Hello..my first TV

[old_coot88]

V2, whatever tube that is, gets filtered positive DC on its heater, supplied by that circiut. The little selenuim is a full-wave rectifier. If replacing with Si diodes, you may need to bump the value of that 1 ohm resistor up a bit to avoid overvolting V2's heater.

[jr_tech]

Scratching my head here... why is V2 heater also connected to the upper leg of the AC heater supply?

What is V2 and what is its function?

jr

[Donj]

Coot,
V2 is the oscillator tube on the tuner... pretty sensitive area to be messing with if not necessary I expect. Maybe I best leave it be for now.

[Donj]

jr,
Tube is a 12at7. Split filament maybe?

[jr_tech]

Originally Posted by Donj

jr,
Tube is a 12at7. Split filament maybe?

Yes, so indeed, the heater for 1/2 of the tube runs on AC and the heater for the other 1/2 runs on DC.... I don’t believe I have seen that before. Curious!

jr

[old_coot88]

Yes, the whole 12AT7, 'AU7, 'AX7 family have split heaters with pin 9 as common. So they can be run in series on 12V, or in parallel on 6V. But V2 in your set evidently has 6V DC on one and 6V AC on the other.

(Edit) jr_tech nailed it first. I never seen that arrangement before either. Just a SWAG, but since V2a is the tuner's oscillator, the DC heater scheme is to minimize 25 cycle "FM-ing" of the oscillator.