G811a Triode Driver

[darkspeed]

Waiting on parts.....    To build a 160w hv hf supply from four g811a triodes


UPDATE:
Built most of it today.. Still waiting on the 10a variac,  fans,  and I need to build the control plate and screen that will enclose it.

2 CH @ 160w  filtered DC supply.

Grids can be driven from a signal generator or from a feedback loop.

Added two banks of RF capacitors so the primary of each triode can be tuned






If it works well I may build a bigger one from a 833A tube

[darkspeed]

1 - 2000v microwave oven transformer

2 - 6.3v 20a triad filament transformers

2 - 4 pin tube bases

2 - triode caps

2 - G-811 Russian Triodes

3 - 1.8nf 10kv capacitors

2 - 30ohm 20w resistors

1 - 5kohm 50w resistor

1 - 20kv vacuum variable capacitor

1 - 140v variac

1 - BNC connector

3 - 4000v 1uf filter capacitor

4 - 16kv diode

1 - 20a RF filter

3 - cutting boards

4 - WC float rods

1 - 3kvdc panel meter

1 - filament power switch

1 - mot power switch

1 - 120v pc fan

[darkspeed]

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[darkspeed]

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[Grumpy]

Nice cutting boards 

Why do the two resistors have coils wrapped around them?

[stprue]

Very nice build Darkspeed....I bet those vacume cap's wern't cheap!

[darkspeed]

Nice cutting boards 

Why do the two resistors have coils wrapped around them?

Thanks guys..

G. - the resistor / inductor act as a choke if the tube tries to become a spark gap  normally its a bad idea to use metal case resistors in this function but i paint them with corona dope so they are ok.

[Grumpy]

Thanks guys..

G. - the resistor / inductor act as a choke if the tube tries to become a spark gap  normally its a bad idea to use metal case resistors in this function but i paint them with corona dope so they are ok.

why wrap the coil around the resistor?  does it have ferromagnetic material in it?

[darkspeed]

why wrap the coil around the resistor?  does it have ferromagnetic material in it?

Honestly its an old tube thing.. RF builders have been doing that forever, i think it just makes a handy former..

[Grumpy]

Honestly its an old tube thing.. RF builders have been doing that forever, i think it just makes a handy former..

yes, but you only have a few turns, not hundreds.  Hi freakin' freq choke.

[darkspeed]

yes, but you only have a few turns, not hundreds.  Hi freakin' freq choke.

Yes! correct! when a triode arcs out the RF between the internal parts is in the very high MHZ...

If you over drive the plate voltage it can arc out and the choke will most of the time save the tube from failure

The 811 is good to 30mhz but the grid will free resonate at 100mhz so choking above 30mhz is a safe bet.