[SBE] Certification note

[k7cr]

Mark -

Great story about a tube that I have spent a great deal of
time with- Mind if we reproduce this in the our local
chapter newsletter?

(Wondering if you should have mentioned the KT88
and EL34's ?)

Clay Freinwald
----- Original Message ----- 
From: "Mark Heller" <wgbw at lsol.net>
To: "sbe member discussion mail list" <sbe at sbe.org>
Sent: Thursday, November 15, 2007 6:12 AM
Subject: Re: [SBE] Certification note



> The 6L6 is a descendant of the "Harries Valve" developed by British 

> engineer

> J. Owen Harries and marketed by the Hivac Co. Ltd. in 1935. Harries is

> believed to be the first engineer to discover the "critical distance"

> effect, which maximized the efficiency of a power tetrode, by positioning

> its anode at a distance which is a specific multiple of the screen

> grid-cathode distance. This design also minimized interference of 

> secondary

> emission electrons dislodged from the anode.

>

> EMI engineers Cabot Bull and Sidney Rodda improved the Harries design with 

> a

> pair of beam plates, connected to the cathode, which directed the electron

> streams into two narrow areas and also acted like a suppressor grid to

> absorb some secondary electrons. The beam design was also undertaken to

> avoid the patents which the giant Philips firm held on power pentodes in

> Europe. Because this overall design eliminated the "tetrode kink" in the

> lower parts of the tetrode's voltage-current characteristic curves, which

> sometimes caused tetrode amplifiers to become unstable, MOV marketed this

> tube family under the sobriquet "KT", meaning "kinkless tetrode".

>

> Because MOV's engineers did not feel the kinkless tetrode could be

> successfully mass-produced, they licensed the design to RCA. This proved 

> to

> be a poor business decision on MOV's part. RCA subsequently had enormous

> success with the 6L6. It replaced the use of power triodes in 

> public-address

> amplifiers almost overnight. So many applications were found for the 6L6

> that a complete list would be impossible to assemble. MOV introduced their

> version, the KT66, a year later.

>

>

> The 6L6 Pinout, metal versions had the shell connected to pin 1RCA's first

> version had a metal-canister shell rather than glass - being one of the

> early octal base tubes, most of which were marketed as having metal 

> shells.

> Later versions, including the 6L6G, 6L6GA, 6L6GB, 5881, 5932, 7027, and 

> the

> final version 6L6GC had glass envelopes, which made radiation cooling of 

> the

> anode easier. The voltage and power rating of the 6L6 series was gradually

> pushed upwards by adding features such as a micanol base, thicker plates,

> thicker grid wires, grid cooling fins, and special ultra-black plate

> coatings. The original metal version was rated for 19 watts dissipation,

> while the later 6L6GC is usually rated for 30 watts.

>

>

> ----- Original Message ----- 

> From: "John E. Beck" <wb0rxl at yahoo.com>

> To: "sbe member discussion mail list" <sbe at sbe.org>

> Sent: Thursday, November 15, 2007 7:49 AM

> Subject: Re: [SBE] Certification note

>

>

>> Is "B" the correct answer?

>>

>> Come on guys - don't leave me hanging!

>>

>> John E. Beck

>> WB0RXL

>>

>> ----- Original Message ----

>> From: "A9xw at cs.com" <A9xw at cs.com>

>> To: sbe at sbe.org

>> Sent: Tuesday, November 13, 2007 5:45:36 PM

>> Subject: Re: [SBE] Certification note

>>

>> In a message dated 11/13/2007 4:54:15 PM Central Standard Time,

> wgbw at lsol.net

>> writes:

>> >

>> > and, I'm so old, I remember when we were asked to present possible

>> > questions for the test... maximum ten questions per chapter!

>>

>> I bet they were good ones too!

>>

>> A 6L6GB is used as:

>>

>>       A. video modulator for high level TV modulation

>>       B. audio amplifier power output

>>       C. as a low distortion amplifier using screen grid feedback

>>       D. all of the above

>>       E. none of the above

>> _______________________________________________

>> SBE mailing list

>> To unsubscribe, go to http://seven.pairlist.net/mailman/options/sbe

>> _______________________________________________

>> SBE at sbe.org

>> http://seven.pairlist.net/mailman/listinfo/sbe

>>

>>

>>

> ____________________________________________________________________________

> ________

>> Get easy, one-click access to your favorites.

>> Make Yahoo! your homepage.

>> http://www.yahoo.com/r/hs

>> _______________________________________________

>> SBE mailing list

>> To unsubscribe, go to http://seven.pairlist.net/mailman/options/sbe

>> _______________________________________________

>> SBE at sbe.org

>> http://seven.pairlist.net/mailman/listinfo/sbe

>

> _______________________________________________

> SBE mailing list

> To unsubscribe, go to http://seven.pairlist.net/mailman/options/sbe

> _______________________________________________

> SBE at sbe.org

> http://seven.pairlist.net/mailman/listinfo/sbe

>

>