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Tube of the Week




 
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« Reply #25 on: January 26, 2021, 10:32:15 PM »

Ed, sorry to 'steal your thunder'. I didn't know what was happening 'behind the scenes'. Everyone was talking about the TOTW and nobody proposing one. So I kind of took the bull by the horns so to speak. I will fall in line with the majority here.
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« Reply #26 on: January 27, 2021, 02:57:05 PM »

Ed, sorry to 'steal your thunder'. I didn't know what was happening 'behind the scenes'. Everyone was talking about the TOTW and nobody proposing one. So I kind of took the bull by the horns so to speak. I will fall in line with the majority here.

No issue, no thunder stolen, just a timing thing. You made a model post, hope mine are almost as good.

Ed
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« Reply #27 on: January 28, 2021, 11:19:48 AM »

Quote

Thanks, I needed that! Until Ed comes up with the tube of the DAY/WEEK/ I want to thank KY4SP for that information.

Terry
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« Reply #28 on: January 29, 2021, 11:24:15 AM »

Friday January 29, 2021 Tube of the Week:

This week's special is the 6CL6. Also numbered as JAN 6197, it is a 9 pin miniature style tube, a pentode. This tube was designed as a video amplifier for TV service. They are very available on eBay, for as low as $2, making them suitable for playing around with.

Datasheets, from Frank @ pocnet:
https://frank.pocnet.net/sheets/049/6/6CL6.pdf  This one has an amplifier circuit snippet with component values!
https://frank.pocnet.net/sheets/093/6/6CL6.pdf

When you look at this tube, some might think, "Boy, that looks a lot like the 6AG7" and you'd be right. The 6CL6 was the 9 pin miniature replacement for the octal 6AG7. Hams have been using the 6AG7 for many years as one-tube CW transmitters, oscillators in larger setups, and as the RF part of a simple phone transmitter (a notorious example, the Heil Pine Board). Well, The 6CL6 can do the same thing.  Another feature (or issue to be aware of) -- the suppressor grid is NOT tied to the cathode internally.  This could lead to its usefulness for experimenting with suppressor modulation, or use in circuit where you do not want the suppressor referenced to the cathode (like a series modulated setup, perhaps).

Some ideas and prior art:

AA8V: https://www.frostburg.edu/personal/latta/ee/6cl6xmtr/6cl6xmtr.html
WA5BDU:  http://pages.suddenlink.net/wa5bdu/2_tube.htm
AF4K (Incomplete/old page, unfortunately the owner is SK):  http://s88932719.onlinehome.us/2e26.htm
VK1SV (adding the 6CL6 to last week's Tube, the 807):  https://people.physics.anu.edu.au/~dxt103/valves/807/


So, there you have it, an interesting tube type, less common, inexpensive, and available.   Time to order a few, and start plotting out ways to see what you can do with them! If you move fast enough, you could get one on the air for next weekend's AM Rally!

As always, your comments are welcome. If you have a suggestion for a future Tube of the Week, please PM or email me.

Ed
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« Reply #29 on: January 29, 2021, 11:32:05 AM »

a great tube 6cl6 .... collins used them in S line as PA driver ... output very linear .... EFJ used them  (2) in the ranger I as class C Oscars / amp .... seemed to be long lived in that application .... when overdriving for class C  keep the grid resistance high (100K) to keep from cooking the control grid
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« Reply #30 on: January 29, 2021, 02:39:14 PM »

Before Ed gets started on his weekly favorites, I would like to mention that the 6AL7 has a very nice radiation pattern, as seen in the attachment. 

With the deflection of two rectangular bars and three deflection plates, it is able to indicate proper tuning, signal strength, and relative audio volume simultaneously!

And who needs a 6E5/6U5/1629?  Why settle for one when you can have two with the 6AF6?


* 6AL7pic.jpg (4.54 KB, 169x184 - viewed 197 times.)

* 6AL7pinout.JPG (18.26 KB, 279x239 - viewed 188 times.)

* 6AF6pic.jpg (8.33 KB, 267x269 - viewed 190 times.)
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« Reply #31 on: February 06, 2021, 01:48:42 PM »

Sorry, a day late. Tried to get ready for the Rally instead of typing..

So, in keeping with the idea of availability, interesting, and honor towards the guy with the idea (Opcom), here's this week's fire bottle:

6N7, an octal-based dual triode. Designed as a class B amplifier for push-pull circuits. One significant difference vs. other dual triodes like 6SN7, 12AX7, 12BH7, and so on, the tube has a common cathode for both sections.  Often seen as a metal tube, there's still some out there as WWII surplus.

Here's the data sheet:
https://frank.pocnet.net/sheets/049/6/6N7.pdf

So, with a tip of the hat to Patrick, who came up with the idea of fun tubes some time ago..here's the first reference:
http://amfone.net/Amforum/index.php?topic=30912.0

Some interesting circuits:
QRP linear:  https://www.glowbugs.info/2010/06/6n7-tube-qrp-power-amplifier-one-rainy.html
Lettine 240: https://bama.edebris.com/download/lettine/240/240.pdf
One tube, push pull: https://www.kb6nu.com/a-one-tube-push-pull-transmitter/
paralleled, doubler:http://jlandrigan.com/files/75Watt%20807%20triband%20with%20JEL%20end%20link%20coil.pdf
audiophool version: https://theaudiofeast.com/blog/finemet-fm-10p-14k-6n7-push-pull-class-b2-amplifier
early guitar: https://www.magnatoneamps.com/schematics/magnatone_M-195-4-J-1949.jpg

As you can see, it's versatile enough to be used for audio or RF, time to find a couple and play around!

As always, please comment and expound with your experience and knowledge. If you have a suggestion for a tube type or would like to write one up, please email me at the address here in the member section (or QRZ).

Ed









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« Reply #32 on: February 06, 2021, 01:54:20 PM »

Yep, it's predecessor is the 53. 

Can make 10 honest watts in PP cl "B".  Cheesy

A single with paralleled elements makes the ideal driver for said PP amp.

73DG
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« Reply #33 on: February 07, 2021, 11:53:00 AM »

I have built several speech amps using the 6N7 as a phase inverter between a 6C5 and push pull 6A3's. It's what I'm currently using in the speech amp of my homebrew rig. This is a very clean sounding hollow state speech amp. My current audio chain is: RE27 mic, Grace design mic preamp, dBx graphic equalizer, 3 CRL audio processing boxes, homebrew speech amp (6SJ7, 6C5, 6N7, PP6A3's), 811A modulators.

I should probably just plug a D104 into the speech amp. Wink

Ron W8ACR
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« Reply #34 on: February 11, 2021, 07:37:17 PM »

how bout this. I doubt the audiophools will be in any hurry.


* wild pig 12x6N7_amp.png (99.65 KB, 2621x895 - viewed 323 times.)
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« Reply #35 on: February 11, 2021, 08:45:29 PM »

Quote
how bout this. I doubt the audiophools will be in any hurry.

A parts list that even I can figure out Tongue Roll Eyes Huh Cool Shocked Grin Cheesy Undecided Wink
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« Reply #36 on: February 12, 2021, 05:10:20 PM »

Up till now, we've been all talking about thermionic emission, vacuum tubes with heaters that either directly or indirectly boil off electrons that are attracted to a positively charged plate. There's another class of tubes, the so-called 'cold cathode' family. 

Cold cathode tubes include some you're familiar with, like a neon lamp, or other discharge lamps, including cold-cathode fluorescent lamps. Neon lamps can light up to tell you the transmitter is turned on, or act as a negative resistance element, typically to stabilize a circuit. Tubes filled with specific mixes of gases are used as voltage regulators; some familiar ones are the 0A3 or 0B2. There's even a few specialized cold cathode devices most of us will never actually see/touch/own:  high speed, high voltage, high current tube switches, which can be used in discharge experiments, pulsed radar systems, and your everyday garden-variety nuclear weapon...

So, for today, we'll keep it simpler, but still unique:  A neon tube, a Nixie or numerical indicator tube, with a twist:

The IN-9/IN-13 family

A linear indicator. A long thin tube; as current through it increases, the lit up area increases in length, so it gives a level like a meter!



Data sheet:
http://www.tube-tester.com/sites/nixie/dat_arch/IN-13.pdf

How it works:
https://www.saltechips.com/lab/theory-of-operation-and-construction-of-the-in-13-nixie-gas-discharge-tube

Some applications/prior art:
https://www.instructables.com/Analog-IN-13-bargraph-Nixie-tube-thermometer/
https://www.die-wuestens.de/rd/IN9-2.pdf
https://www.nixies.us/projects/in-9-vu-meter/
https://www.instructables.com/Nixie-bargraph-clock/

You can find these on eBay, coming from Russia, like many oddball old things like HV capacitors and tubes, for a few bucks and a few weeks for shipping.  They seem kind of cool; I think I may put one in my next transmitter as some kind of level measurement -- modulation, or whatever. Maybe I'll stick it on the front panel of a class E rig, so I can claim it has vacuum tubes!

There you have it -- let's hear your ideas on this unique technology. As always, if you'd like to write up a tube, or suggest a type, please email or message me.

Ed
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« Reply #37 on: February 14, 2021, 08:19:36 PM »

I like those. The VU meters with them have been described on the web. I think the data sheet schematic has certain festures built in, such as not turning on the main cathode intil the starting cathode is consuming an appropriate current.

Speculation on the schematic's working.
 ( http://www.tube-tester.com/sites/nixie/dat_arch/IN-13.pdf )
Taking a stab at this unusual tube:
Please correct me if I have it wrong. It reminds me in part of the current regulator for a 1mW helium neon laser tube used in laserdisc players.

---
Starting cathode operation:
VT1 and VT2 are off.

When the 140V HV is applied from regulated power supply G1, the starting cathode draws current through the starting cathode limited by R1-R2. The starting cathode current is to be limited to 0.11 to 0.15mA. (0.13mA?)

R1 probably will need experimentation depending on VT2 choice. The tube voltage drop from anode to starting cathode is not stated.
Assuming a 0.6V B-E junction drop in VT2, the current through R2 would be about 0.6/30,000 = 0.02mA
Assuming a starting cathode current of 0.13mA, this leaves 0.11mA for the base current of VT2.
VT2 needs beta of >50, so its collector current may be 5.5mA. It's consistent with enough current (0.2 to 4.6mA) to power the tube's main cathode.
R1 is listed as 330K. Starting cathode current of 0.13mA would mean that 42.9V is lost across R1. This would mean that the running voltage drop of the starting cathode-to-anode circuit would be 97.1V.
Once the starting cathode is up to current, the main cathode is started.

Main cathode operation:
The voltage drop across R2 will turn on VT2, completing a path from the emitter of VT1 to GND through R3, R4, and VT2.  
VT1 is biased by R3-R4 to conduct a constant current adjusted by R4, keeping the emitter of VT1 is just ~0.6V below the voltage on the base, that is keeping VT1 ON just enough for Ie=(Vb-0.6)/(R3+R4).

An adjustable base bias voltage for VT1 is provided via R5 from power supply G2.

Power supply G2 need only have a high and low voltage output to GND suitable for biasing VT1 properly so that from ~0 to the maximum length of the tube V is lit as R5 is varied.

If the voltage across VT2 is assumed to be 0.7 and R4 set to 1K Ohm, then the voltage across the 2K Ohm combination of R3+R4 would be 0.4 to 9.2V over the tube's current range as set by R5.

The outputs of power supply G are both positive in polarity with respect to GND. The relative polarity is not shown, but it's likely the less positive output is the top one.

One output is a higher voltage than the other.

This working is about proportional to VT1 regulating the tube current from its min to max ratings, or about 0.2 to 4.6mA to keep within bounds.

C stabilizes the wiper voltage of R5.  

---
The application part would probably be to insert a couple of 1K resistors between R5 wiper and the base of VT1, then couple a modulating voltage there to modulate the current through VT1's collector. The action is to modulate the base voltage, causing the emitter to act as a follower, which will modulate the voltage across the combination of R3-R4-VT2 and thereby modulate the current supplied from the high voltage 140V supply through the main cathode of the indicator tube.


An interesting use for a pair of them might be as a forward/reflected relative power indicator for AM transmitters where the level is always moving. Mounted so the tubes are cathode to cathode behind a panel slot so that FWD power increases the glow to the right and REFL power increases the glow to the left. Appropriate for rack-sized equipment and well lit rooms but only needing 1U.
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« Reply #38 on: February 19, 2021, 08:30:19 PM »

Friday February 19, 2021.  Snowing all over the country this week, leaving time between shoveling out the driveway over and over to look at some nice warm tubes! 

So, while looking for miscellaneous AM stuff on eBay, like modulation transformers, I happened across a military aircraft transmitter mod transformer, although it wasn't the conventional type. It happened, in the pictures, to show the modulator as being a push pull type 829B tube.  Being curious, I looked it up, and there you go, an interesting and semi-available tube. There's a similar tube with the designator 3E29, and there's a Russian version, as well.   

Two beam power tubes in one envelope, with common cathodes, suppressor/beam-forming plates, and screens, and separate plates and grids. Designed for push pull duty, where all that stuff gets tied together anyway, it even has the screen bypass capacitor built-in internally. It can be used for audio as a modulator, running AB1, or an RF amp, plate modulated class C, or other less interesting things like CW or FM.  typical power levels are 44w audio and up to 90w RF per tube (both sections) in a push/pull configuration.

Datasheet:
https://frank.pocnet.net/sheets/049/8/829B.pdf

Some prior art:

Audiophile version: http://www.engineeringradio.us/blog/2019/03/tube-amp/comment-page-1/
AudioFOOL version (note price...):http://www.finaleaudio.com/829b-special
RF, with complete details...https://www.funkamateur.de/tl_files/downloads/hefte/2016/AN%20829B%20DUAL%20BEAM%20POWER%20PENTODE%20HF%20TRANSMITTER.pdf
VHF in the old days:http://n4trb.com/AmateurRadio/GE_HamNews/issues/GE%20Ham%20News%20Vol%2010%20No%206.pdf
FM broadcast-ish: http://www.tubes.rs/pirate-radio-fm-transmitter-rca-829b/
Viking 1 with an 829B (scroll down a bunch):http://amfone.net/AMPX/077.html

So, if this tube sounds interesting, or just looks cool, this should give you some ideas of how you might make it do something as well..

As always, comments welcome. If you have a suggestion or want to describe a tube for a week, please email or PM me.

Ed
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« Reply #39 on: February 27, 2021, 01:53:36 AM »

I'd always thought it would be fun to have one as the modulator and one as the RF amp. The 832 - same, plus as a driver. The high voltage rating and the low screen voltage open many possibilities. I wonder how it would do in the "special class B" setup.
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« Reply #40 on: February 27, 2021, 10:55:45 AM »

Hello again, and here's another type that came up in peripheral conversation this week:

The 6BQ5, or EL84, miniature power pentode.  This 9 pin based tube is good for about 12 watts of audio in P/P mode. It was (and is) used in many lower powered guitar amplifiers, compact stereo/hi-fi amplifiers and so forth. There are many varieties available, from NOS to used to brand new; because it fits a niche in guitar amplification, it is still being sold in music stores.

Wiki article:https://en.wikipedia.org/wiki/EL84

Datasheets:
https://frank.pocnet.net/sheets/049/6/6BQ5.pdf
https://frank.pocnet.net/sheets/129/e/EL84.pdf

Some amplifiers:
https://audioxpress.com/article/a-beginner-6bq5-se-amp
http://diyaudioprojects.com/Schematics/Push-Pull-EL84-6BQ5-6V6-6AQ5-Dynaco-A-410-Tube-Amp-Schematic.htm
http://www.quadesl.com/pdf/sa16.pdf
Eico HF-12:https://www.thetubestore.com/lib/thetubestore/schematics/Eico/Eico-HF-12-Owner-Manual-Schematic.pdf


Some transmitters:
https://nmwilliam.tripod.com/el84.html
oddball FM?AM screen modulated thing: https://www.diyaudio.com/forums/everything-else/221802-tx-fm-6bq5.html
6BQ5's in the modulator:http://www.amwindow.org/tech/htm/eltx.htm

So there you go, another interesting bottle. The 6BQ5 is known for having high gain, making possible cheaper devices by using fewer tubes. Get some and build something!  Be forewarned: as miniature tubes go, this one gets significantly hotter than many -- let it cool off before you pull it out of the socket (yes, this dummy reminded himself of that recently...)

As always, if you have a comment, please comment. If you have an idea for a tube to review, let me know. 

Ed



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« Reply #41 on: March 04, 2021, 09:51:08 PM »

 Along with the 6BQ5 is the 7189. The 7189 can handle higher plate voltage, and replace a 6BQ5. Then combine two 7189's into one Octal envelope with the 6L6GC bulb, and we have the 6DZ7. The 6DZ7 came late to the party, and therefore it was seldom used. It is neat though in that there is 1 cathode pin, and the Screen grids are also tied to a single socket pin.

7189:
http://tdsl.duncanamps.com/show.php?des=7189A

6DZ7:
http://tdsl.duncanamps.com/show.php?des=6DZ7

  I once used a pair of 6DZ7's in a Fischer Tube Amp that had a quad of 7591A's. The 6DZ7's (just 1 per channel) at maximum ratings put out 30w / channel of fantastic audio.

Jim
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« Reply #42 on: March 07, 2021, 07:52:36 AM »

Along with the 6BQ5 is the 7189. The 7189 can handle higher plate voltage, and replace a 6BQ5. Then combine two 7189's into one Octal envelope with the 6L6GC bulb, and we have the 6DZ7. The 6DZ7 came late to the party, and therefore it was seldom used. It is neat though in that there is 1 cathode pin, and the Screen grids are also tied to a single socket pin.

7189:
http://tdsl.duncanamps.com/show.php?des=7189A

6DZ7:
http://tdsl.duncanamps.com/show.php?des=6DZ7

Jim
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I'm going to leave this here as this week's entry.

more data sheets:

https://frank.pocnet.net/sheets/049/7/7189.pdf
https://frank.pocnet.net/sheets/093/6/6DZ7.pdf

There are not as many of these out on eBay, etc, and the 7189 has an audiophile/collector aura, so NOS examples are pricey.  Not every tube can be a bargain!

Here's a lightweight guitar amp: http://img.photobucket.com/albums/v283/jazz347/Tiny_Amp_11.png

From GE, as modulator, page 1:http://www.oestex.com/tubes/Data/ham1.gif
   page 2:http://www.oestex.com/tubes/Data/ham2.gif

and a Heath model featuring the 6DZ7 (direct download pdf link):https://www.vintage-radio.info/download.php?id=597

Thanks to Jim, see you next week!



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« Reply #43 on: March 07, 2021, 07:55:56 AM »

Came across this 832 device, seen below.

on eBay for now, not even very expensive:
https://www.ebay.com/itm/273983168912

Ed


* 832.jpg (159.97 KB, 1200x1200 - viewed 216 times.)
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« Reply #44 on: May 26, 2021, 02:28:34 PM »

I am curious to know what tube will be featured this week.
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« Reply #45 on: May 28, 2021, 12:30:27 AM »

please, give us a tube!
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« Reply #46 on: May 28, 2021, 01:01:00 AM »

I'll jump in.  Big glass tubes are a special fetish with me. Wink

Feast your eyes on the mighty Federal F-128A:

https://frank.pocnet.net/sheets/188/f/F128A.pdf

Move over, 851. Angry

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« Reply #47 on: May 28, 2021, 11:15:12 AM »

Feast your eyes on the mighty Federal F-128A...

Sweet.  A couple of those would keep one warm in the wintertime. (143-watt filaments!  Shocked )
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« Reply #48 on: May 28, 2021, 12:42:03 PM »

Federal F-128A. The poop sheet is dated from 1953 on that tube. I never read anything about it in broadcast transmitters but Federal made their own transmitters and it probably was used in their equipment for overseas transmission of CW & RTTY back in the day? My guess that they were IPA tubes driving the big wet ones!

I see they were in Clifton, NJ. I didn't live far from that city back in 1966. I don't think any major manufacturing was going on in those days. The reason I say this is that I worked most of NE NJ from 1966-1972 as a electronics tech and later as an industrial battery & charger service dude. Yup it was dead in Clifton as industries goes. There was another area called Clifton Park but it was mostly warehousing.

I think Ed was trying to talk about the 832A tube? They seem to popular with the modern head set amplifiers but weren't that popular with hams probably because of the 829B with its higher power capability? After the big war a lot of hams were converting the SCR-522 aircraft VHF transmitters to work on the ham bands but I don't remember what frequencies were in use in them thar days? They used about four of those tubes.  I remember that most hams or at last the more popular ones all had a nick name but that doesn't seem to be the case nowadays. The fact that the 832A is still going strong in audio applications is testimony that the 832A it is a fine US manufactured tube.

  
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« Reply #49 on: May 29, 2021, 11:33:58 AM »

That F-128 is a beautiful tube. Seems very rare. No pictures on the web and none for sale though I didn't dig all the way to the end of the internet.
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AMfone - Dedicated to Amplitude Modulation on the Amateur Radio Bands
 AMfone 2001-2015
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