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THE AM BULLETIN BOARD => QSO => Topic started by: Opcom on January 15, 2021, 08:51:21 PM



Title: Tube of the Week
Post by: Opcom on January 15, 2021, 08:51:21 PM
Tube of the Day, Jan 15, 2021: The 6216

https://frank.pocnet.net/sheets/127/6/6216.pdf
Just happened to find this interesting tube in an old ad.
Military ruggedness,
Designed as an "electronic filter choke" with a 60-65V drop@110mA in Tetrode connection without burning up the screen.
Class A amp @ 3.8W,
Video amp,
Class C oscillator of 8W @ 50MHz.

A 110mA cathode in a 9 pin mintature beam power tube!
1.2A heater @6.3V.

Best of all, it's not expensive. The electronic filter circuit is included in the datasheet.




Is it worthwhile to have a sticky topic "Tube of the Day" ?

Maybe focus on less-known or unusual tubes which are:

* special in some capability/advantage,
* still generally available in experimenter quantities,
* and relatively inexpensive. for example this one cost from $2 to $8 at tube vendors, depending.

what else/


Title: Re: Tube of the Day
Post by: KL7OF on January 16, 2021, 12:03:33 AM
Good topic....I have a few tubes that are interesting ...I'll post them..This is history and actually may be useful in the future...


Title: Re: Tube of the Day
Post by: K8DI on January 16, 2021, 09:36:12 AM
Suggest maybe make a stickied thread with only a daily post, to reduce clutter, and then have members pm the person overseeing it with suggestions or submissions.

That said, an oddball favorite of mine is the 8417...

Ed


Title: Re: Tube of the Day
Post by: Steve - K4HX on January 16, 2021, 05:26:02 PM
Sounds like a great idea. Who wants to be the point man?


Title: Re: Tube of the Day
Post by: W3SLK on January 16, 2021, 08:34:51 PM
Steve said:
Quote
Sounds like a great idea. Who wants to be the point man?
Shouldn't it be 'Pin-man'?  ;)


Title: Re: Tube of the Day
Post by: Steve - K4HX on January 17, 2021, 09:37:15 AM
Opcom has first dibs, but another member has volunteered.

We may want to make this Tube of the Week to allow more time for discussion and reduce the effort in coming up with new/interesting tubes. What say?


Title: Re: Tube of the Day
Post by: Opcom on January 18, 2021, 09:34:48 AM
I agree with a weekly tube for the reasons given. I feel that there need not be much effort searching out tubes unless someone wishes to, and there is certainly a limited number of tubes meeting the criteria of unique, available, and inexpensive.

Though when the 8417 is mentioned, 'inexpensive' is not too applicable as they go for $100 each whereas similar tubes like the 6550 cost much less. To my thinking it's no something I'd experiment with and I've modded audio amps to get away from price extremes.

My aim was for tubes which would be attractive for experimenters because of an unusual characteristic, so in general they should also be available and inexpensive, to encourage uses that are pertinent to the special capability.

If it is to be multiple posts per tube type, then it should be on a weekly basis per type, and posts about a single type of tube should be made only during its actual week or 7 day period, so that once the next tube is posted, the posts for the previous week's tube won't be getting into the current  one. In any case once the new tube is posted, people should refrain from posting on the previous one. That is where a PM to a gatekeeper might be useful.

I'm here sporadically, and though I'm enthusiastic about unusual, useful, and inexpensive tubes, I would be happy to leave gatekeeping to someone who is so interested as to have volunteered for it and is on the board daily or near daily.

That was just my vision as the OP, and I am happy to leave the maintenance, 'rules', and improvements of the topic to the admins and a volunteer.

Thanks,


Title: Re: Tube of the Day
Post by: KA3EKH on January 18, 2021, 11:12:30 AM
If you are going to do “Tube of the Week” my vote for the first week has to be the 807


Title: Re: Tube of the Day
Post by: wb1ead on January 18, 2021, 12:49:22 PM
Hi Patrick & all..gud idea and I do have a couple candidates that I wud like to know more about in the stash..I'm hoping that questions such as where used/intended purpose and such will be part of this section..when I saw the title "Tube of the Day" it brought back in memory of a show I used to watch years ago on ch 4 out of Boston.."Star of the Day"
              I'll be sending in my querys a little later..gud idea Patrick!  73 de DAVE WB1EAD


Title: Re: Tube of the Day
Post by: KD6VXI on January 18, 2021, 01:32:36 PM
8417 is expensive because of Wawassee Electronics.  They used it in amplifiers for RF.  Very non linear amplifiers.

--Shane
KD6VXI


Title: Re: Tube of the Day
Post by: K8DI on January 18, 2021, 03:51:13 PM
8417 is expensive because of Wawassee Electronics.  They used it in amplifiers for RF.  Very non linear amplifiers.

--Shane
KD6VXI

Although I mentioned the 8417, I wasn't suggesting it as an RF tube. It's a beefy pentode designed for ultralinear audio, which it does well, and nobody knows what it is, which is part of its appeal to me. It IS way overpriced in the markets of today. Maybe I should just sell the NOS pairs I have...

Ed



Title: Re: Tube of the Day
Post by: W1RKW on January 18, 2021, 05:11:06 PM
My vote is for tube of the week.


Title: Re: Tube of the Day
Post by: KL7OF on January 18, 2021, 10:41:45 PM
I will drag this one up...we discussed it before...I have 2 FLAME_OTROL tubes sitting on my desk    Steve
http://amfone.net/Amforum/index.php?topic=41867.msg304390#msg304390


Title: Re: Tube of the Day
Post by: Opcom on January 19, 2021, 01:15:11 AM
I like any tube whether it's RF-purposed or not. Takes more than an RF tube to make a radio set.

I find the 8417 interesting personally, Its low grid bias for one thing. just costly but never mind me,

Steve- Announce and let the volunteer loose!!


Title: Re: Tube of the Day
Post by: Chuck...K1KW on January 19, 2021, 04:18:06 PM
The 8417 is an excellent audio tube and perfect for modulator use.  My Johnson Rangers have been converted to them using a phase inverter instead of that lousy driver transformer.


Title: Re: Tube of the Day
Post by: W7TFO on January 19, 2021, 09:15:41 PM
I nominate the 7355.

A gutsy pentode with low distortion/high output audio power. 8)

73DG


Title: Re: Tube of the Day
Post by: W3SLK on January 24, 2021, 08:42:41 AM
Well, lets get this party started! I figured the best place was the one of the most common and venerable tubes. Forgive me for using information from Wikipedia, but it gave a nice short and concise description of it. I think if others have more to add they should do it. Enough bloviating so I present to you the ever so proud 807:

Audio uses

807s were used in audio power amplifiers, both for public address and Hi-Fi application, usually being run in push-pull pairs in class AB1 or AB2 giving up to 120 watts of usable power. The plate voltage limit is 750 volts and the screen grid limited to 300 volts. Because of the 300 volt screen grid voltage limit, the 807 cannot be triode connected for high power applications. Failure to observe this precaution will cause screen grid failure. Less commonly a single 807 was used in a pure class-A, single-ended audio output stage delivering about 10 watts.
RF uses

The 807 is fully rated to 60 MHz, derated to 55% at 125 MHz in Class C, Plate-modulated operation, thus they were popular with amateur radio operators (radio hams). In this application a single 807 could be run in class-C as an oscillator or amplifier which could be keyed on and off to transmit Morse Code in CW mode. For voice transmission on AM a final amplifier with one or more 807s, up to about four, could be connected in parallel running class-C. Connecting multiple 807s in parallel produced more power to feed to the antenna. Often the modulator stage (simply a transformer-coupled audio amplifier for A.M., with the secondary of its output transformer in series with the anode supply of the final amplifier), was also constructed using 807s. Many hams found multiple paralleled 807s a cheaper alternative to a single larger valve, such as a single 813, as many military surplus 807s became available cheaply after World War II. In Australia 807s are affectionately referred to as "stubbies" because they are almost as ubiquitous as that common Australian beer container.
The class C operational values in the info box at the right are for anode modulated A.M. operation; for CW operation a maximum anode voltage of 600 is permissible, whereby the anode current increases to 100 mA and the anode/plate dissipation rises to 25 watts. The screen voltage is the same, at 300, but its dissipation rises to 3.5 watts. 37 watts of R.F. power is produced from 220 mW of drive but only a 50% duty cycle is allowed. The maximum allowable negative control grid, g1 excursion allowable is -200 volts and average control grid current is 5mA in both A.M. and CW modes.[1] Later versions could be used on CW with a supply voltage up to 750 V and a current of 100 mA to produce 50-55 watts of output power.
Differences from 6L6

The electrically similar 6L6 was not favored by hams because high transient voltages on the anode when operating in class C could cause a flashover between pins 2 and 3 on the octal base, whereas the 807 had the anode connected to a top cap, physically distant from all the base pins.
Derivatives

The 1624 (VT-165) is an 807 variant with a directly heated filamentary cathode operating at 2.5 V, 2 A.

The 1625 (VT-136) is an 807 variant with a 12.6 V heater and a 7-pin base. These tubes were used as RF power amplifiers in some of the SCR-274 and AN/ARC-5 "command set" transmitters of WW2. Postwar, 1625 tubes flooded the surplus market, and were available for pennies apiece. Surplus 1625s found some commercial use, notably the use of a pair as modulator tubes in the Heathkit DX-100 amateur transmitter.

The HY-69 is an 807 variant with a 5-pin base and a directly heated filamentary cathode operating at 6.3 V, 1.6 A.

The 5933/807W is a ruggedized military version of the 807. It uses a shorter, straight-sided T12 bulb, which provides better element support for improved microphonics and shock/vibration resistance.

The ATS-25 is a military version with ceramic base.

The Г-807 (G-807) is a Soviet/Russian version. The 6П7С (6P7S) is similar to Г-807, but with an 8-pin octal base.

The 807 also found some use as a horizontal output tube in early TV receivers, particularly those manufactured by DuMont. The 807 design (with some "value engineering" to reduce production cost) was the basis for the first application-specific horizontal sweep tubes such as the 6BG6G and 6CD6G. The redesign mainly involved the omission of some of the internal RF shielding, and the substitution of a bakelite Octal base for the micanol or ceramic 5-pin.

In turn, these low cost sweep tube derivatives found some use as RF power amplifiers in homebrew amateur radio transmitters in the 1950s.
Slang

Ham operators in the US sometimes use the term "807" to refer to bottles of beer due to the shape of the tube.[2][3]


Title: Re: Tube of the Day
Post by: WA2SQQ on January 24, 2021, 05:17:49 PM
In preparation for this discussion I just put 6 PCs in the fridge. Their current condition is cold and wet, perhaps a bit gassy!


Title: Re: Tube of the Day
Post by: Steve - K4HX on January 24, 2021, 10:09:45 PM
K8DI has graciously volunteered to moderate the Tube of the Week thread.


Title: Re: Tube of the Day
Post by: Opcom on January 24, 2021, 10:24:06 PM
An old radio operator who was a policeman+radio op during WWII told me that one reason for the 1625's different basing and socket was partly an attempt to prevent an 807 black market.

The other reasons being the 1625's 12.6V heater and giving access to its beam forming plates.

He was very serious about the pilfering/black market thing though. Anyone shed light on that?



Also, Thank you K8DI for volunteering!


Title: Re: Tube of the Week
Post by: W7TFO on January 25, 2021, 10:47:45 AM
I remember an old tube manual stating the 7-pin base on the 1625 was used as it was retained by the socket better for aircraft equipment.

73DG


Title: Re: Tube of the Week
Post by: W2PFY on January 25, 2021, 12:40:57 PM
I think I remember something about the 1625 where a hole was put in the side of the base to unhook some wire so it could be used in a amplifier for SSB back in the day? Was it the 1625 or the other great tube known as a 837? It may have been to disconnect the beam forming plates?  Or maybe to make it a tetrode from a pentode? I give up, does anyone know?   :o :o



Title: Re: Tube of the Week
Post by: KY4SP on January 25, 2021, 03:07:05 PM
I think I remember something about the 1625 where a hole was put in the side of the base to unhook some wire so it could be used in a amplifier for SSB back in the day? ...

here- https://www.robkalmeijer.nl/techniek/electronica/radiotechniek/hambladen/qst/1955/06/page21/index.html


Title: Re: Tube of the Week
Post by: K8DI on January 26, 2021, 09:03:13 AM
Hello to all who are following this topic, a grand idea from Opcom.  In the meantime, I volunteered to take point on it, and W3SLK put forth a wonderful first entry.

Here's what I propose I'll be doing:

One a week, followed by some comments.

For the most part, available, appropriately priced tubes, both popular and lesser known.  Once in a while, something historical that may not be as available and thus more expensive, and once in a while something bigger, which is not inexpensive. Example of the most part: 807, 6AG7, EL34. Historical: 803, 46. Bigger: 813, 3-500Z, 4-1000A.

If you have a suggestion, or want to write up a tube like W3SLK did, please PM me, or email me at the address listed here and on QRZ. My plan is to post a new one every Friday.

Ed



Title: Re: Tube of the Week
Post by: Opcom on January 26, 2021, 01:22:42 PM
I suggest a 'read before posting' post at the top, or something like that, which includes the proposed or accepted guidelines or rules for this topic.


Title: Re: Tube of the Week
Post by: W3SLK 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.


Title: Re: Tube of the Week
Post by: K8DI 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


Title: Re: Tube of the Week
Post by: W2PFY on January 28, 2021, 11:19:48 AM
Quote
here- https://www.robkalmeijer.nl/techniek/electronica/radiotechniek/hambladen/qst/1955/06/page21/index.html

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

Terry
W2PFY



Title: Re: Tube of the Week
Post by: K8DI 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 (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 (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 (https://www.frostburg.edu/personal/latta/ee/6cl6xmtr/6cl6xmtr.html)
WA5BDU:  http://pages.suddenlink.net/wa5bdu/2_tube.htm (http://pages.suddenlink.net/wa5bdu/2_tube.htm)
AF4K (Incomplete/old page, unfortunately the owner is SK):  http://s88932719.onlinehome.us/2e26.htm (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/ (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


Title: Re: Tube of the Week
Post by: w4bfs 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


Title: Re: Tube of the Week
Post by: w8khk 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?


Title: Friday February 5, 2021 Tube of the Week -- the 6N7
Post by: K8DI 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 (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 (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 (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 (https://bama.edebris.com/download/lettine/240/240.pdf)
One tube, push pull: https://www.kb6nu.com/a-one-tube-push-pull-transmitter/ (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 (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 (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 (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











Title: Re: Tube of the Week
Post by: W7TFO on February 06, 2021, 01:54:20 PM
Yep, it's predecessor is the 53. 

Can make 10 honest watts in PP cl "B".  :D

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

73DG


Title: Re: Tube of the Week
Post by: W8ACR 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. ;)

Ron W8ACR


Title: Re: Tube of the Week
Post by: Opcom on February 11, 2021, 07:37:17 PM
how bout this. I doubt the audiophools will be in any hurry.


Title: Re: Tube of the Week
Post by: W2PFY 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 :P ::) ??? 8) :o ;D :D :-\ ;)


Title: February 12, 2021: "And now, for something completely different"...
Post by: K8DI 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!

(https://www.elektormagazine.com/assets/upload/images/14/20180605094307_160705-51A.jpg)

Data sheet:
http://www.tube-tester.com/sites/nixie/dat_arch/IN-13.pdf (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 (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.instructables.com/Analog-IN-13-bargraph-Nixie-tube-thermometer/)
https://www.die-wuestens.de/rd/IN9-2.pdf (https://www.die-wuestens.de/rd/IN9-2.pdf)
https://www.nixies.us/projects/in-9-vu-meter/ (https://www.nixies.us/projects/in-9-vu-meter/)
https://www.instructables.com/Nixie-bargraph-clock/ (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


Title: Re: Tube of the Week
Post by: Opcom 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.


Title: Another Friday, another tube....accidental eBay find, the 829B
Post by: K8DI 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 (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/ (http://www.engineeringradio.us/blog/2019/03/tube-amp/comment-page-1/)
AudioFOOL version (note price...):http://www.finaleaudio.com/829b-special (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 (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 (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/ (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 (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


Title: Re: Tube of the Week
Post by: Opcom 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.


Title: February 26, 2021 -- another tube for your consideration
Post by: K8DI 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 (https://en.wikipedia.org/wiki/EL84)

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

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


Some transmitters:
https://nmwilliam.tripod.com/el84.html (https://nmwilliam.tripod.com/el84.html)
oddball FM?AM screen modulated thing: https://www.diyaudio.com/forums/everything-else/221802-tx-fm-6bq5.html (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 (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





Title: Re: Tube of the Week
Post by: WD5JKO 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
Wd5JKO


Title: March 5, 2021 Tube of the Week, via WD5JKO
Post by: K8DI 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
Wd5JKO

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/049/7/7189.pdf)
https://frank.pocnet.net/sheets/093/6/6DZ7.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 (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 (http://www.oestex.com/tubes/Data/ham1.gif)
   page 2:http://www.oestex.com/tubes/Data/ham2.gif (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 (https://www.vintage-radio.info/download.php?id=597)

Thanks to Jim, see you next week!





Title: Re: TOTW, 829B variation, the 832:
Post by: K8DI 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 (https://www.ebay.com/itm/273983168912)

Ed


Title: Re: Tube of the Week
Post by: w8khk on May 26, 2021, 02:28:34 PM
I am curious to know what tube will be featured this week.


Title: Re: Tube of the Week
Post by: Opcom on May 28, 2021, 12:30:27 AM
please, give us a tube!


Title: Re: Tube of the Week
Post by: W7TFO on May 28, 2021, 01:01:00 AM
I'll jump in.  Big glass tubes are a special fetish with me. ;)

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

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

Move over, 851. >:(

73DG


Title: Re: Tube of the Week
Post by: N5RLR 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!  :o )


Title: Re: Tube of the Week
Post by: W2PFY 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.

  


Title: Re: Tube of the Week
Post by: Opcom 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.


Title: Re: Tube of the Week
Post by: KL7OF on May 29, 2021, 08:21:25 PM
Nice Dennis...do you have one in your collection?   I like the big spade connections on the base..


Title: Re: Tube of the Week
Post by: W7TFO on May 29, 2021, 09:30:04 PM
I count 4 here.  Indeed, unicorns. ;)

Need to get pix.

73DG


Title: Re: Tube of the Week
Post by: N5RLR on May 30, 2021, 11:45:44 PM
New week, new tube. Let's go the other direction.  Let's go down in size. ;)
 
The Nuvistor.
 
The Nuvistor was a type of vacuum tube announced by RCA in 1959. Most of them were basically thimble-shaped, but somewhat smaller than a thimble, and much smaller than conventional tubes of the day. Their size almost approached the compactness of early discrete transistors. Triodes and a few tetrodes were made. The tube was made entirely of metal with a ceramic base.
 
Nuvistor tetrodes were taller than their triode counterparts. Manufacturing them required special equipment, since there was no intubation to pump gases out of the envelope. Instead, the entire structure was assembled, inserted into its metal envelope, sealed and processed in a large vacuum chamber with simple robotic devices. It has been said that this process made them more expensive than competing glass tubes.
 
Some Nuvistors were designed to be used in military equipment (some say that this was their intended application, with consumer- and experimenter use being a nice bonus -- and cover story). They were used in the Ranger spacecraft of 1961-65, and interestingly by the USSR in their MiG-25 fighter jet, presumably to harden the fighter's avionics against radiation.
 
Nuvistors were among the highest performing small signal-receiving tubes. They featured excellent VHF and UHF performance plus low noise figures, and were widely used throughout the 1960s in television sets, radio- and high-fidelity equipment primarily in RF sections, and oscilloscopes. They competed with the solid state revolution, and along with GE's Compactron, probably held it at bay for a few years. RCA discontinued their use in television tuners for its product line in late 1971. As of this writing I've not found exactly when their production ceased.
 
Radio amateurs also found use for Nuvistors, mainly in VHF/UHF converters. QST published a flurry of articles using them in the early 1960s. RCA Ham Tips, of course, published several Nuvistor projects, such as a 2-Meter transceiver in its Spring 1965 issue.
 
I first learned of them in the late 1970s, when I found a copy of the 1966 ARRL Handbook in my high-school library.  Therein was a construction project for a portable 420-Mc. transceiver using a Nuvistor as superregenerative detector and modulated oscillator. 250 mW plate input at 45 VDC!  :D
 
Types:
 
* 7586 - First one released, medium-mu triode
* 7587 - Sharp-cutoff tetrode
* 8056 - Triode for low plate voltages
* 8058 - Triode, with plate cap & grid on shell, for UHF performance
* 7895 - 7586 with higher mu
* 2CW4 - Same as type 6CW4, but with a 2.1 V / 450 mA heater.
* 6CW4 - High-mu triode, most common one in consumer electronics
* 6DS4 - Remote-cutoff 6CW4
* 6DV4 - Medium-mu, intended as UHF oscillator, shell sometimes gold plated
* 8393 - Medium-mu, 12.6 V filament
* 13CW4 - Same as 6CW4, but with 12.6 V / 230 mA heater


Title: Re: Tube of the Week
Post by: Opcom on June 26, 2021, 11:22:56 AM
We used to snag the nuvistors out of old color TV sets when they were scrapped. Quite a few older equipments still use them like CEI panoramic receivers and oscilloscopes.


Title: Re: Tube of the Week
Post by: K9PNP on June 30, 2021, 05:38:09 PM
Have a couple left in stock, I think.  Common in the 6M AM equipment like the Lafayette  HA-460 of the late 60's.  Still available from some of the tube dealers.  IIRC, replaced the 6AK5 and others as receiver RF amplifier.  Low noise, reasonable gain.  Of course, the noise floor was considerably lower then, so equipment noise did make a difference.


Title: Re: Tube of the Week
Post by: Opcom on July 18, 2021, 12:37:52 AM
How about something that is 77 years old, yet advanced at its time and still powerful for its size?

The week's about up.. but I'd like to highlight the 8025 (8025A, and the 8012 /A having identical curves and ratings)

The 8025 is not common in ham homes, but 'large quantities' are available NOS online for $35 from a large surplus sales vendor so it's overlooked. I bought a box of NOS specimens at an antique radio auction for a song and people don't seem to have any idea what to do with them. It's a nice looking tube!

The 8025 was made by RCA and GE.

It was first used in WWII.
http://www.qrp.gr/technology/linearuhf/High_f.pdf
That might explain the original RCA data having a copyright of 1943, but the datasheet having its release date in 1945.

Plenty of pictures available:
https://www.google.com/search?q="8025"+vacuum+tube&source=lnms&tbm=isch&sa=X
Nice looking, eh?

The 8025A is a small, glass, directly heated 1000V triode with 40 Watt plate, a 6.3V, 1.92A filament, requires bias, and is good for up to 500MHz at full input and reduced input to 600Mhz. The filament center tap is not for connection to ground or to a filament transformer CT, but for an RF bypass scheme to minimize lead inductance.

Its advantages for UHF work are very short and direct grid and plate leads which come out both sides of the envelope.

The 8025/A has 1/4" plate and grid caps and a 'small 4 pin' base, and the 8012/A has grid and plate pins instead of caps, and flying leads for the filament.

It requires forced air cooling for CCS ratings, and is rated for 30W ICAS on the plate with convection cooling. Maximum plate current rating is 80mA according to GE.

Typical AM operation as a class C amp show 22W output at Carrier level.

Data sheets:
1943: https://frank.pocnet.net/sheets/201/8/8025A.pdf  - best info about care and feeding of the tube.
1945: https://frank.pocnet.net/sheets/049/8/8025A.pdf
1945: https://frank.pocnet.net/sheets/049/8/8012A.pdf

It's intended for class C operation and no modulator or linear amp ratings are given.

For those QRP interests and others wanting to play with it at zero bias, the curves show that 400V on the plate results in 22 Watts dissipation. 300V gives 10.5W dissipation.
It could be a good experiment to try as a class AB2 or B amplifier. For its size it seems like an electrically rugged tube.

The thoriated tungsten filament is a plus for that bright glow. I think the plate is tantalum. For forced air cooling, the data sheet only says that air should be directed at the bulb. These are not intended to be supported or stressed by inflexible connectors attached to their plate and grid connections.


Title: The 4-400A, a big glowing tube!
Post by: K8DI on July 22, 2021, 02:59:28 PM
Hello folks!

How about this one:  the 4-400A. A tetrode, 400w plate dissipation, high gain, low drive.

(https://i.pinimg.com/originals/7f/9a/9e/7f9a9e6f56c908d8064d1239a8a98360.jpg)

Data sheet:
https://frank.pocnet.net/sheets/088/4/4-400A.pdf (https://frank.pocnet.net/sheets/088/4/4-400A.pdf)

A place it was used:
The RCA BTA-1R1 broadcast transmitter
(https://www.engineeringradio.us/blog/wp-content/uploads/2012/04/RCA-BTA1AR.jpg)
manual:  https://bama.edebris.com/manuals/rca/bta1r1/ (https://bama.edebris.com/manuals/rca/bta1r1/)
Found in a fun catalog:  https://worldradiohistory.com/Archive-Catalogs/RCA/RCA-Transmitting-1962.pdf (https://worldradiohistory.com/Archive-Catalogs/RCA/RCA-Transmitting-1962.pdf)

Some other applications:
600m linear: http://w5jgv.com/4-400A_600M_amplifier/ (http://w5jgv.com/4-400A_600M_amplifier/)
Old magazine article for an amp: https://www.robkalmeijer.nl/techniek/electronica/radiotechniek/hambladen/qst/1961/01/page33/index.html (https://www.robkalmeijer.nl/techniek/electronica/radiotechniek/hambladen/qst/1961/01/page33/index.html)

There are hundreds of posts on here that mention the 4-400a, and I am certain there are more than a few AM'ers talking on the air on them even now.  New tubes are available, but expensive. Used are in the usual places. I just made arrangements to buy several, with the rest of the transmitter included.....more on that elsewhere.

I'd like to hear from some of the big guns here about their favorite large tube.. Anyone?  Bueller?

Ed K8DI




Title: Re: The 4-400A, a big glowing tube!
Post by: N5RLR on July 22, 2021, 09:16:15 PM
Found in a fun catalog:  https://worldradiohistory.com/Archive-Catalogs/RCA/RCA-Transmitting-1962.pdf (https://worldradiohistory.com/Archive-Catalogs/RCA/RCA-Transmitting-1962.pdf)

Now there's a Wish Book!  ;D


Title: Re: Tube of the Week
Post by: Detroit47 on July 27, 2021, 12:10:15 PM
i'm surprised no one had anything to say about the 4-400. Or it's predecessor the 4-250 which makes appearances in the famous KW-1. Not to forget the 4-125 in the 30K-1. The Johnson product line makes full use of 4-250 in the Thunderbolt, 500 and, Desk KW. I believe that most of these rigs went to the 4-400 in later production. There is another giant in the glass family of Tetrode's the 4-1000.  The 4-1000 is truly in a class by itself. The tube just loves Hi voltage 6000 make them smile. It's to bad they are getting expensive 100 bucks used to get you a good tube those days are all gone. I know there is a lot of fellows  on this board that have built plate modulated rigs with these. Not to mention there uses as a linear amplifier tube. Show us some pictures of your 4x1 rigs don't hide those big legged girls.

Johnathan N8QPC


Title: Re: Tube of the Week
Post by: K1JJ on July 28, 2021, 12:19:27 PM
There is another giant in the glass family of Tetrode's the 4-1000.  The 4-1000 is truly in a class by itself. The tube just loves Hi voltage 6000 make them smile. It's to bad they are getting expensive 100 bucks used to get you a good tube those days are all gone. I know there is a lot of fellows  on this board that have built plate modulated rigs with these. Not to mention there uses as a linear amplifier tube. Show us some pictures of your 4x1 rigs don't hide those big legged girls.

Johnathan N8QPC


ahhhh..... 4-1000As.  That's my choice for  "Tube of the Week."

Here's Fabio II  -  a working 4-1000A plate modulated construction project.  (125K hits on this BB)     A class C pair plate modulated by a pair.     I also run a pair in grid driven linear. (Rico Suave II)     4X1s get my vote as the coolest and most strapping glass tube for ham radio use.   (Followed by the 813)

http://amfone.net/Amforum/index.php?topic=33816.0


And then came "Quadzilla" .... quad 4X1s in linear service:
http://amfone.net/Amforum/index.php?topic=18616.0

4-1000A data sheet:
http://www.tubecollectors.org/eimac/archives/41000a(52).pdf


The beginning of Fabio II -   and Quadzilla linear running... #3 tube was soft when this picture was taken:


Title: Re: Tube of the Week
Post by: K1JJ on July 28, 2021, 12:46:19 PM
Here's some info on operating 4X1s in linear service, GG included:

http://amfone.net/Amforum/index.php?topic=32823.0



This is a rare notice from Eimac concerning GG 4-1000A linear service:

http://amfone.net/Amforum/index.php?topic=18634.0



There is more 4X1 construction info on this BB by doing a 4-1000A search.


Testimonial: In 50 years time, I've bought both new and used 4-1000As;  always ran air chimneys and was never really careful with parameters. I did my share of piss-beating them at times.  Except for one soft tube that I bought that way, I have never had a bad 4X1 tube in all that time.  (same goes for 813s)  


T


Title: Re: Tube of the Week
Post by: K1JJ on July 28, 2021, 02:18:56 PM
And, Rico Suave II, the GG pair of 4X1s using regulated screen and grid supplies.   I found that running regulated screen  voltage in GG improved IMD.  The grid did not need to draw much current, which is always an improvement.


http://amfone.net/Amforum/index.php?topic=34543.0


Title: Re: Tube of the Week
Post by: Opcom on October 07, 2021, 01:17:00 AM
The 5787WA gas regulator. 18 of them came to me in a box of random NOS tubes.

A subminiature gas regulator in a T3 (3/8" dia) envelope about 2" long. It's a ruggedized type rated 98V @ 5-25MA.

These can be had for about $5, and $3 in quantity of >100. 

This little known tube is great for tight spaces and firing is supposedly not affected by incident light.

A possible use in addition to typical shunt regulation duties could be in place of a customary neon lamp for DC coupled vacuum tube circuits and voltage limitation at the front ends of receivers where its higher current ratings could give much increased life. YMMV.
AMfone - Dedicated to Amplitude Modulation on the Amateur Radio Bands