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Author Topic: Tales about the Mighty 6L6  (Read 3790 times)
AK0B
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Posts: 267




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« on: October 23, 2017, 09:15:59 AM »

The Mighty 6L6

Back in the 50’s when I first got my  novice license,  WN9IFZ, a lot of the guys used a homebrew 6L6 transmitter.  It was common to draw the circuit on the back of a QSL card.  That’s how I got the schematic.

I ran it with 525 vdc on the plate and drew 100 ma, man did it get warm. In the winter it heated up my operating table which was in an old shed.  My mom was certain lightening would destroy it and she didn’t want the antenna running into the house.  The main component was a single 6L6 and a 200 ohm 25 watt resistor.  Everyone seem to have an old 6L6 or two from an old broken radio in the trash.  The local junk yard back then took everything.  It was a business left over from WWII.  They sold a box of tubes anywhere from twenty five cents a box to a nickel a piece.  I trade some pop (soda) bottles in at the grocery store for two cents an piece and had enough money to but two of them.  My antenna was made from the copper wire from an old car coil. It had couple hundred feet of #22 wire or there about.

Recently, I discovered those 6L6 transmitters were not a Novice invention seems back in 1939 the QST tech editor, W8QBW wrote an article about a Runt sixty or QSL sixty in Sept issue.  He powered his with a 600 vdc supply at 200 ma.  WOW, I expect he could heat up a room. He worked Mexico and Canada from Michigan with 589.  Said his cost $3.86 plus the cost of a crystal and a 6L6.
 
Stan AK0B   
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N8AUC
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Posts: 313




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« Reply #1 on: October 23, 2017, 03:32:31 PM »

Funny, but my first transmitter used a 6L6 for a final amp.
It ran about 30 watts input if I remember. 450 volts on the plate at about 75 MA.
Used a 5763 as a crystal oscillator.
I found the plans in an old book at the public library.

That radio worked pretty well. Good times as a novice 40 years ago.

73 de N8AUC
Eric
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KM1H
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Posts: 2479




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« Reply #2 on: October 23, 2017, 05:51:40 PM »

Mine was a 6AG7 6L6 right out of a 51-53 ARRL HB from a used book store, this was in 55 and I dont remember the exact year.

The 6L6 came out in 3/24/36 in the first release of the new metal octal tubes. The 6L6G was released on 6/8/36 and both were instant hits with the hams.

Carl
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G3RZP
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Posts: 8123




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« Reply #3 on: October 24, 2017, 02:13:46 AM »

With a top cap plate connection, the 6L6G became an 807. I ran one of those on 40m: 1750 on the plate 750 on the screen and about -200 of fixed bias. Drove it with a 6L6G: about 225 watts input and around 170 out with a nice red glow if you held the key down for too long.....

I read somewhere that the 1625 had the 7 pin base so that they couldn't get muddled with 807s - which seems unlikely, but you never know.
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N2DTS
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« Reply #4 on: October 24, 2017, 05:17:16 AM »

My first rig was a single tube 6146 out of the 1969 handbook.
Cant remember where I got the 6146?
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KM1H
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Posts: 2479




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« Reply #5 on: October 24, 2017, 08:15:19 AM »

Quote
I read somewhere that the 1625 had the 7 pin base so that they couldn't get muddled with 807s - which seems unlikely, but you never know.

The extra pins were used to hold the tubes in the sockets during battle conditions......seriously
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K8AXW
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« Reply #6 on: October 24, 2017, 10:04:38 AM »

Back in the day, I heard some used the 6L6s upside down in a bucket of water to cool them!   Roll Eyes
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K1ZJH
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Posts: 3303




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« Reply #7 on: October 24, 2017, 07:52:16 PM »

Mine was a 6AG7 6L6 right out of a 51-53 ARRL HB from a used book store, this was in 55 and I dont remember the exact year.

The 6L6 came out in 3/24/36 in the first release of the new metal octal tubes. The 6L6G was released on 6/8/36 and both were instant hits with the hams.

Carl

My Micamold XTR-1 uses the same tube lineup.

Pete
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G3RZP
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Posts: 8123




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« Reply #8 on: October 25, 2017, 03:32:13 PM »

I suspect that the most produced power tubes ever were the 6L6/807/1625s, although a lot of TV sweep tubes were based on the design, and could be considered as close relatives. It seems practically every country with a tube manufacturer copied the 807!
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VK2TIL
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Posts: 535




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« Reply #9 on: October 25, 2017, 07:00:22 PM »

The 6L6GC was capable of dissipating 25% more power than the 'GB; this was due to the five-layer metal composite used in the 'GC plate.

It's of interest that this five-layer composite material was made by the then-novel process of explosive forming.

http://n4trb.com/AmateurRadio/GE_HamNews/issues/GE%20Ham%20News%20Vol%2015%20No%201.pdf

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GW3OQK
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Posts: 386




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« Reply #10 on: October 26, 2017, 05:21:57 AM »

My 1945 ARRL Handbook has a chapter on the War Emergency Radio Service. Amateurs built and used transmitters and receivers for 112 to 116 Mc in Civil Defense. The 6L6 features as a modulator. Class B was recommended but the modulation transformer was "practically unobtainable" so Class A 10H choke modulation was an alternative. The pictures show black metal tubed 6L6s. A transmitter-receiver built into a car glove compartment used 6V6 as RF oscillator modulated by the receive side 6V6. I wonder if any WERS home brew gear has survived.
73
Andrew
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AC7CW
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Posts: 967




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« Reply #11 on: October 26, 2017, 01:13:59 PM »

I remember when it seemed like every other magazine I got had a 6L6 diy article... I could get an ARC5 for less than I could buy the parts and have a random wire tuner to boot, never build any 6L6 projects...
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Novice 1958, 20WPM Extra now... (and get off my lawn)
AA4PB
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« Reply #12 on: October 26, 2017, 01:39:05 PM »

The 6M AM transmitter that I built in 1960 used a pair of 6L6GTs push-pull in the modulator.
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Bob  AA4PB
Garrisonville, VA
G3RZP
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Posts: 8123




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« Reply #13 on: October 27, 2017, 09:46:43 AM »

Pre WW2, my father bought a pair of Raytheon 6L6Gs in a shop in Birmingham - they were quite cheap because in those days there were a lot more dollars to the pound than now. They still work with practically full emission. I also have a pair of unused metal 6L6's still in the cardboard tube cartons with a 1944 date code and US Navy contract number.....
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KM1H
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Posts: 2479




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« Reply #14 on: October 28, 2017, 07:43:31 AM »

My next and last 6L6 project was also in 56 as modulators for a 829B on 6M. Lots of other gear Ive had/have here came with 6L6's including HP.

I never built anything with an 807 altho the TBS-50D, Viking I, II CDC, and 32V2 here use them as modulators. A Viking Adventurer and a Globe 90 use them for RF.
I did build a 5 tube GG amp with modified 1625's, one driving 4 and a CE 10B transmitter. Another amp used 4 837's in GG at 800V, those are a close relation and are true pentodes as is the 42 and 6F6 which also are good at RF.

I went to the 2E26/6146 for homebrew rather than fight with 807 instability which I knew little about in the dark ages but read/heard many horror stories.
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