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Author Topic: Tube of the Week  (Read 45557 times)
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Patrick J. / KD5OEI
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« Reply #75 on: November 03, 2022, 01:07:09 AM »

How about the 2D21? Not much is said about these little Tetrode Thyratron control tubes, and I learned something new about them today.

The 2D21 has alternate numbers such as the 4G/280K from STC, CV797, and its rugged versions, the 5727 a.k.a 2D21W sporting a 720G maximum shock rating. Some uses are relay control and radar pulse modulators. They work well on 120VAC circuits.

HTR=6.3V/600mA
peak inverse voltage = 1300
forward voltage  = 650
peak current = 500mA
average current = 100mA
surge 0.1 second = 10A
ionization time = 0.5us
plate voltage drop = 8V

The interesting thing comes from a old book "Gas Discharge Tubes" - it's from the internet and I don't know who wrote it, but they included a cut-away view from Penta Labs.

Looking at a physical 2D21, you see the grey anode - but it's an enclosure, not the anode. The anode is inside it. (page 67, figure 40)
The second grid is not a screen grid, but G2 is called the shield grid. It runs at -10 to -100V relative to the cathode.
The internal elements are fairly rugged, with G1 being the main example.

The 2D21 remains available in large quantities for low cost and could be considered an electically rugged alternative to some solid state switches.









* 2D21 cutaway view.png (97.21 KB, 810x1028 - viewed 248 times.)
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« Reply #76 on: November 03, 2022, 08:15:55 AM »

Hi Patrick,

   I once witnessed a 2D21 save a mans life!

Back in 1981 I took a job at the former Accelerators, Inc in Austin Texas. They had become a division of Veeco, and existed till 1987.

The chief Physicist, Joe Cecil, W5RIQ (SK) had an ion beam test stand that would accelerate an ion beam up to 120 Kev (ev = electron volts).

One day, there was Joe standing there with his arms outstretched on the beamline, and I witnessed a series of arcs, about 2 per second striking his hand.

It happened so fast, and before I could take action, the arcing stopped, and Joe lowered his arms, and without expression, he walked away! He was as white as a ghost!

He later explained to me, that the big 0-150KV Hippotronics supply had an arc fault circuit where it would shut down the supply after a fixed number of arcs.

The control element in that circuit was a 2D21!!

Jim
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« Reply #77 on: November 03, 2022, 08:47:22 AM »

"ENCLOSED ANODE TUBE SAVES LIFE!"   Great story and whatta strong tube!  TNX Steve
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« Reply #78 on: November 04, 2022, 10:02:38 PM »

I remember some early West Coast handbook circuits where a 2D21 was used as a 9 Volt regulator.  Filament voltage may not have been used, sorry just can't remember.
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« Reply #79 on: November 06, 2022, 06:36:33 PM »

Talk about safety circuits! It's even more interesting a tube after reading that.

The regulator circuit is in the 14th, 15th, and 16th ed. It's started through a high-R resistor to low B+ supply and serves as series-connected cathode bias for the 811s, instead of the Zener diode which did not exist at the time.
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« Reply #80 on: February 19, 2023, 02:04:23 AM »

Here's how the 2D21 really works.


* inside-the-2D21.gif (1815.28 KB, 480x270 - viewed 211 times.)
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« Reply #81 on: February 19, 2023, 02:06:54 AM »

There's nothing like an octal-based Death Star...
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« Reply #82 on: February 19, 2023, 02:21:11 AM »

The 1A3 is an overlooked yet interesting tube. The 7 pin miniature diode is good to 1GHz, has a plate-cathode capacitance of 0.4pF (unshielded),  and starts conducting at a very low voltage compared to many other vacuum diodes and all semiconductor diodes, according to the curves. The structure inside is tiny, perhaps contributing to this characteristic.
image page:
https://www.radiomuseum.org/tubes/tube_1a3.html

data:
https://frank.pocnet.net/sheets/127/1/1A3.pdf
https://frank.pocnet.net/sheets/049/1/1A3.pdf

There's plenty of hubub about linear detectors and rightly so, assuming the signal quality is good enough to warrant improved fidelity it might offer for the AM detection.

It's intended for FM discriminators. Other possible uses?
-An electrical replacement for the unobtanium vacuum diode found inside the RF probes on certain beloved old H/P VTVMs.
-A better detector for tube type audio compressors, on audiophool grounds anyway.

I have not tried this diode, but it's cheap at $2-3, or 75 cents in quantity 10 at https://vacuumtubes.net/Quantity%20Specials/Quantity%20special%20102.htm though this is a snapshot reference and not an avertisement.

If I run into a free one I will try the Vf experiment and report back.



* 1A3 diode curve RCA 1943.png (72.09 KB, 892x540 - viewed 179 times.)
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« Reply #83 on: March 17, 2023, 06:46:58 PM »

The 6V6G-E

Yesterday while helping with the radio-electronics parts of an SK estate while one of the daughters and the 11 year old grandson were there, I came across many 6V6GT tubes, some 6V6Gs, and two or maybe three 6V6G-E tubes, which seem to look just like the 6V6G. These is one apparently sealed and old box that said 6V6G-E on it, but I was in a hurry and dazzled by all the hundreds of tubes I was looking through and don't recall.

Has anyone else run across a 6V6G-E ? I will try to get pics of one and the box tomorrow, depends on schedule.

For this reason of apparent oddity, I submit the 6V6 in all incarnations as a Tube of the Week.
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« Reply #84 on: June 11, 2023, 09:58:27 PM »

How about the HK 354C Gammatron?

The HK354C is one of two 354 types, each with a different mu:
C = 14
E = 35

It's a healthy 3" diameter, and about 8" tall. The plate is Tantalum, and the Tantalum grid is of braced vertical bar construction.

Some 'max' data from the 1936 data:
Plate Voltage = 4KV
"Average" Plate dissipation = 150W
Plate current = 0.3A
grid current = 0.05A
Average Plate Impedance = 2800 Ohms
Filament 5V @ 10A Thoriated Tungsten.
Plate shows barely at 75W, a dull red color at 100W, and a medium red color at 150W dissipation.

Class C plate modulated amp output (100% modulated peak): 630W @ 3KV
Class B linear amplifier output (carrier level): 82W @3KV
Class C Telegraphy RF output: 840W @ 4KV.
Class B Modulator output (two tubes): 665W @ 3KV

All this said, it takes higher drive voltage compared to more modern tubes, but not so much that's it's impractical. The drive power is no more than 50W for CW in class C, and just 10W peak for the class B linear mode.

https://frank.pocnet.net/sheets/114/h/HK354C.pdf

https://frank.pocnet.net/sheets/114/h/HK354.pdf

Found one NIB unused -the images -, though its original box and packing is disintegrating after all the years. It's a really beautiful and well-made old tube and a real pity that it's more or less unobtanium. Looks like it's pretty much a museum piece.


* HK_354C_Gammatron NIB_0.jpg (76.12 KB, 1000x709 - viewed 132 times.)

* HK_354C_Gammatron NIB_1.jpg (203.64 KB, 1780x882 - viewed 143 times.)
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« Reply #85 on: June 11, 2023, 10:10:46 PM »

Updating the previous 866Jr post:

https://amfone.net/Amforum/index.php?topic=46518.msg337822#msg337822

Found a couple of the Taylor units today and here's a good picture of them. Different year of manufacture looks like.
Sorry that can't be ON and glowing!


* Taylor 866Jr tube image.jpg (222.97 KB, 1500x1686 - viewed 144 times.)
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« Reply #86 on: July 02, 2023, 06:54:16 PM »

Today, I present the 0G3, also known as the 85A2.

This 85-Volt gas regulator tube is not as common as other 7-pin regulators, but it's a more precise tube than the usual higher-current 0A2-sized tubes, and used in various test gear as a reference. Advantages are a more stable and constant voltage over the life of the tube, which helps gear stay calibrated. The usual operating current in the 0G3 is 1 to 6mA.

The H/P 400D/H/L series of VTVMs use the 5651 regulator, but I have one with an 0G3 in it and it seems no less accurate for the substitution.

The image is of 21 of them placed in series in a phenolic? box. (cover present but removed) Anyone recognize this assembly?


* 21 0G3 tubes in series_small-2.jpg (197.58 KB, 1200x545 - viewed 138 times.)
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« Reply #87 on: July 12, 2023, 12:45:29 AM »

This week, lets look at the 6012 Shield Grid Xenon Thyratron. It's a big brother of the 2D21 and 2050. It's about the shape of a 6146 sans cap, maybe a bit taller than the 6146.

Looking at it, you can tell it's not the average tube. The large rectangular anode fills the glass from side to side, beckoning to megalomaniacs.

Some data:
Heater 6.3V +/-10% @ 2.6A
Forward Plate voltage: 650 (non-conducting)
Reverse plate voltage: 1000 (1300 peak on AC)
Peak plate current: 5A
Average plate current 500mA

One application is as a motor drive, very nice indeed. Otherwise, used as a relay and grid-controlled regulator.



* IMG_20230530_123215118small.jpg (105.45 KB, 1200x1058 - viewed 141 times.)
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« Reply #88 on: July 20, 2023, 12:30:07 AM »

How about the 4B31 ?

The 4B31 (RK-4B31) is not a typical 'cheaply had' tube, nor one that is seen frequently. Nonetheless, I got one for free in the W5FRS estate and it's interesting to consider for at least one analog AM application, so it's worth a place here.

They are at first glance costly to buy at $12 to $60, but it's a high-value tube when comparing ratings per dollar, so it's really dirt cheap plentiful because the audio folks don't like them for some unknown reason!

4B31 is the same tube as:
RK-4B31
CV3510
QK98

The Raytheon 4B31 is designated as a clipper diode and rectifier. It's ruggedized, exhausted at high temperature to a higher vacuum than many rectifiers, and has a 'hard glass' Nonex envelope. The plate is Gold plated and Zirconium Molybedenum coated. The cathode is heliarc-welded. The spacers are ceramic. Looking closely, it appears to have two cathode structures acting in parallel.

Considering it as a clipper for purposes of negative peak limiting/keep-alive or 'ultramodulation', it could be compared to the 8020 vacuum rectifier, both easily handling the usual ham radio plate modulation voltages and currents. There is no mention of the 4B31's plate dissipation but it's a big plate there.

(There have been many neg peak limiter/keep alive/supermodulation setups with Mercury rectifiers (as famously shown in a video with  Ashtabula Bill), and also many with semiconductor devices, but I want to split hairs here and highlight the smooth vacuum rectifier characteristic)

4B31 basics:

Absolute Maximum as Clipper Diode:
Filament voltage: 5V@5A
Heating time: 2 minutes
Cathode: indirectly heated
Peak inverse voltage: 16KV
Peak plate current: 12A
Average plate current: 60mA

Absolute Maximum as Rectifier:
Peak plate current: 470mA
Average plate current: 150mA

Characteristics /Typical Operation:
Plate current @130VDC: 300mA
Peak emission @2500V: 18A

The average resistance of the tube is 400-300 Ohms over a forward voltage of 40 to 150V (The 8020 has a resistance of about 1000 Ohms).

I don't know what to make of "The plate is Gold plated and Zirconium Molybedenum coated.". There is a gold appearing area on the plate but I can't tell if it extends to the inside of the plate, and don't understand the use of 'zirconium-molybdenum'. There are plenty of pictures of this type on the internet to examine.
https://www.google.com/search?q=4B31+tube&tbm=isch

Datasheet: https://frank.pocnet.net/sheets/138/4/4B31.pdf

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« Reply #89 on: November 07, 2023, 02:43:24 PM »

Enough of these Thryratrons! veterans’ day is coming up so what about a good military only tube? The PL-177WA, that was the final amplifier in the AN/PRC-47 and think as far as I know wan never used in anything else. The PRC-47 was somehow considered a field radio although it required a crew of at least two to three people, usually Marines being the Army had better radios like the PRC-70 or PRC-74 so they did not have to lug that mess around.
The PL177WA provided 100 watts of USB from 2 to 12 MHz with 1,500 volts on the plate in high power and 650 volts in low power, although every PRC-47 I have ever owned would do maybe half that.
Another good contender would be the 4CX350F that’s the military version of the 4CX350 except it has a 24-volt filament and is used in radios like the AN/GRC-106 and the Collins 618T transceivers. May be mistaken but think they were stuffed up the AN/URC-32 also.

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