6v6 and 6v6GT

[Enzo]

A quick look through my closest RCA copy shows all the power tubes as pentodes in the pinout drawings. 6L6, 6BQ5, 6V6, 6550, EL34, etc. I have seen data sheets with the little deflector symbols for beam elements, but I don;t see them in my RCA. And that leads me to conclude that I cannot rely upon the pinout diagram to tell me if a tube is a beam tube or a pentode. The text description does that.

My suspicion is that in terms of the schematics, it doesn;t matter what type tube it is, and perhaps they felt it less confusing - potentially - if the element after the screen was just always drawn as a grid. SOme other data sheet issuers may have felt differently.

And miltown, while current catalogs may offer a "6V6", unless it is a NOS offering, it won;t be a true 6V6. The metal tubes are pretty rare. I have seen darn few of those in my career. A lot fewer than I have metal 6L6s. SO if you are selecting from currently produced tubes, like EH, and JJ, and SOvtek, etc, then making a distinction between 6V6 and 6V6GT is pointless. Let's just say that current use of 6V6 is an informal use of the type name.

[miltown]

Yeah I have only seen them as glass envelope tubes. That is why I really didn't understand the distinction between 6V6 and GT. I had read I think at National valve that the heater warm up time was different between the two that is why I posted that earlier. I would like to bust one open much like Tubeswell had stated. I'm picking up some tubes in Chicago this weekend that a friend had purchased from a TV repair place going out of business years ago. He said the whole bag cost him 5 bucks. There is probably 50 tubes in the bag. I know I saw the 6BQ , I didn't see any 6v6's but I also just looked into the bag when he showed it to me a few weeks ago. I grabbed a couple of boxes 6BD6,6FQ7 and some others.

[ThermionicScott]

Once in a while, you'll see a tube diagram with [ ] brackets to indicate the beam-forming plates, but most of the time they drew it as a grid, which is admittedly confusing. You can tell whether a tube is a beam tetrode or a pentode by counting the number of grid support rods sticking up through the top mica. Pentodes will have 6 and beam tetrodes will have 4, with some flat metal tips twisted over to anchor the beam-forming plates -- same as is done for the plate. Tremo has taken some good pics of 6V6 pins here: 6V6 comparisons in Tubes Forum

Dubious Russian/Chinese suppliers aside, I would bet a lot of money that no true pentode has been marketed as a 6V6. Even if they got the transconductance close to a real one, the curves would be a lot different.

- Scott

[Enzo]

It pays to have the RCA book handy. The 6V6 paragraph starts out, "Metal type 6V6 and glass octal type 6V6GTA..."

Same thing over at 6L6, "Metal type 6L6 and glass octal type 6L6GC..."


The heater warm up time is characterized for the 6V6GTA, but not for the 6V6. They may or may not be different, the metal tube is simply not spec'd.

[Diablo]

Some old 6V6 tubes of various versions.

[JoeM]

Your collection?

[Diablo]

Your collection?

Yes, they're good used pulls that I got from a friend. He gave my 8 beer case boxes full of tubes to sort through. There are some very odd and prehistoric tubes too - I think some date back to the 1930s.

[ThermionicScott]

Neat! I won an eBay auction a while back for about 30 misc used 6V6GT's -- I've got a picture somewhere. They all work fine, and the variation in construction is fascinating. It turns out that "real" Tung-Sol 6V6GT's used a round plate like you'd expect in a 6K6!

- Scott