On 2019-06-02 21:29, Jeff Liebermann wrote:
On Sun, 02 Jun 2019 12:56:58 -0400, Pat
wrote:

Ah yes, but you can get far more efficient Sovtek 5Y3GT tubes
(thermionic valves):
https://shop.ehx.com/item/5y3gt/tubes-vacuum-sovtek/
which features a filament that draws only 2mA +/- 0.2mA 5V or 10
milliwatts.

I like the description on the data sheet:
https://shop.ehx.com/catalog/addimages/5y3gt-sovtek.pdf
MINIATURE DOUBLE ANODE KENOTRON IN GLASS DESIGN
WITH OXIDE-COATED INDIRECTLY HEATED CATHODE INTENDED
FOR RECTIFICATION OF COMMERCIAL-FREQUENCY ALTERNATING
CURRENT.
That explains why one gets frequent commercials on TV sets that use
Sovtek 5Y3GT kenotrons.

Fortunately the datasheet really specifies 2A not 2mA. I was already
imagining a fake tube with 2x 1N4007 inside, and a 2mA LED to 'light up'
the cathode...

Arie