The Reference 6SN7 Thread
Jul 20, 2019 at 5:59 AM Post #691 of 7,806

Roasty

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Jul 20, 2019 at 7:23 AM Post #692 of 7,806

attmci

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Jul 20, 2019 at 11:46 PM Post #694 of 7,806

JKDJedi

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Sylvania 6SN7GT. Were they ONLY made between 1946-1953 as this website states? https://www.tubeworld.com/6sn7.htm#sylgt I'm trying to figure out the which decade these tubes are--> 2019-07-20 17.13.21.png
My understanding is the first number is (top to bottom) last digit of year then next two are numbers of the week.

ANd Are these the Bad Boys?? Dated 1952.

Bad boys.jpg
bad boys 2.jpg bad boys 3.jpg
 
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Jul 21, 2019 at 2:34 AM Post #695 of 7,806

Ripper2860

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Top pic: 852 looks like a 1952 (8th month) Chrome Dome. The tube on the right w/ what seems to be a 313 code is a bit of a mystery. 313 looks like a MFG code, but Sylvania's MFG code is 312. Not sure if that's a factory error, some other type of code (factory code?) or another MFG relabeled by Sylvania. I cannot find a reference to a 313 MFG code in any of my docs, so it's a bit of a mystery to me.

Bottom pic: They seem to have all the required characteristics of Bad Boys and 1952 certainly fall within the range. 6SN7GTA came out about 1954
 
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Jul 21, 2019 at 12:47 PM Post #696 of 7,806

JKDJedi

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Top pic: 852 looks like a 1952 (8th month) Chrome Dome. The tube on the right w/ what seems to be a 313 code is a bit of a mystery. 313 looks like a MFG code, but Sylvania's MFG code is 312. Not sure if that's a factory error, some other type of code (factory code?) or another MFG relabeled by Sylvania. I cannot find a reference to a 313 MFG code in any of my docs, so it's a bit of a mystery to me.

Bottom pic: They seem to have all the required characteristics of Bad Boys and 1952 certainly fall within the range. 6SN7GTA came out about 1954
Thanks for your input, a member here brought it to my attention (Sennfan83261) some documentation that states the Slyvania 6SN7GT stopped production in 1954 http://vintagetubeservices.com/wp-content/uploads/2018/03/Octal_Tubes_March_2018.pdf So if the codes read like stated on the first page of this thread end of year (last digit) on top and last two numbers the week of that year, these tubes would be, or read as, 1948 52nd week and 1953 13th week. Thats what my thought s are now if there's any validation the document is correct. And yes I'm hoping these are the real deal "Good Boys" just a little nervous about the getter flash being a liitle dull, usually a sign of leakage. Won these off an auction on Ebay and the price is a liitle to good to believe.. so yeah, a crap shot at best.
Edit: Update, turns out this dealer doesn't know what he's doing, or maybe he does, apparently these tubes got sold without his knowledge and he offered me something different, of course I denied the offer. Be careful out there guys.
 
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Jul 24, 2019 at 6:28 PM Post #698 of 7,806

cddc

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Those two should be disposed according to the readings.
C-top 5998 is very close to 421A if you can find one.

I agree the $13ish pair has a very low reading...I personally won't bid on them...waste of money and shipping fee.

On the other hand, the ones on screenshot I think is way overpriced.
 
Jul 24, 2019 at 6:29 PM Post #699 of 7,806

ScubaMan2017

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Jul 24, 2019 at 7:57 PM Post #701 of 7,806

cddc

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Hey guys the special notes on the first page of this thread has me a little worried about the 6SN7GTA tubes I have coming in.. are they amp specific and/or will they work in place of a regular 6SN7 tube?

6SN7GTA*
- 'Upgrade' of 6SN7GT, max 450Volt Ua, 5W per system and 7.5W total. Hence tube better fulfills special requirements for TV sweep applications, like higher peak power and better impulse capabilities.
If your amp is designed around this tube, you MAY NOT be able to substitute in other 6SN7 versions due to the higher ratings for this tube – check with your manufacturer.

Can use a GTA in place of a regular 6SN7, will likely last slightly longer due to the higher ratings. Using a regular 6SN7 in place of a GTA where the circuit has been designed around the GTA might have some undesired effects though.


Nice Q&A.

I was once concerned about 6SN7 GTA/B's as well, because their 450V plate voltage is much higher than the 300V GT ones.

Glad to hear they are okay in circuits designed for 6SN7 GT's, but can someone let me know if GTA/B's are biased correctly in a circuit designed for GT's? Do GTA/B's and GT's have the same B+ voltage (i.e. 450V v.s. 300V is just rating instead of desired B+ voltage)?
 
Jul 28, 2019 at 7:36 PM Post #702 of 7,806

JKDJedi

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Nice Q&A.

I was once concerned about 6SN7 GTA/B's as well, because their 450V plate voltage is much higher than the 300V GT ones.

Glad to hear they are okay in circuits designed for 6SN7 GT's, but can someone let me know if GTA/B's are biased correctly in a circuit designed for GT's? Do GTA/B's and GT's have the same B+ voltage (i.e. 450V v.s. 300V is just rating instead of desired B+ voltage)?


Copy n Pasted from the Universe Somewhere...

"This is the later improved version, and the improvements were primarily geared toward the TV chassis designers who demanded more max. plate wattage and voltage, where vertical circuits can put up to 1500 volt pulses at 7 watts on the plates. For hi-fi audio use, these improvements are meaningless. These are fine tubes, nonetheless. Most are found in the short glass envelope, but some brands like Raytheon used the Tall Boy style. Sylvania made tubes have the triangular plates mounted lower, and set at angles to each other, although some of the very earliest examples of the GTA types still used the dull blackplates facing each other. RCA used the flat black plates "sideways" to each other, and GE used the grey plates parallel to each other. The Sylvania types in demand have a large top getter patch. The earliest Sylvania GTA types have a green label and heavy top getter flashing extending down the sides of the tube. Watch for the very rare "Tall Boy" Sylvania 6SN7GTA, one of the few tall glass tubes made by Sylvania for this tube type, said to rival the military types in sound quality. The early GTB types are similar, but most have a yellow or red label, with some rare first production run tubes still out there with the 1940s green label. Watch for these tubes, made by Sylvania for other brands like Zenith, Philco, and Motorola. They are currently bargain priced and are the same fine tube as those with the Sylvania label! The versions from the 1960s have the getter just covering the top of the tube. All of these have the same black triangular plates and are excellent tubes. The GE types have a side getter and large parallel grey plates, and the RCA used both bottom or side getter. Some side and bottom getter types have 2 getter patches on top, right above the plates. This often happened during the factory gettering process with 6SN7 types that did not have top getters. It is not a sign of use, as the spots are usually bright silver and visible on tubes still sealed in the box. Most other vintage USA brands you find will have been made by these three vendors, and will be one of the above variations, regardless of brand on the label. A few were made with brown micanol bases, the RCA types being very dark brown, the GE types being a lighter, marbled brown. The brown micanol bases are most often found in military tubes, as they resist heat, moisture, and fungus/mildew growth. It was not uncommon, however, for manufacturers to repackage unsold military surplus tubes in "civilian" boxes and sell them to the general public. Many audiophiles prefer either the Sylvania chrome tops, the RCA, or the GE side getter over any others, even over the military or redbase types. These are all a great bargain now, and are sure to be rare and expensive tomorrow".


Not sure if this answered your question though, :D Anywho, just don't slap a 6SN7 tube in an amp designed for these TV tubes. but your ok to use these tv tubes on a 6SN7 amp. Like mentioned on page 1 of this cool thread.
 
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Jul 28, 2019 at 8:01 PM Post #703 of 7,806

JKDJedi

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Found a nice surprise this weekend thats really blown me away with it's sonic quality, for the price. I've found these Sylvania made tubes (312) usually in pairs, on Ebay for really low prices, some sold individually for $49 and others for $21 a pair (anybody find these cheaper?). Copper posts, low getter flash past the base a bit and angled plates, a good digging up if your ever get the itch to grab something different.

ADMIRAL (312) 6SN7GT (1952)
2019-07-27 14.33.51-1.jpg
 
Jul 28, 2019 at 8:21 PM Post #704 of 7,806

cddc

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Found a nice surprise this weekend thats really blown me away with it's sonic quality, for the price. I've found these Sylvania made tubes (312) usually in pairs, on Ebay for really low prices, some sold individually for $49 and others for $21 a pair (anybody find these cheaper?). Copper posts, low getter flash past the base a bit and angled plates, a good digging up if your ever get the itch to grab something different.

ADMIRAL (312) 6SN7GT (1952)



Nice shot, buddy!

And thanks a lot for the cool paragraph above.
 
Jul 28, 2019 at 11:23 PM Post #705 of 7,806

OldSkool

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Found a nice surprise this weekend thats really blown me away with it's sonic quality, for the price. I've found these Sylvania made tubes (312) usually in pairs, on Ebay for really low prices, some sold individually for $49 and others for $21 a pair (anybody find these cheaper?). Copper posts, low getter flash past the base a bit and angled plates, a good digging up if your ever get the itch to grab something different.

ADMIRAL (312) 6SN7GT (1952)


Looks like a 3-hole 1952 Bad Boy to me. Nice score!
 

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