From: John Woodgate
Subject: Re: Digital divide by ten, 1949 style
Date: Sun, 15 Sep 2002 21:22:19 +0100
Organization: JMWA Electronics Consultancy
Reply-To: John Woodgate
NNTP-Posting-Date: Sun, 15 Sep 2002 20:49:50 +0000 (UTC)
X-Newsreader: Turnpike (32) Version 4.01 <5Z8C9wtxbnpWyFnyfFzqmVF739>
I read in sci.electronics.design that Chuck Simmons
wrote (in <3D84D4B3.50B511EF@webaccess.net>)
about 'Digital divide by ten, 1949 style', on Sun, 15 Sep 2002:
>The 6H6 dual triode dated from the late 1930s and was common in
>commercial and military equipment but the 5 tube radio of the era was
>inocent of the beast (if I recall, the 6H6 was a "metal" tube).
Yes, the plain number, without 'G' or 'GT' mean 'metal tube'. They had a
thin glass envelope inside the metal can. But the 6H6 was a double
diode. The earliest double triode appears to be the 6F8G - two 6J5
triodes in one envelope, with one grid on the top cap, The 6SN7 was the
>"MSI" came to tubes in the 1960s with the introduction of compactrons
>that might have two triodes and a pentode or some such.
No, double- and even triple-diode-triodes were around much earlier, as
well as triode-pentodes and triode-hexodes, like the 6K8 which was in
almost every US AC mains radio, and plenty of British ones, for many
years. Even some AC/DC products.
>I forget any of
>the numbers of these but in reality, these were like ASICs in that they
>really were optimized for particular applications in TV recievers. They
>had little impact on the traditional dual triodes like the 12AX7 and the
>12AU7 and the garden pentodes such as the 6AU6. Actually, some
>integration was not obvious. It seems to me the 6BE6 had 5 grids and was
>ideal as a mixer in superheterodyne recievers such as radios and TVs
Not for TVs; pentagrid mixers don't do too well even at 50 MHz.
>(there was a metal tube that was similar dating from the advent of the 5
Many, for sure; even the 1A6 2V filament tube, with a UX-6 base, was a
>Pin limitations on tubes were important in the 1920s and early 1930s, 6
>pins was about the limit.
Not so much in Europe. There was a UX-7 base in USA, but, although I
can't put exact dates on them, there were bases with up to at least 10
contacts in use in Europe before 1939. I have a double-tetrode tube LV4
listed, which I think was a Telefunken product, with a 10-contact base.
>A very common tube of the time, the 01-A had
>but 4 pins. Power tubes and some pentodes had the anode brought out
>through a contact at the top of the tube. The 417 and 723 local
>oscillator klystrons had the repellor on such a contact.
The 7193, the VHF/UHF version of the 6J5, had both grid and anode/plate
as top caps. They were sold off after WW2 in millions in Britain, for
very attractive prices (equivalent to 4p, but 4p was worth more then!).
>In the 1930s,
>the octal, 8 pin keyed base, came along. Later power tubes expanded the
>number of pins with the 826 dual power triode and even later the 829 and
>3E29 dual pentodes. In this era, miniature tubes had 7 or 9 pins (the
>classic 12AX7 and 12AU7, still available today in some variant, had 9
Well, not only power tubes. The EF50 r.f. pentode, which practically won
the electronic war (with the SP 41 and SP61), had a 9 pin base,
approximately octal-size. The SP41 and SP61 had Mazda Octal bases -
superficially like the International Octal but with a bigger key and a
larger spacing between pins 1 and 8.
Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk
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