radio transmitter tube

[John]

Picked this up at the Arcadia hamfest yesterday just because it looks so cool. The Wife was so proud.    Anyway, the ceramic base says radio transmitting. Hoping someone can tell me a little something about it, just out of curiosity.

[PRR]

No numbers on the glass??

The "ceramic base" is just a socket, a very common type, though almost never found in consumer gear until the audiophiles rediscovered the 300B a few decades back.

[John]

The "ceramic base" is just a socket,

Well yeah, I did figure that much out.   


Actually, I should have followed up sooner, but here's what I found on Radio Museum. It's a Eimac 100T, btw.  And I got a funny feeling had you known the numbers, you'd have been able to tell me most of this right off the top of your head!


<quoted from radiomuseum.org website>

The company's first products were transmitting vacuum tubes which operated at low voltages, a design feature driven by the needs of the Ham radio community.

Bill Eitel, W6UF and Jack McCullough, W6CHE who founded the Eitel-McCullough, Inc. (most probably in 1934). Before they did the engineering work at Heintz & Kaufman in the early thirties for the HK354 tube which was designed to compete and surpass the RCA 852 tube.

During the development of the HK354 at H & K they had realized that the ideal transmitting tube of that time should be an extremely "hard" tube with a thoriated tungsten filament, Nonex glass bulb, cylindrical elements supported by the bulb with no internal ceramic insulators which could be a source of arc-over and plate and grid made of tantalum which could be made almost entirely free of gas so the tube need not have a "getter". The 150T was first advertised in QST in 1934 and was exhibited at the ARRL Convention 1934 in Sacramento. After that the tube was produced in series.

Shortly after the 150T followed the 50T, 300T and 500T, latet in the 30ies followed the 35T, 100T, 1500T and 2000T. The number was the plate dissipation a tube was made for. If a tube tested hat far ecxceeded the original ratings, they were numbered higher: 50T = 100T, 150T = 250T, 300T = 450T, 500T = 750T but the 35T, 100T and 2000T retained their original numbers and ratings.

Redesign in the late thirties and early forties were filament and grid structures, the open ended plate structures were given a domed top so that a single large plate lead instead of three separate leads as in the older design exits the top of the bulb. The internal glass ring, three wire grid support structure was changed to a simpler "press" design which made the tube easier to build. All this served to strengthen the tube and improve reliability.

Later these higher amplification factor types were to be labeled "TH's" and the older original lower amplification factor types were labeled as "TL's". Thus the 35T, 100T, 250T, 450T and the 750T became the 35TL, 100TL, 250TL, 450TL and 750TL.

During the late 30ies and early 40ies some other tubes were made like the 75T, 152T, 304T etc. and the UHF types UH35, UH50, UH51 and the Twin Triode were developed as well as tubes for the WW2.
Under the leadership of the founders, Bill Eitel and Jack McCullough, the company grew and expanded to meet the needs of the U.S. military, so that by 1945 it was shipping 3,500 tubes per day from two manufacturing plants. Following the end of the war, the company refocused on the commercial broadcast industry and developed new tubes for that application. Regarded as a technical innovator in the design of gridded power tubes, Eimac became the worldwide leader in the broadcast tube industry (Text published by CPI).

Officially one can read: "Since 1965 Eitel-McCullough (Eimac) has been merged with Varian Associates and became known as the Eimac Division." But the true story is that the much smaller Varian bought Eimac - but was wise enough to keep the name Eimac (info Mr. Ackeret).

In 1995, Leonard Green & Partners purchased the entire Electron Devices Business from Varian and formed Communications & Power Industries, Inc. This new company, with sales of $250 million, consists of the Beverly Microwave Division, Satcom Division, Microwave Power Products Division, Communications and Medical Products Division (located in Canada), and the Eimac Division.

[sluckey]

I'm curious about the socket and tube base. It appears to be a bayonet type socket (twist to lock). Could you remove the tube and take some pics of the empty socket and the tube base?

[John]

Sure thing, I will when I go home tonight. And yes, it does twist to lock. There are 4 pins on the bottom of the tube, that go into sockets that are sort of like the sockets on florescent fixtures. So as the tube locks with the little tip on the side, the pins also lock in the sockets.

[John]

Pics

[sluckey]

Thanks for the pics. Now I understand. I've seen a variety of tube sockets but never seen a socket like that before.

[John]

Shockingly      neither have I.

[PRR]

> never seen a socket like that before.

I *think* it works the same as a WE 300B.

The twist gives a serious wipe to the contacts when you put it in.

I suspect this is a heavy-duty revision of the old-old 4-pin base which goes back to the '01. That was stick-in, like Octal, and we know the tiny contacts are consumer-grade at best. The stuff, turn, lock design is more appropriate for high-value and critical operations (big theater, broadcast, and military).
__________________________________

> Eimac 100T

I did not know that.

However it was in my head that it might be kin to such tubes. I particularly remember a "4 plate" tube which was really four 75W(?) tubes built in one bottle for a 300W(?) rating. This is older and less tightly designed though.

If you know the type, wire up the filament and use it for a night-light. You can even use an AT (not ATX) PC power supply.

If you can find a mate, and PS and OT, you can get 400+ Watts out of the pair. (The driver would be a couple 6L6 or hard-worked 6V6 with a 10KCT:10KCT interstage transformer.)

The curves given are not conventional for audio amplifiers. I think I see a SE condition like 2,000V, 50mA, 100K load, and 20-30 Watts output. The higher powers will need 30mA peak grid current, but a 6V6 will cover that. Grid must be swung +60V to -300V. It's pretty crazy. Especially since you don't know if the tube still works.

[John]

If you know the type, wire up the filament and use it for a night-light. You can even use an AT (not ATX) PC power supply.

I don't know the type. The fella I got it from did say some of them make neat night lights though.


I doubt the tube still works since I got it for $15, and also since he said "uh, are you just getting this for display?". 

[PRR]

> I don't know the type

You said: It's a Eimac 100T, btw.

Look it up.  http://www.mif.pg.gda.pl/homepages/frank/vs.html

(As your note says, they re-named these tubes later. But they all have the same filament rating.)

Measure the Ohms of the filament. If it is "essentially zero", it will light. (If onfinity, like no-connection, it's a dud.)

It eats 5 Volts at a bunch of Amps. However well within the ability of a PC power supply. An ATX supply turns-on with a jumper. Poke one of the 4-pin drive connectors. Two center are COM, one side is +5V. Be sure you get the 5V, the other is 12V! Snip those wires at the connector, solder to the socket filament terminals.

[John]

wow. Plate voltages of 1500 - 3000.


I do have PC power supplies laying around that I'll take a gander at. It would indeed, make a cool nightlight! Datasheet says 6 amps. I might even scare up an old wooden box to house the PS in. Still need the fan for cooling though.

[sluckey]

I just used a simple mahogany block to mount some tubes on for display. The little one on the left is actually wired to a 6.3V transformer that sits under my desk. It does make a cool "what's that" night light. Yours would look even cooler.