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 Post subject: octal equivelent to a 12AT7 tube?
PostPosted: Jun Fri 21, 2019 8:03 pm 
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Joined: Jan Fri 04, 2019 11:32 pm
Posts: 34
Location: Sheridan, Wyoming
I need a high mu octal, single triode to go along with my 12j5gt triode, to replace the 12AT7, 9-pin tube. I am going to use 2 single triodes rather than a duo triode. I think the 12sf5gt would be ok, but I really hate to change the filiment wiring for the 12sf5gt{pins 7 and 8}from my present{pins 2 and 7} I plan to use the single triode as a grounded grid rf amplifier tube.I will use a 12j5gt,which I already have on hand, as a detector tube. Any help appreciated!...... William


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 Post subject: Re: octal equivelent to a 12AT7 tube?
PostPosted: Jun Sat 22, 2019 1:55 am 
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Joined: Jan Thu 01, 1970 1:00 am
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The 12F5 is same tube as 12SF5 but has a top cap.

12SL7GT is a duo triode, has heater on 7 & 8.

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 Post subject: Re: octal equivelent to a 12AT7 tube?
PostPosted: Jun Sat 22, 2019 2:15 am 
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Location: Tucson, Arizona U.S.A.
You might have trouble depending on the frequency you are interested in. The 12AT7 is intended for VHF use while most octal tubes are for much lower frequencies. There are a few VHF octal tubes like the HY615 but I don't know without looking it up how close that is to a 12AT7.

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 Post subject: Re: octal equivelent to a 12AT7 tube?
PostPosted: Jun Sat 22, 2019 3:33 pm 
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Joined: Jan Tue 16, 2007 7:02 am
Posts: 3458
Location: Lexington, KY USA
Might you use a Loktal tube? There were several VHF Loktals.

Ted


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 Post subject: Re: octal equivelent to a 12AT7 tube?
PostPosted: Jun Sat 22, 2019 6:28 pm 
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Location: Dayton Ohio
I know it doesn't help being that it is not a triode, but the WE-717A which was used mostly in WWII, but was also used in the consumer market such as the FM converter sold by E. H. Scott.
It is a 6AK5 VHF amplifier pentode in Octal form.

It may have been a Western Electric design, but most were manufactured by Raytheon or Tung-Sol.
It is not a tube prized by the Western Electric crazies. :lol:

-Steve

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 Post subject: Re: octal equivelent to a 12AT7 tube?
PostPosted: Jun Sat 22, 2019 9:56 pm 
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Joined: Sep Tue 15, 2015 1:16 am
Posts: 883
Location: 18424 PA
High mu would be 12sc7, or lower 12sl7.


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 Post subject: Re: octal equivelent to a 12AT7 tube?
PostPosted: Jun Sun 23, 2019 3:38 am 
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Location: Perrysburg, OH, 43551 U.S.A.
No one has asked what frequencies you want to receive. Granted, a grounded grid amplifier implies higher frequencies, but is this true? The expected frequency range you plan to amplify will help determine the tube that can be successfully substituted.
John

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 Post subject: Re: octal equivelent to a 12AT7 tube?
PostPosted: Jul Tue 09, 2019 10:12 pm 
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Location: Beaver Falls, PA. USA
Have you considered the Loktal 7F8? It was used in some early FM and television sets, by Colonial and Philco.

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 Post subject: Re: octal equivelent to a 12AT7 tube?
PostPosted: Jul Sat 13, 2019 8:07 am 
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Joined: Sep Thu 23, 2010 6:37 am
Posts: 12229
Location: Powell River BC Canada
E1148

Cheap $6. tube depot. And just think how strange it would look. Good to 300 mHz.

Did I mention I have 100 of them. :D (to be crushed as a coffin liner)
Attachment:
E 1148  cheap as dirt.JPG
E 1148 cheap as dirt.JPG [ 50.79 KiB | Viewed 1004 times ]

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