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    Building, troubleshooting and testing of these amplifiers should only be
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is the 12ax7 ever used on television sets?

I worked in TV repair from 1968 to 1973 and shopped the trash dump for tubes, transformers, and parts way back to the early 60's. I never saw a 12AX7 in a TV. 12AU7's yes, they were used for vertical sweep or horizontal oscillators in small black and white TV's. Ditto the 6CG7 and 6SN7.

The only place I found 12AX7's was HiFi or stereo sets, guitar amps, and occasionally an electronic organ, although most of them used 12AU7 or 6SN7.
 
Pinout compatible tubes you *may* find in a few TVs are 12AT7 or 12AV7 or 12AZ7 .
You won't have 12AX7 there because although they are perfectly fine for Audio, are lacking at RF and VHF frequencies, vital in TVs.

But if you get any of these, they are fine, only none has the same gain as a 12AX7 , which was optimized for Audio.

Gainfactor12XX7tubes_2.jpg~original


Sometimes I find a stash of TV tubes and design something specifically for them, but I need at least 100 or 200 units to make it worthwhile.

I once bought 1000 ECC189 and made a ton of excellent pedals with them, go figure.
 

Sorento

Member
2008-03-12 9:59 pm
in USA Zenith models "Brent, Mozart, Drew, Clark, Carroll, Archer" from 1953:
L1846E 'The Brent' Ch= 19L25 Television Zenith Radio Corp.;

all Emerson models 1956, e.g.:
1020H Ch= 120235-D Television Emerson Radio & Phonograph Cor

in England the Kolster-Brandes LFTxx models 1952:
LFT50 Television Kolster-Brandes Ltd. KB, ITT; Foots Cray; G

Bush, London, TV53 1955 (ECC83):
TV53 Television Bush Radio; London, build 1955, 2 pictures

in Italy models from Marelli 1954:
RV99 Television Marelli Radiomarelli; Sesto San Giovanni MI,

and some more, though all from the 1950's ... came out of fashion in the 60's ...
 
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I have seen PCC83's used in TV's. Same thing, different heater.
Frank
Sorry but not such a thing.

ECC83 as-is, with both filaments in parallel meets the 300mA demanded by series filaments strings in TVs so no need or justification to make a P version.

You might have seen others (such as PCC/ECC189) which demands somewhat higher filament power , so it's (roughly) E 6.3V 350mA or P 7V 300mA while ECC83 is both 6.3V and 300mA .