The 6SN7 Identification Guide

[rnros]

Yes, vertical read on the paint code. Yes, also on the '54 date for both base paint and top glass etch.
 
And, I know you like these. Don't overlook the GTBs of the mid to late '50s.

 

[ThurstonX]

  Yes, vertical read on the paint code. Yes, also on the '54 date for both base paint and top glass etch.
 
And, I know you like these. Don't overlook the GTBs of the mid to late '50s.

 
Thanks, Bob
 
I've got at least two pairs of GTBs, plus the two Fotons still to roll.

 

[rnros]

Sure. And, I know, above all else, you are thorough!
 
Later I will send you some info on a 6C8G that I think is as good (or almost?) as the better 6SN7s I've heard in the Lyr.
300mA heater so can be used in the Lyr2, or the MJ2 if you're thinking of going there.

 

[Kryl0071]

Hi
Do you have any ideas about data of year prodaction Sylvania 6sn7gtb?
I can read codes
31
12
26
Also I have got RCA 6sn7gtb red print with code 63-35
Same question.

 

[Oskari]

Hi
Do you have any ideas about data of year prodaction Sylvania 6sn7gtb?
I can read codes
31
12
26

The way to read that is 312 126 where 312 is Sylvania and 126 is a YWW date. Since it's a GTB, 1951 is not possible. I'd bet on 1961. 26 could be the week, but it might mean second quarter as well.

Also I have got RCA 6sn7gtb red print with code 63-35
Same question.

That should be YY-WW.

 

[Kryl0071]

Thanks a lot!!!

 

[RoundRound]

Guys,
So just to clarify, if I have 6SN7 NOS tubes that are buzzing when used, there's no chance it will improve over time and the tubes are basically useless for audio?
Is there a point cleaning the contact pins? And if so with what?
 
Thank you,

 

[whirlwind]

  Guys,
So just to clarify, if I have 6SN7 NOS tubes that are buzzing when used, there's no chance it will improve over time and the tubes are basically useless for audio?
Is there a point cleaning the contact pins? And if so with what?
 
Thank you,

Yes, they could improve...if these are older tubes, remember they may have been sitting on a shelf some where for years....give them some time to settle in.
 
If the pins seem dirty, use some fine grit sand paper on them.

 

[RoundRound]

Thanks mate,
How long will you give the tubes to improve?
 
Also what about cleaning the pins with 95% alcohol?

 

[ThurstonX]

  Thanks mate,
How long will you give the tubes to improve?
 
Also what about cleaning the pins with 95% alcohol?

 
Assuming you mean isopropyl alcohol, that's fine.  I use 99% isopropyl + wood shaft cotton swabs, followed by DeoxIT Gold (from the Vacuum Tube Survival Kit).  I almost always clean some oxidation off the pins.  6SN7GTs usually take two swabs per tube, due to the pin size, I reckon.  Good luck with the crackle and buzz.  If they don't clear up after 100 hours, I'd be surprised if they ever do.  I have a pair of Siemens CCas I got for super cheap, one of which had that problem.  I gave it a few whacks with a pencil, which settled it down, ran it for a couple days, and the problem did not resurface.  YMMV.

 

[RoundRound]

   
Assuming you mean isopropyl alcohol, that's fine.  I use 99% isopropyl + wood shaft cotton swabs, followed by DeoxIT Gold (from the Vacuum Tube Survival Kit).  I almost always clean some oxidation off the pins.  6SN7GTs usually take two swabs per tube, due to the pin size, I reckon.  Good luck with the crackle and buzz.  If they don't clear up after 100 hours, I'd be surprised if they ever do.  I have a pair of Siemens CCas I got for super cheap, one of which had that problem.  I gave it a few whacks with a pencil, which settled it down, ran it for a couple days, and the problem did not resurface.  YMMV.

Thanks mate!
What do you mean whack it with a pencil??

 

[ThurstonX]

Thanks mate!
What do you mean whack it with a pencil??

 
OK, maybe "whack" is too strong a word.  Gently tap, tap, rap... in my experience that affects the crackle/buzz, and sometimes clears it up.  Sometimes the crackle/buzz will return.  Whaddaya gonna do.  Obviously you don't want to hit it so hard as to break the glass, but tube glass is pretty thick, at compared to a light bulb.  So, if you hear the crackle/buzz, give the glass a light tap and listen for a difference.  If it's only one tube, you'll need to know which tube feeds which channel (e.g., in the Schiit Lyr, Left is front, Right is rear).  Anyway, easy enough to tell when you start tapping.  Since this type of crackle/buzz is apparent without any audio playing, it's best if there is none.  Makes it easier to hear the effect.

 

[RoundRound]

   
OK, maybe "whack" is too strong a word.  Gently tap, tap, rap... in my experience that affects the crackle/buzz, and sometimes clears it up.  Sometimes the crackle/buzz will return.  Whaddaya gonna do.  Obviously you don't want to hit it so hard as to break the glass, but tube glass is pretty thick, at compared to a light bulb.  So, if you hear the crackle/buzz, give the glass a light tap and listen for a difference.  If it's only one tube, you'll need to know which tube feeds which channel (e.g., in the Schiit Lyr, Left is front, Right is rear).  Anyway, easy enough to tell when you start tapping.  Since this type of crackle/buzz is apparent without any audio playing, it's best if there is none.  Makes it easier to hear the effect.

Thank you,
I'll give it a go!

 

[ThurstonX]

Just had to post this.  It's a world gone mad: http://www.ebay.com/itm/2-Tung-Sol-JAN-CTL-6SN7GT-round-plate-tubes-test-strong-balanced-tube-6SN7-amp/142285377649
 
OTOH, I snagged a pair of black-glass KEN-RADs for $61 

 

[Kryl0071]

Hi
RCA 6SN7GTB data code ML. Any ideas about Year of made?