From: Philip Nasadowski
Subject: Re: Digital divide by ten, 1949 style
Date: Sun, 15 Sep 2002 17:32:02 -0400
Organization: Biker/metalhead from hell!!!
NNTP-Posting-Date: 15 Sep 2002 21:35:20 GMT
X-Harley: '99 FXDWG
User-Agent: MT-NewsWatcher/3.1 (PPC)
In article ,
John Woodgate wrote:
> Yes, the plain number, without 'G' or 'GT' mean 'metal tube'. They had a
> thin glass envelope inside the metal can.
Actually, they didn't. At least not the ones I've pulled aprt. The
metal can *is* the envelope. There's a glass 'button' base at the
bottom though. The use of which likely did more to allow HF operation
than the 'metal' tube. The metal's for sheilding. BTW, the 6L6 was
orrigionally a mteal tube, and thus, pin one connected to the envelope.
A few amp makers forgot this and used pin one as an HV tie point, not
realizing that insertion of a metal 6L6 would put the envelope at
whatever voltage was at pin 1...
> The 6SN7 was the single-ended version.
Somehow, the 6SN7 hung on forever too. I think it was made domestically
into the 70's, and you can still get new foreign ones...
> 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.
Typical US AC/DC set is: 35W4, 50C5, 12BA6, 12BE7, 12AV7. 35Z5, 50L6,
12SK7, 12SA7, 12SQ7 for octal types. This would be post WWII.
> Not for TVs; pentagrid mixers don't do too well even at 50 MHz.
Typical US TV set had a tridoe oscilator and a pentode mixer, with an RF
stage of some sort ahead of it, and pentode IF stages (3).
> 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.
Interesting. In the US, the 'Compactron' base in the early 60's was an
attempt at getting rid of plate caps, and allowing dual pentodes, etc.
Many TV sets used them - in horizontal output service, a few had the
plate connection through the base (between 2 unused pins), but most sets
retained the conventional top cap connection. BTW - there were 7 and 9
pin miniatures with top caps too, normally for high voltage rectifier
service, though the 1B3 hung on in B&W TV sets an amazingly long time
(into the 70's maybe).
GE origionally showed off a 3 tube AM Compactron radio set, that was
actually as small as transistor tabletops of the era, but never made it.
Interestingly, GE made the Portacolor TV sets from 1965 to 1980, with
almost no circuit changes whatsoever. I believe it's the last widely
produced consumer electronic device with tubes in it (saving for the CRT
and magnetron, I mean tubes as small signal devices)
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