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6SN7 Tube Addicts

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  1. gibosi
    Not to my ears. :)
    Wes S likes this.
  2. Ripper2860
    Thank you. I found that document and I too could not find an ACS designation. This particular RCA is a D side getter holder, not a ring, so it looks like a mid-to-late '50s vintage.
  3. Wes S
  4. Ripper2860
    I hope I'm not being a pest. I really have tried looking up this info. via Google Search and also looked at the 6SN7 tube identification thread, but I just can't seem to locate the info. I seek. You fine folks have proven knowledgeable and helpful in my previous queries, so I thought I'd try here again.

    I got some tubes as part of a 4 tube lot -- two were Magnavox labeled / Sylvania made '53 Chrome Domes, and then there are two Sylvania 6SN7GTA's. I'm having the toughest time identifying the 6SN7GTA tubes vintage. The 2 are identical and as follows:

    Medium bottle
    Fully round mica spacers top/bottom w/ no spikes.
    Black angled T plates like : -/ \-
    Top chrome flashing (not fully extending like chrome dome -- just top 1/4)
    Yellow lettering Sylvania and logo on base
    6SN7 GTA is marked inside the stop sign emblem on the top of the tube glass envelope

    Now to where I need some help. Each tube has what I think is a 2 letter date code (BB for one and AF for the other). These are located on the base next to the S in triangle w/ lightning bolt logo. Anyone have a clue as to what the BB and AF codes mean? There are no other marking on the base other then the logo, Sylvania name, and the 2 letter codes. On the top of the glass envelope there is a I4B under the 6SN7GTA stop sign emblem on one tube envelope and B4B on the other. Are any of these date codes? I've found references to 2 letter date codes used on Sylvania and other tubes, but I have not found a table or info on how to decipher it for Sylvania. I'm really hoping to identify the year for these 2 tubes.

    Thanks in advance for any help!!
    Last edited: Jul 27, 2018
  5. gibosi
    I have yet to find a key to Sylvania's two-letter date codes. My best guess is that these are either shipping dates or warranty dates as they were applied just before the tube was packed and shipped.

    The three-digit etched codes located just below the hexagon are rather well-known and are likely manufacturing dates as the were applied in the factory. The first digit, a letter, is the month, the second digit, a number, is the year, and the third, a letter, is the factory.

    So I4B -> I is the 9th letter of the alphabet and represents the 9th month, September. 4 = 1954, and I have no idea which manufacturing plant B represents. And in the same fashion, B4B would be February, 1954 and factory B.

    Now, you will see the same date codes on 1940's Sylvania production (and 1930's production, as well), so a little detective work might be necessary. For example, we know that the 6SN7W was manufactured only the 1940's, so the etched code C5 is March, 1945. And we know that the 6SN7GTA was introduced in 1950, so these later tubes must have been manufactured in the 1950's.
    Last edited: Jul 27, 2018
    Wes S and Ripper2860 like this.
  6. Ripper2860
    Extremely helpful and detailed information. Thank you very much!!!
  7. Ripper2860
    I purchased a Philco (Sylvania) 6SN7GT with the below attributes:

    1. Bottom getter flashing extending 1/3 up the tube
    2. 3-hole black T-plates
    3. Top rectangular mica with 3- points per side
    4. Bottom rectangular mica.

    Looks just like an early 50's Sylvania GT, but has a weird date code of 5302. I've done some poking around and cannot really find a definitive answer -- there seems to be more RCA era date code info than Sylvie era. I'm guessing it's YEAR | WEEK or MONTH which would mean 1953 | week 2 or Feb), but I'm hoping you fine folks can confirm or provide more info.

    Thanks again!!!

  8. gibosi
    Around 1950, Philco began to use the EIA dating system, that is, YYWW, so it is likely that 5302 was the second week of 1953. And as 3-hole Sylvania "Bad Boys" were still being manufactured in 1953, that is likely what you have.
    Ripper2860 likes this.
  9. Ripper2860
    Once again -- your extensive knowledge of tubes saves the day!!

    Thank you!!!
  10. FindingNewSound
    Hello everyone, I know this might not be the appropriate place to ask, so I'm terribly sorry in advance, but does anyone have a spare Kenrad vt-231 black glass? I'm looking for one for my Lyr 3, would consider buying a pair too.
  11. Ripper2860
    Yes. It's me again and yes, I'm once again perplexed and have a question ...

    I purchased and received a Sylvania tube with 6SN7GT marked on the base and on the top of the glass envelope. The thing is, it looks like a short bottle 6SN7W. The plates look identical to short bottle W and it even has the single free standing support rod between the plates in addition to heavy top chrome flashing extending almost 1/2-way down. So my question is: Did Sylvania ever make a short bottle 6SN7W labelled as a 6SN7GT? (It's definitely not a Chrome Dome).

    As usual -- thanks!!!
  12. gibosi
    How about a pic? Especially the lettering on the base and the top to help with dating. Just off the top of my heard, it occurs to me that it might be a 1950's era 6SN7WGT
    Ripper2860 likes this.
  13. Ripper2860
    Will do as soon as I get home. Tube is a black base with racetrack mica which is different that the 50s WGT and WGTA tubes I've seen. I'll also take a closer look at top mica to see if it has an umbrella structure.
  14. Ripper2860
    Here you go @gibosi --

    Weird. Umbrella top mica and a 'W' on the top of the envelope, but a 6SN7GT in stop sign logo on the base. If I'm reading it correctly, date code looks like a 1946 /39th week. To me it's all the signs of a short bottle W except for the base stating 6SN7GT.

    Here are pics of just thew mystery GT / W ...


    6sn7GT-W-1.jpg 6sn7GT-W-2.jpg 6sn7GT-W-3.jpg 6sn7GT-W-4.jpg 6sn7GT-W-5.jpg 6sn7GT-W-6.jpg
    Last edited: Aug 15, 2018
  15. gibosi
    The etched info on top tells you all you need to know. It is indeed a short-bottle 6SN7W. The etching is part of the manufacturing process, The base was added later. Sometimes weeks, months or even years later. Thus, I trust the etching to be more accurate than the text and graphics on the base.

    I can't quite make out the numbers and letters etched below the hexagon, but the final "5" indicates 1945. You did well! Congratulations! :)
    MrPretty and Ripper2860 like this.
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