[David222]

These are the RCA codes I found online

Z - 1936
U - 1937
T - 1938
X - 1939
R - 1940
Y - 1941
S - 1942
K - 1943
H - 1944
V - 1945
F - 1946

1 - JAN-FEB
2 - MAR-APR
3 - MAY-JUN
4 - JUL-AUG
5 - SEP-OCT
6 - NOV-DEC

E stands for OEM

I find this --> DOC useful for RCA date codes.

 

[bcowen]

I just got these last week for $72 after someone pointed them out to me on this thread, and I'm really enjoying them so far. They have the best/largest soundstage of anything I've tried yet, good bass and midrange.

6SN7GT RCA radio amplifier JAN CRC audio vacuum tubes 2 valves tested 6SN7GTB

Very nice! And a great price for them too.

What are the dates on them? Should be on the other side of the tube from what's shown in the photo. GTA's and GTB's weren't introduced until 1950, so what you likely have are just GT's rather than GTB's.

 

[rawheadjim]

They have a square with S and C at the top two corners, and a triangle inside the square with a 71 below it. Not sure what that means by the date document?

 

[bcowen]

They have a square with S and C at the top two corners, and a triangle inside the square with a 71 below it. Not sure what that means by the date document?

That's a military stamp and doesn't indicate the manufacturing date. Should be a 3 or 4 digit code on the base somewhere, unless it rubbed off.

 

[TLO]

I find this --> DOC useful for RCA date codes.

Yes, that is the document we found the date codes from.

 

[TLO]

They have a square with S and C at the top two corners, and a triangle inside the square with a 71 below it. Not sure what that means by the date document?

That is the code for the U.S. Signal Corps, not date. Those tubes are RCA 6SN7 GT from the 40's, same as RCA VT-231 for the U.S. military. Later RCA 6SN7 GTB will have clear glass with side flash getter. If I remember correctly, RCA 6SN7 GTB were made by GE.

 

[ostewart]

Just won this for cheap, wonder if it's any good. No actual test readings sadly, but worth a punt for the price.

 

[rawheadjim]

The only other numbers I can find anywhere on the base are 9-35 on both of them.

 

[bcowen]

The only other numbers I can find anywhere on the base are 9-35 on both of them.

Then if I'm reading the info correctly, those would be the 35th week of 1949. I will stand corrected if anyone has better info.

 

[mayurs]

Are these RCAs the same as CBS Hytron or RCA Red/Brown base 5692s? I did some googling but could not ID these tubes accurately.

 

[Ripper2860]

Then if I'm reading the info correctly, those would be the 35th week of 1949. I will stand corrected if anyone has better info.

GTBs were not introduced until 1954**, I believe. If it is a GTB that date code 9 would stand for 1959.

** corrected.

 

[TLO]

GTBs were not introduced until 1945, I believe. If it is a GTB that date code 9 would stand for 1959.

I believe GTB started around mid 50's and not 40's. GTA is from around 1950-54. BTW, those are 40's RCA 6SN7 GT with smoke glass, just before they moved to GTA with clear glass. @bcowen is right, they should be 1949.

 

[Ripper2860]

Typo -- I meant introduced about 1954 (not 1945). I hate typing on a phone screen.

And that's what I also get for skimming as opposed to reading. GTs vs GTB.

 

[TLO]

Are these RCAs the same as CBS Hytron or RCA Red/Brown base 5692s? I did some googling but could not ID these tubes accurately.

Those are RCA 5692 labeled as RCA 6SN7 GT. RCA is printed on the base...
These are CBS 5692.

 

[bcowen]

GTBs were not introduced until 1954**, I believe. If it is a GTB that date code 9 would stand for 1959.

** corrected.

The 3-numeral code went from '46 to '56, and in '56 the code for the year went to two alpha digits. That's why I went with 1949 instead of 1959.