever reason, there were deposited in this heap. On top were the latest ones, too "dead" for lights, but having read the Boys Book on Electricity, I new I could get a few more watts out of them. I took home, some 6 cells. Rummaging through the heap there were a bonanza of Fannestock clips and battery nuts, by the trouser pocket full Oh the tar? batteries that had been there a couple of years had burst open carbon dust. I did salvage a few carbon rods but I was never into making an arc lamp or an electrolytic detector. I did not fool with any acid or alkali stronger than lemon juice and baking soda...

So I got a couple of large canning jars from Mom and placed a cell in each after I had punched holes in them with a nail, then added some tap water. Ta DAH I got power! Enough to light a 300ma bulb. So I series up several and got 6 volts for my Morse sounder...  New toy for a couple of weeks but the cells were giving up. Now the next lesson, I thought that if I could hook the cells in parallel I could get a few more watts. Opps I confused (+) and (-) I accidentally created a short circuit, but I did not notice. I looked the next day to do my test and the mason jars were all muddy and tops of the batteries frothy. Stone dead, they gave their last to teach me about polarity... Glad it was my salvage cells. Dad would have been very angry had it been a pair of new store bought cells...

A tip from my Dad: Your "B" battery totally dead? Get one last use out of it. When the fireplace is going good, toss the battery on the fire, get pretty colors and the chemicals will help clean the chimney... (no one was thinking lead back then)

Chas

Frank,
Adding some sal ammoniac (ammonium chloride) to the water would probably help some too. Revives the chemical content a bit. The carbon rod would still be good and there should be some zinc left too. When I was a boy I tried making my own carbon-zinc batteries for a while.
73, Rod

Another trick on A batteries I was told about was to drill small holes in them and inject some water into them. Never have tried it, but it was supposed to rejuv the chemicals. Don't know anything more about that though.

FrankB wrote:

One article I read decades ago
instructed you to place the tube in an oven and "cook it" at a certain temp for a specified number of hours, after rejuv.

O.T.

My Dad told me he would put [You must be registered and logged in to see this link.] cells and "B" battery blocks in the oven and get a couple more weeks out of them...

I have placed Zenith transoceanic chassis, the was literally dead to the world in the oven, after removing all the plastic and rubber parts...

Some end wax flowed out of the paper caps but firing up the T.O. it came to life with tremendous sensitivity.

Still have that radio, OEM caps and it still works:)

Overall, for the radio restorer there is a LOT that can be done with an oven, mast at temperatures below 212 and some jobs at 275 to 300F...

In modern SMD boards, heating the board facilitates removing of devices when they are soldered to a heat-sinking ground plane. In re-work heating the board actives solder paste to solder the new devices to the pads.

Heat can be used to flatten a distorted hard rubber radio panel. Also heat is used to melt bees wax and drive out moisture in coils using a vacuum chamber (simple really)...

After refurbishing a radio, I thought that wiping down the flat (foil embossed) loop antenna would be a good idea.  NOT! the water soaked into the Masonite hardboard and "killed" the antenna "Q". I agonized over this and thought the antenna/back was ruined...

Then it occurred to me to place the loop antenna back into a warm oven for a couple of hours. Yeppers! It worked, radio returned to normal operation...  

Chas

One article I read decades ago
instructed you to place the tube in an oven and "cook it" at a certain temp for a specified number of hours, after rejuv.

Thank you for your wonderful answer.
I have learned a whole new segment about old those tubes.

The mechanism of the thoriated filament involves the tungsten alloyed with thorium. The thorium also improves the drawing of the filament wire through dies to the needed size. Thorium increases the emission of the filament many, many fold and has to be but one atom layer thick to do so. However, those atoms are pulled off by abuse of the tube by exceeding the electrical bond between the layer and the wire itself.. Additional thorium ions are below the surface and will not migrate to the surface until the temperature of the filament reaches that of an operating tungsten filament. Literally, boiling the thorium to the surface. The thorium now on the filament surface and highly excited can easily be pulled away and never to return if any positive potential is on other elements. So important not to have any connections to the grid or plate.

Yes many, many folks have used substitute tubes. What happens is this:

- In generally 20's era sets are not designed for any shielding nor consideration for placement of input/output circuits. They work simply because there is very little gain in the tube and in any I/O passive devices, like RF coils and audio transformers.

- Almost all substitute tubes will have higher gain, therefore, the circuits may go into oscillation.

- Almost all substitute tubes will have a different filament characteristics, of which the original tubes relies on the voltage drop in the filament rheostat to develop part, if not all of its bias. A substitute tube of will not be compatible with the radios rheostats.

Most 20's era radio can have cross substitutes like a WD-11 gets a '99. A '99 can be subbed by a '01a with changes to rheostats and "A" voltage. They are all low gain tubes. There were socket adapters to do this.

All most any tube can be subbed into a one tube regenerative radio later tubes may experience sensitive regeneration of lack of filament control but using shunts on the filament it will work.

A direct substitute for the WD-11 is the 864 with a base adapter, no "A" voltage change. I have used the 864 on a Radiola III with great results.

Transmitter tubes with thoriated filaments are treated differently. No flashing, just an elevated filament voltage, no other element connections.

One would have to consulate the manufactures recommendations for such a procedure.

The 210, 203, 204, 833 I am aware, are thoriated as well as a modern tube used in ham transmitters. One recommendation is also to burn the thoriated transmitting tube for a day if the tube has been idle for a long period of time. This is to activate getter, gas in a transmitting tube can be fatal by causing an arc over. The arc creating a hot spot on the filament and burning it open.

I began re-activating tubes in 65-66 after receiving a large radio collection in '63 with bushel baskets of tubes. Getting some of the sets to work required testing and rejuvenation. I was fortunate to have several 20's era hand books that also had the information.. Somewhere, I have a photocopy of the US gov. bulletin on tube re-activation. No one had a treatise on rejuvenation and the charts varied in "precise" figures. So I chose average figures for voltage and time.

Discovering that the best and least wasteful process was to simply burn the tube at slightly elevated voltage, if good stop. If not raise the filament voltage for 15 minutes, again, if good, stop. If not, full flash voltage and procedure including aging.

All knowing that the full flash procedure has a limited number of times that it can be performed with success...

I can say some '01a's will go open during the process. Some will be found to have gas. The old handbooks recommend that any tube found to have gas be saved for the detector. The gas being an advantage in the grid leak circuit. Other "hard" tubes reserved for the RF and AF amp where distortion from gas would be noticed.

GL to anyone trying the process...

I used to do rejuvenation on a Triplett tube tester, I made a jig socket, used with a v99 adapter and a filament only interposer for rejuvenation. All timing was manual and the filament voltage monitored at the socket.

I have two different brands of 20's era rejeuvenators, one I recall, is a Jefferson, the other I have forgotten, but that one includes a plate current meter...

The '99 is a pricey tube even used untested but if found in lots untested there is a chance to get a bargain by rejuvenating. OTH '01a's untested can be as low as $2.00 so bargains are out there. Between re-soldering the base pins and rejuvenating the filaments good tubes can be saved to serve again after nearly 100 years...

Oh, High voltage and tube rejuvenation?

Nope However! I have used a Ford coil to find where breaks are in tubes that tested open even after re-soldering the base. I had suspected the base soldering failed when tinning the wire lead did not seem effective. Most 201'a are highly silvered and it is near impossible to see inside if the filament is not working. The harmless arc of the Ford coil shows where breaks are in the filament. I did this to determine if I wanted to remove the tube base for further repair.

One part of this "tube saving topic" not covered is dropped tubes that are shorted.

Sometimes, an "S bulb tube is dropped and does not break but the elements are off to one side and shorting. This sometimes can be fixed... Remove any rings from the hand that will receive the "smack" of the tube bulb. Place cotton gloves on both hands and wear eye protection.

The trick is to use the stored inertia in the rapid movement of the tube in one hand and have it stop abruptly in the palm the other hand. Hold the tube in the hand that will move and orient the elements that are bent in the opposite direction of the intended movement. Starting about 18" away from the hand that receives the bulb of the tube in the gloved palm, accelerate the tube and stop it in the receiving palm. Do this all while holding the tube. Do not throw the tube. Check the elements to see if they have returned to correct position. Sometimes the bend has to overshoot by bending the plate to far only go back as the grid may not bend as much.

I have done this several times and always succeeded in repairing the tube.

Some have even experimented at "welding" an open filament. I have not experimented in that area but have tapped a filament to work with but partial success for a short while.

Chas

Are there any modern Tube substitutes? Or adapt circuits to accommodate?
I understand the argument of keeping things original. But if the tubes are beyond redemption why just let the radios be self queens collecting dust? I would think A modified radio is better listening than a silent one. J MHO

Another thought is mentioned in the referenced article about not being evacuated properly so why not try a high voltage on the plate and small disk on the outside of the glass to the getter area if it has one.
May attract those molecules to the getter?

Cliff,
The subject of tube reactivation of "weak" and "dead" Thoriated Tungsten filament type tubes has been one of interest for many years now. As Chas mentioned, it started back in the 1920s with the first of such tubes made and released for sale. It can apply to transmitting as well as receiving type tubes. For tube and radio collectors focusing on the 1920s era the earliest made receiving tubes like the UX-201-A are the most fun to test, use, and try to reactivate if needed. Some types, as mentioned in the referenced article Chas gave (suggested reading), note that tubes that use tape or ribbon type filaments and are oxide coated (that white coating you see on the filaments and sometimes particles of it are floating around loose in a tube) are generally not suited for reactivation *. These would include the 1920s "Power" output types 112-A, 171-A; and the earlier WD-11, WD-12, WX-12 detector-amplifier types. Also included in the "Do Not Reactivate" group would be any tubes with pure tungsten filaments such as the original UV-200 and UV-201 tubes. No reactivation of these latter tubes are needed as the filaments are self cleaning and run at high enough temperatures to function (emission wise) adequately.

Here is a link to Lane S. Upton's December 1973 OTB article I referenced before as being a good source of information on how to go about doing tube reactivation:

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There is also another version of Upton's article on tube reactivation available on one of the antique radio websites. I forget if it is credited to Upton though.

* Upton presents some additional info on reactivating oxide coated filament and heater-cathode type tubes but I have yet to try out any of the methods presented in the article. For example: I would hate to damage a weak but usable 45 or 71A tube.

73, Rod  WB6FBF

P.S. Far as I know, the UX-112 and UX-171 tubes as originally released with 5V and 0.5A filaments were of the Thoriated Tungsten type. I have seen a few examples of such tubes. There may have been some variation from one manufacturer to another. Not long after, they were switched to the improved oxide coated ribbon filaments. As another example, I once had a sample of a tube (Vox) that was branded UX-201-A yet it had an oxide coated filament. It featured a single inverted "V" filament. It tested and performed about as well as a  112-A tube.

Totally unfamiliar with this topic.
Just an Idea. Have you tried using a very High voltage very Low current (like static electricity)?
On just the filament. Or between the filament and plate?
I don't think it would accomplish anything, but nothing ventured nothing gained. Try it on one you know you can't reactivate, as an experiment. Try different times of application recording each results. And varying the voltage as well.
Could be a waste of time but like Edison said I have found 1000 ways that don't work.
Just a whim on my part.

The process of activating thoriated filaments was published in the 20's when the tubes were introduced. Folks were not familiar with the tubes would under certain conditions, paralyze or essentially strip the thorium from the surface of the filament. The early 1 amp tubes folks would just crank up the filament voltage to get results. Some early sets did not make use of a "C" battery and operated the amp plates at 67-1/ 2 volts, that is O.K. but to get more volume the radio fan would kick it up to 90 volts. The excess plate current would strip the thorium. One radio manufacturer suggested that once a week the B battery be disconnected and the filaments burned at full brilliance for a 1/2 hour. That procedure does work but does waste thorium as the grid is still connected...

Many later battery sets are found with roasted filament rheostats, 1 amp tubes were installed, oops...

The procedure for tube rejuvenation that is stored on Nostalgia Air is nearly a direct copy from the 20's. Saves me from repeating it as I once did...

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I will stress, do not have any connection to the grid and the plate during filament re-activation, at elevated filament temperature any circuit will strip thorium as soon as it comes to the surface.

Some tubes that have been in use a long time will have filament etching, when the higher temperature (voltage) is used the filament may part.

When in doubt always remove old tin solder from the base pins and re-solder, scrape the element wire if practical. Always heatsink the pins or the Bakelite base will blister, the pin will get loose if that happens. Re-soldering reduces the voltage drop on the pins a common cause of a "weak" tube...
Type 99 is touch and go, the brass base 99 is 3 volts filament not 3.3 so a 10% reduction of rejuvenation voltage is in order. SongBird brand is often gassy, burn the filament at lower voltage for an hour or so then rejuvenate. Reduces the risk of burnout at rejuvenation voltage levels.

YMMV

Chas

I have tried reactivation of weak and "dead" 201-A type tubes starting some years ago and recently I have been at it again. It is an interesting field of study and experiment. I have Lane S. Upton's article (December 1973 OTB) to go by and it is a help. In the distant past, I had one of those Sterling tube reactivators. They are capable of "flashing" the filament and then running it at a lower filament voltage for "aging" purposes. Upton recommended going with flashing if the milder reactivation process didn't help much.

A couple of points to start with: 1. Tubes that have been idle (unused) for several decades may test "dead" initially but are capable of recovering rapidly and fully if run at normal filament voltage if only briefly. I have actually seen this happen when checking out a "new" 201-A type tube with my Hickok 540 and/or 550X testers. I would get no reading initially but later on would find it had partially to fully recovered its emission capability. 2. Some tubes will be particularly stubborn to reactivate. They may not respond much, if at all, to the mild reactivation process.

This was the case with an unknown make, unlicensed (probably made before May 1929) "UX-201-A" tube I recently bought and received. The filament was good, was not shorted internally but dead in all other respects. For a while, I actually thought that the grid and plate connections were open internally as the soldering of the leads to the pins were good. On this particular tube someone had resoldered the filament pins before so that was an indication that there had been a problem with the tube.

After following the recommended 135% filament Voltage reactivation method, I found some small improvement in the tube. It was now conducting a bit but not nearly well enough. At least it wasn't "open" any more hi, hi. I found that increasing the filament voltage, while under test, to 6.3V then 7.5V increased the test readings but the effect was mostly temporary. There was a small overall improvement with these increases in filament voltage though. When I finally ventured to try it on the 12.6V filament setting (for 10 seconds) I did get a very high test reading and a much better improvement back at the 5V level on the filament. I was now getting a 200+ uMhos reading with the Hickok 540. That was a big improvement from where the tube had started (as good as some "hard" tubes made before the release of the UV-201).

Next, I decided to try setting the filament to the "flashing" voltage level of 3.5 times 5V (17.5V) as given in Upton's article. I had been reluctant to do this before because of previous burnouts years ago when I had attempted it. Well, that is exactly what  happened. The tube's filament couldn't take it. I am thinking now that it might have been better to boost the filament voltage a volt at a time (from the 12.6V setting) up to about 15V, if necessary, but stopping when the tube's performance became good enough to use in a radio (or even as a rectifier in a tube tester). The usual 60-65% tube tester cutoff level of around 450 uMhos would be good. 

73, Rod  WB6FBF