Couple of (newbie) tube questions...

[JoshK]

Hi all,

I'll cut to the chase.

Is a 5y3 and a 5y3gt equivalent electrically?

What is a "getter"? Or do you have a link that explains the anatomy of a tube?

TIA, cheers,
Josh

[Johan Potgieter]

Hi Josh

Quick reply while I am browsing: A 5Y3 is a directly heated full wave rectifier and is electronically the same as a 5Y3GT; only the glass envelope is different. But nothing is ever simple these days! (...and this is the main purpose of my quick reply). I have recently encountered a Sovtek 5Y3GT - with an indirectly heated cathode!

The original 5Y3 is directly heated, i.e. the filament itself is used as the source of electrons. The problem with a filament is to get enough "emitter" surface for large currents; one cannot make the filament ribbon too thick. Thus indirectly heated tubes were developed where the "emitter" is a tube which can have a far larger area, heated by a filament placed inside the tube (called a cathode). The latter is a more efficient device and have largely superceded the directly heated types.

Point is that the Russians have no business to call a different tube by the same number, even though the suffix may differ. (I am afraid the Soviet is known to be very free with type designations.) In this respect your 5Y3GT might not be the same as the original 5Y3 - it is easily visible though.

A getter is a circular thin metal "gutter" placed inside all vacuum tubes, filled with a chemical that will ignite when heated. When this "burns" it combines with whatever remnants of oxygen might have remained behind after the vacuum process, thus eliminating all traces of oxygen. After ignition it gets deposited as a shiny blotch easily visible inside a glass tube surface. The getter is in the form of a ring so that it can be heated by magnetic induction from outside, to a temperature that will ignite the chemical.

[Eli Duttman]

What is a "getter"?

A getter is a mirror like flashing of highly reactive metal (Barium/Cesium/Rubidium) on the inside of the envelope. The getter chemically ties up any Oxygen that remains after evacuation. It gets gas, hence its name.

Is a 5y3 and a 5y3gt equivalent electrically?

More or less. There are minor ratings differences between the various "flavors" of the tube, but most of the time they are not critical. Check the data sheets for specific details.

[Eli Duttman]

I have recently encountered a Sovtek 5Y3GT - with an indirectly heated cathode!

They really should call that tube a 5Y3WGTB/6087. 5Y3 variants with cathode sleeves have been around for quite some time. Perhaps the best of the lot is the Bendix Red Bank 6106.

[Johan Potgieter]

Thanks Eli; now I know. Have not used them for decades.

[JoshK]

Thanks guys.

[Sir Trefor]

Originally posted by JoshK

What is a "getter"? Or do you have a link that explains the anatomy of a tube?

Do these diagrams help?


Sorry, they came out smaller than I expected them to be.