From: John Woodgate
Subject: Re: Digital divide by ten, 1949 style
Date: Mon, 16 Sep 2002 16:46:36 +0100
Organization: JMWA Electronics Consultancy
Reply-To: John Woodgate
NNTP-Posting-Date: Mon, 16 Sep 2002 18:09:11 +0000 (UTC)
X-Newsreader: Turnpike (32) Version 4.01 <5Z8C9wtxbnpWyFnyfFzqmVF739>
I read in sci.electronics.design that Chuck Simmons
wrote (in <3D850A3C.31381AD5@webaccess.net>)
about 'Digital divide by ten, 1949 style', on Sun, 15 Sep 2002:
>I repaired hundreds of radios from about 1957 until I actually started
>working at a radio station in 1963. I never saw a 6K8 in a radio at all.
>The All American Five had the 12BE6 mixer, the 12BA6 pentode IF, the
>12AV6 diode triode detector-AGC-audio amplifier, the 50C5 beam pentode
>audio power amplifier and the 35W4 rectifier.
Those B7G-based tubes are from much later.
>There was an octal tube
>complement used in an identical design from the late 1930s until about
>1948 when the list above became absolutely universal in low cost AM
>radios. The schematic is here:
I don't believe you had 12BE6 and 12BA6 in 1948.
>I can't remember ever seeing a 6K8 in an AM broadcast radio and I fixed
>radios that were antiques even in 1957 (TRF recievers that predated the
>superheterodyne) - I was able to do that because my father had a lot of
>tubes he had collected during the 1930s and 1940s.
Well, you wouldn't see a 6K8 in a TRF, would you!
>I did run across an oddity I had forgotten about. There was an AA5
>variant that used a rectifier with a 117 volt filament. The other tubes
>had 1 volt filaments. These were rare indeed.
There are six 117 V heater types listed in my book. 117L7, 117 M7, 117N7
and 117P7 were output pentodes plus rectifier, with 117 V 90 mA heater.
117Z3 was a B7G rectifier with a 40 mA heater. 117Z4 and 117Z6 were
also rectifiers, with 40 mA and 75 mA heaters respectively. Apart from
the 117Z3, they were all GT types.
Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk
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