Simple vintage? Chinese TV

[jr_tech]

A friend, while looking for a schematic for a CTC-5A found an interesting schematic for a very simple early Chinese TRF electrostatic TV. He speculates that the tuned circuit in the screen grid of the first audio tube may help detect FM audio. Note that the TV uses line powered HV and that the power transformer provides no isolation (except for the heaters). Also note the solid state rectifiers, which may indicate that the set is *not really* very early. I'm guessing that the 135 in the CRT designation indicates 135 mm or about 5 inch. "Madman" Muntz would be proud!

http://www.neazoi.gr/technology/vttv/6Tube_TV.GIF

from: http://www.neazoi.gr/

Anybody here with knowledge/speculation about this set or its design?

jr

[egrand]

Heck, they're probably still making them!

I don't know for sure, but I'm willing to bet China didn't start getting tv until late 50's, and even then probably for the elite. I don't think China has ever been known for making safety issues a priority in their product design.

[Sandy G]

Yeah, w/3 BILLION of 'em, they can afford to lose a few here & there... Kinda sucks if YOU'RE one of the one or 2, though...

[wa2ise]

Originally Posted by jr_tech

He speculates that the tuned circuit in the screen grid of the first audio tube may help detect FM audio.

That's a quadrature FM detector circuit, commonly used in later American tube TV sets. Friend of mine, David K., who grew up in Shanghai in the 50s-60s-70s once told me that he built a TV set by hand, using an electrostatic deflection CRT like one from an oscilloscope (presumably white phosphor). He went back to Shanghai and lost contact with him, maybe this was the circuit he used... Looking at that schematic a little closer, I don't see the horizontal section.

[jr_tech]

Originally Posted by wa2ise

Looking at that schematic a little closer, I don't see the horizontal section.

G5A, 1/2 6N1 (6N7?)?

jr

[danny]

Hi The curcuit dont faze me there were some uk sets in the fifties that had a transformer with heaters isolated and ht from the primary but then most uk sets shassis is connected to one side of the mains and most these are on a two pin reversable plug.
And 240v supply and if you were realy lucky you could be on dc mains. this set is typical for a fifties home made electrostatic tv. as for the valves the good old 6sn7 could be used. Danny

[David Roper]

The all-time minimalist champ was a Soviet one-tube set. Two tubes if you count the CRT of course, which was a small magnetically-deflected tube. IIRC the other tube was a hexode-triode with the latter section dedicated to audio output and all sorts of clever multiplexing going on to accomplish the rest. There were a number of crystal diodes used but zero transistors. Really. The last time I looked for the schematic I couldn't find it; hopefully somebody else bookmarked or saved it.