6v6 and 6v6GT

[miltown]

Sorry I'm a newbie here. I have a question about the 6V6 and 6V6GT version. Is the only difference between them filament warm up time? So would it be ok to swap them.

paul

[dodona]

GT means glass tube.

[miltown]

Thank you!!

paul

[Steve Conner]

6V6 @ The National Valve Museum

[dodona]

thanks to Steve:

6V6 (steel envelope): 6V6 @ The National Valve Museum
6V6GT (glass): 6V6G @ The National Valve Museum

[miltown]

Thanks for the link .

[tubeswell]

In addition the 6V6GT is a beam tetrode rated for 12W plate dissipation, whereas the 6V6GTA is a pentode and can be rated up to 14W http://scottbecker.net/tube/sheets/135/6/6V6GTA.pdf

[miltown]

Yeah I have been looking at the datasheets from National. I wanted to order some 6v6's but I would see the GT or just 6v6 listed and wasn't sure. Thanks for posting I've read a few of your other posts and they are always informative.

[ThermionicScott]

GT is a reference to the compact "bantam" tube envelope originally developed by Hytron in the late 1930's.

It's not true that 6V6/6V6G are 12W tubes and 6V6GTA are 14W tubes. What happened is that the industry switched from the "design center" to the "design maximum" ratings system for 6V6's around the time 6V6GTA's where introduced, and most of the data sheets you find online are early examples. I have in front of me a 1960 tube manual from RCA that lists 6V6 (yes, the metal ones) and 6V6GT at 14W plate, 350V max. I am skeptical that the guts of the tube changed during this period, except for the heater.

- Scott

P.S. The 6V6 never changed to a pentode (implying the presence of a suppressor grid), either. It's unfortunate that GE put "beam pentode" in the linked datasheet, because there is no such thing! 6V6's were "beam tetrodes" or "beam power tubes" the whole way through.

[Jazz P Bass]

The "Beam Power Tube" is actually a hybrid between the tetrode & the pentode.
The steering beams are supressor grids in a way.

[ThermionicScott]

The "Beam Power Tube" is actually a hybrid between the tetrode & the pentode.
The steering beams are supressor grids in a way.

Beam-forming plates serve much the same role as suppressor grids, but that doesn't make them the same thing.

Most tube-minded people know how these tubes work, it's just the nomenclature that irks me at times. I mainly wanted to make sure it was understood that 6V6's were never reworked as true pentodes. (Why would they? That's the EL84/6BQ5's job...)

- Scott

[miltown]

I have a couple of those 6BQ5's I haven't checked out the data on them didn't know they were pentodes. I'm still learning here as you can tell from the number of posts I have.

[tubeswell]

Well the GE and Tung-Sol 6V6GTA datasheets have schematics of a pentodes on them (suppressor grid'n'all).

And I didn't say they were 14W, I said they can be rated for 14W (so there) ;-b

[miltown]

Is the suppressor grid called the getter also? The little halo in the tube.

[tubeswell]

The suppressor grid (in the schematic in the datasheet - and who knows whether it actually exists in the real world? I must pull apart an RCA 6V6GTA and see for myself) is connected to the cathode internally. Suppressor grids in pentodes are physically situated between the screen and the plate - so they are in the part of the apparatus that is enclosed by the plate. The suppressor grid is there to stop any electrons that bounce off the plate from going further back the wrong way. Whereas the getter(s) are elsewhere in the bottle (but outside of the plate structure). A getter is only used once when the bottle is first made, to de-gas the 'vacuum' inside the envelope (or if you, as a mad scientist, want to re-activate the getter in order re-vitalise a flagging tube by giving it a quick zap in a microwave oven).

This begs the question of what's actually inside a JJ6V6S. Beam tetrode or beam pentode? The datasheet says its a pentode but...