Great work so far!
Please measure the filament voltage at the socket. The cable and connectors cause significant voltage drop, which explains the lower current draw.

What a beautiful valve. Can't wait to hear it on 3615 (here's hoping!).

What a beauty! Look forward to seeing what you do with it.

Very impressive and an enjoyable watch, thanks.

I ´ve  got some of  the smaller GU-81 Valve right beside the test jig. I made  an audio amp with 2 of them . 1500Wrms with 2500V anode volts an 650V  at the screens in class B2. Input power before clipping, 5,2kVA runs on 230/400V three phase . I made the amp abt 10 yrs ago. Sounds amazing with a handfull jBL control 12s.
The GU-81 is a russian  version of the RS-384  made by Telefunken in 1936. Those valves a rare to come by, but the GU-81 is available in numbers . Its much more difficult to get the socket for the valve.

Looks like the large 1 they have on Radio Caroline.

Amazing..!

Very impressive.....so prob owned by the BBC once.

See please Russian GM-100 triode. 1kW   48cm * 21cm   5kV

Use a microwave oven transformer. You get at least kV type output voltages, find them on side of road plus they have hv caps and diode for v doubling.

1000W anode dissipation. Could produce 2kW carrier in class C!

Great stuff!!!!!!!
Any updates on the availability of the triode control boards yet mate?

Love that Tube, I have ones of Similar Age and Size like the Siemens GRI Triode. About the 14A Current, I see on the VoltMeter 9.9V out but for sure you have quite some Voltage drop due to the rather thin wires to the Filament. Set the PSU to have 10V Measuring directly at the Filament Pins of the Tube, this will compensate the Voltage drop of the Leads and you probably come closer to the 16A. Great Video.

Btw, any change to get the schematics, of the Switchmode PSU you use (I watched your 2020 Video about it) including the Coil/Transformer data ? Thankyou.
Cheers, Konstantin

Meanwhile the World Service on AM is discontinued because the UK- for all its much-vaunted expertise can't rebuild mid-century valves.

How can valves be transmitted?  Do you have a matter transporter?

Don't forget the DC blocking capacitor between the plate choke and the pi tuning! 😉 Otherwise, brilliant! 😃👌

10 volts at 16 amps.....thats 160 Watts...filament power....doing nothing!!!

Does this lamp emit soft X-rays? )