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Old June 2nd 19, 08:29 PM posted to sci.electronics.repair
Jeff Liebermann Jeff Liebermann is offline
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Default Another old-timer tube/valve question

On Sun, 02 Jun 2019 12:56:58 -0400, Pat
wrote:

On Sun, 2 Jun 2019 15:57:22 -0000 (UTC), Cursitor Doom
wrote:
What are the typical average/maximum operating temperatures of a full
wave rectifying tube/valve? Is it normal for them to become too hot to
touch after only a minute or two?
I'm talking specifically about the 5Y3GT in this context.


Vacuum Tubes (Valves) work by heating the cathode to "boil off"
electrons. The 5Y3 has a 5v filament that draws 2 Amps. So that's 10
watts even without any current flowing in the plate circuit. So, yes,
I would expect it to get hot quickly.


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.


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