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Tube of the Week




 
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Opcom
Patrick J. / KD5OEI
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« 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/
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Radio Candelstein - Flagship Station of the NRK Radio Network.
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« Reply #1 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...
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K8DI
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« Reply #2 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
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Steve - K4HX
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« Reply #3 on: January 16, 2021, 05:26:02 PM »

Sounds like a great idea. Who wants to be the point man?
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W3SLK
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« Reply #4 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'?  Wink
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Mike(y)/W3SLK
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« Reply #5 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?
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Opcom
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« Reply #6 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,
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Radio Candelstein - Flagship Station of the NRK Radio Network.
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« Reply #7 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
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wb1ead
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« Reply #8 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
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« Reply #9 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
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K8DI
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« Reply #10 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

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« Reply #11 on: January 18, 2021, 05:11:06 PM »

My vote is for tube of the week.
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Bob
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« Reply #12 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
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Opcom
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« Reply #13 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!!
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« Reply #14 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.
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« Reply #15 on: January 19, 2021, 09:15:41 PM »

I nominate the 7355.

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

73DG
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« Reply #16 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]
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Mike(y)/W3SLK
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« Reply #17 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!
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« Reply #18 on: January 24, 2021, 10:09:45 PM »

K8DI has graciously volunteered to moderate the Tube of the Week thread.
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Opcom
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« Reply #19 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!


* 807-1624-1625.png (21.65 KB, 700x276 - viewed 188 times.)
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Radio Candelstein - Flagship Station of the NRK Radio Network.
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« Reply #20 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
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« Reply #21 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?   Shocked Shocked

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« Reply #22 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
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K8DI
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« Reply #23 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

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Opcom
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« Reply #24 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.
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