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The 6SN7 Identification Guide - Page 2

post #16 of 72
National Union (NU) gray glass 6SN7GT with rectangular top mica is the same with RCA grey glass which is the same as RCA VT-231
post #17 of 72
Thread Starter 
Quote:
Originally Posted by chat7 View Post
National Union (NU) gray glass 6SN7GT with rectangular top mica is the same with RCA grey glass which is the same as RCA VT-231
Look again -

There is no rectangular mica on a true NU grey glass. It is round. The mica spacers are also square, in contrast to the rectangular ones on both RCA variations.

When you have enough experience with tubes you will realise that labels can mean nothing - I've seen tubes that were clearly RCA labeled NU.
post #18 of 72

RCA 6SN7GTA

Just a quick couple of questions on the RCA 6SN7GTA.

I've got a single pair of these tubes which actually seem like a very nice 6SN7 variant. They have two side getters, directly opposite each other and at right angles to the plates (meaning, you can look at the flat side of the plates, but the gap between the plates if you're looking at the edge is obscured by the getters). Why two getters?

Also, what's up with this tube? Seems like RCA made 6SN7GTs for quite a while, made the GTAs for a very short time, and then moved right into GTBs. Is my perception correct?

Thanks,

Stuart
post #19 of 72
Thread Starter 
Quote:
Originally Posted by sturob View Post
I've got a single pair of these tubes which actually seem like a very nice 6SN7 variant. They have two side getters, directly opposite each other and at right angles to the plates (meaning, you can look at the flat side of the plates, but the gap between the plates if you're looking at the edge is obscured by the getters). Why two getters?
the question should be - why not?

Actually, no one outside of the engineers/designers behind that tube will likely know the answer to that question. I suppose the best answer for now would be: because they can.

Quote:
Originally Posted by sturob View Post
Ilso, what's up with this tube? Seems like RCA made 6SN7GTs for quite a while, made the GTAs for a very short time, and then moved right into GTBs. Is my perception correct?
Yep - 100% correct. GTAs were never very popular and were quickly superceded by the better-rated GTB. My understanding is that GTAs took time to succeed the GT type (much like how leaded petrol was phased out in favour of unleaded), and by the time the phaseout of GT was complete, GTBs were already on the market. Kinda like how we all jumped from CD to VCD while leaving LD on the wayside.
post #20 of 72
Why not indeed. They look like a lot of work; I guess I'm not surprised the GTBs succeeded them so quickly. There seem to be a ton of Sylvania GTAs, but not so many RCA GTAs. Doing both of those getters, flashing both sides, blah blah, lots of extra time/expense if it's not "needed."

They are a nice tube/valve, though.

Stuart
post #21 of 72
Thread Starter 
Quote:
Originally Posted by sturob View Post
Why not indeed. They look like a lot of work; I guess I'm not surprised the GTBs succeeded them so quickly. There seem to be a ton of Sylvania GTAs, but not so many RCA GTAs. Doing both of those getters, flashing both sides, blah blah, lots of extra time/expense if it's not "needed."

They are a nice tube/valve, though.

Stuart
I just realised that the tube you mentioned is not in my 'guide' - it would be great if you could drop me an email. If you would like to, please send it to the address listed in the first post. Thanks!
post #22 of 72
adhoc, this thread is really a great asset to this forum and anyone else interested in the 6SN7GT. Well done, thanks!

I was wondering about your observations of the different filament alternatives, i.e. the 8SN7GT and 12SN7GT. Have you seen or heard of if these differ in construction to the 6,3V versions, besides the heater parts?

Interestingly, the Tungsram CV1988’s I have, have grey coating to the top mica, brown (micanol?) bases and black, staggered, ladder-ridged-flat-plates. The micas are racetrack formed, and the top one, with spikes at the round parts, touching the glass. Barely visible bottom getter. They are also stamped 6SN7GT (note not GTY).

The base is without print, but the envelope is marked with the KB/T stamp with arrow, which means government ordered, approved, made to specification K1001 or K1006 and manufactured by Tungsram, Tottenham.

I’ll email you about the GEC B 65.
post #23 of 72
It is my understanding, from my readings, that the RCA 6sn7's with the side getters, are actually made by GE. Do you know is that true?

- augustwest
post #24 of 72
Thread Starter 
Quote:
Originally Posted by augustwest View Post
It is my understanding, from my readings, that the RCA 6sn7's with the side getters, are actually made by GE. Do you know is that true?

- augustwest
I am not certain as I only own 2 GTAs and both are GE. Have a look at the EIA codes on the tube - a 3 digit number should indicate the tube's 'true' manufacturer.

312 is Sylvania
188 is GE
274 is RCA

and so on...
post #25 of 72
hey, no triangle plate Sylvania 6sn7.

actually, no triangle plate anything!

but they exist.
post #26 of 72
Thread Starter 
Quote:
Originally Posted by nikongod View Post
hey, no triangle plate Sylvania 6sn7.

actually, no triangle plate anything!

but they exist.
Got a photo?

I'm thinking that you might be thinking of 'angled T plates' as 'triangle plates'.
post #27 of 72
adhoc -

I have a 6sn7 tube that I am hoping you might help me identify? It is a brown base, medium bottle with trianlular black plates. The only indentifing markings on it are "6sn7 / Tele - Rad" in small point type face.

- augustwest
post #28 of 72
Thread Starter 
Quote:
Originally Posted by augustwest View Post
adhoc -

I have a 6sn7 tube that I am hoping you might help me identify? It is a brown base, medium bottle with trianlular black plates. The only indentifing markings on it are "6sn7 / Tele - Rad" in small point type face.

- augustwest
A picture says a thousand words - send a picture to the email address in the first post.
post #29 of 72
Thread Starter 
Quote:
Originally Posted by augustwest View Post
adhoc -

I have a 6sn7 tube that I am hoping you might help me identify? It is a brown base, medium bottle with trianlular black plates. The only indentifing markings on it are "6sn7 / Tele - Rad" in small point type face.

- augustwest
Hope ya got my email.

If the spam filter ate it, it's almost certainly a Tungsol WGT or WGTA.
post #30 of 72
"If the spam filter ate it, it's almost certainly a Tungsol WGT or WGTA."

Thanks!

- augustwest
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