NOS tubes: my collection, test results and ?s

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by ajbergren, Jan 18, 2008.

  1. ajbergren

    ajbergren Member

    Messages:
    144
    Joined:
    Jun 8, 2006
    Location:
    Edmonton, Alberta, Canada
    I recently obtained a tube tester and numerous NOS tubes.
    I've tested the preamp tubes with this:
    [​IMG]


    Here are the results:

    3 Chinese 12AX7s:
    Tube 1: Plate current (V1: 0.95 mA, V2: 1.1 mA); Transconductance (V1: 2.5 mA/V, V2: 3.05 mA/V)
    Tube 2: Plate current (V1: 0.95 mA, V2: 1.25 mA); Transconductance (V1: 2.45 mA/V, V2: 3.8 mA/V)
    Tube 3: Plate current (V1: 1.25 mA, V2: 1.3 mA); Transconductance (V1: 2.8 mA/V, V2: 2.65 mA/V)

    1 Sovtek 12AX7/USSR (I have two others to test yet):
    Tube 1: Plate current (V1: 2.15 mA, V2: 1.95 mA); Transconductance (V1: 2.63 mA/V, V2: 2.58 mA/V)

    2 JAN Philips 12AX7WA/USA:
    Tube 1: Plate current (V1: 1.35 mA, V2: 1.05 mA); Transconductance (V1: 2.35 mA/V, V2: 2.20 mA/V), some cathode/heater deflection
    Tube 2: Plate current (V1: 0.8 mA, V2: 1.55 mA); Transconductance (V1: 2.10 mA/V, V2: 2.50 mA/V)

    1 Beckman labeled 12AX7 (GE etch) USA:
    Tube 1: Plate current (V1: 0.5 mA, V2: 0.72 mA); Transconductance (V1: 1 mA/V, V2: 1.5 mA/V), V1 was in intermediate region

    4 Mullard 12AX7/ECC82, various labels (Gr. Britain):
    [​IMG]

    Tube 1: Plate current (V1: 1.33 mA, V2: 1.35 mA); Transconductance (V1: 2.45 mA/V, V2: 2.3 mA/V)
    Tube 2: Plate current (V1: 1.50 mA, V2: 1.50 mA); Transconductance (V1: 2.6 mA/V, V2: 2.5 mA/V)
    Tube 3: Plate current (V1: 1.38 mA, V2: 1.28 mA); Transconductance (V1: 2.42 mA/V, V2: 2.4 mA/V)
    Tube 4: Plate current (V1: 1.65 mA, V2: 1.39 mA); Transconductance (V1: 2.40 mA/V, V2: 2.1 mA/V)

    2 GE boxed Marconi Radiotron 12AX7 (Canada):
    [​IMG]

    Tube 1: Plate current (V1: 0.45 mA, V2: 0.60 mA); Transconductance (V1: 1.85 mA/V, V2: 2.05 mA/V), tested in green “good” range
    Tube 2: Plate current (V1: 0.60 mA, V2: 0.83 mA); Transconductance (V1: 2.02 mA/V, V2: 2.19 mA/V), tested in green “good” range


    1 GE 12AX7 (Used, from 1979 Fender Champ):
    Tube 1: Plate current (V1: 0.87 mA, V2: 0.80 mA); Transconductance (V1: 2.2 mA/V, V2: 2.15 mA/V), tested in green “good” range

    2 GE 5751 ***** (USA):
    [​IMG]
    Tube 1: Plate current (V1: 1.3 mA, V2: 1.65 mA); Transconductance (V1: 2.0 mA/V, V2: 2.0 mA/V), 1.0 mA plate current is spec.
    Tube 2: Plate current (V1: 1.4 mA, V2: 1.35 mA); Transconductance (V1: 1.81 mA/V, V2: 1.81 mA/V) , 1.0 mA plate current is spec., 1.2 TC spec.

    Sylvania, GE etch label 12AY7 (USA):
    Tube 1: Plate current (V1: 2.6 mA, V2: 2.3 mA); Transconductance (V1: 2.25 mA/V, V2: 1.95 mA/V), 3.0 mA plate current is spec., 1.75 TC spec.

    GE 12AY7 ***** (USA):
    Tube 1: Plate current (V1: 2.9 mA, V2: 2.7 mA); Transconductance (V1: 2.25 mA/V, V2: 2.1 mA/V) , 3.0 mA plate current is spec., 1.75 TC spec.

    [FONT=&quot]Tube 2: Plate current (V1: 2.95 mA, V2: 2.95 mA); Transconductance (V1: 2.25 mA/V, V2: 2.25 mA/V) , 3.0 mA plate current is spec., 1.75 TC spec.



    Now, I also obtained several other tubes:
    Siemens boxed, Made in England 5AR4:

    [​IMG]
    Is this a Mullard?

    A pair of Sylvania 6L6GC:

    [​IMG]
    Are these tall bottle? They seem quite a bit taller than other 6L6GCs (including the RCA below)...

    Various Rectifiers:
    [​IMG]
    [​IMG]

    Including a Sylvania Made In Holland 5Y3:
    [​IMG]
    Is this a common tube? Who is the original maker?

    RCA 6L6GC Blackplate:roll:

    [​IMG]


    And several others. See:
    http://s272.photobucket.com/albums/jj187/ajbergren/
    for more pictures.


    I notice that many of the tubes have letters on them. Are these date codes? For example, the 5AR4 has F32 then B*** (can't read it). Also, the Sylvania 6L6GCs say PV on them. There are many other examples. Two of the Mullard 12AX7s say I63 and B7E3. I can't find codes on the other two, but I've noticed they can be hard to read. The plate structure is identical on all four.

    Also, regarding the test results, it is typical for GE 12AX7s to give such low plate current? All the ones I tested gave low plate current, even when they were from various sources. The 5751s and 12AY7s that were GE seemed right on spec.

    Is there any way to ID years using these numbers? Any other info on these would be appreciated. Basically, I'm just having fun learning the ropes of NOS tubes. I find it quite fascinating!!

    Thanks all, and I hope everyone enjoys the pics (I know I always like looking at these when others post them)!!
    [/FONT]
     
  2. lp144

    lp144 Supporting Member

    Messages:
    425
    Joined:
    Dec 22, 2005
    Location:
    San Francisco Bay Area
    That's tubular!


    >I notice that many of the tubes have letters on them. Are these date codes? For example, the 5AR4 has F32 then B*** (can't read it).

    Mullard date codes are etched near the bottom of the glass near the pins.

    >Two of the Mullard 12AX7s say I63 and B7E3. I can't find codes on the other two, but I've noticed they can be hard to read. The plate structure is >identical on all four.

    Look at the tubes in strong light and slowly rotate...the light will glare on the date codes...some are very hard to see.


    >Is there any way to ID years using these numbers? Any other info on these would be appreciated. Basically, I'm just having fun learning the ropes of >NOS tubes. I find it quite fascinating!!

    try...
    tubemongerlib.com
    kcanostubes.com
    audiotubes.com
     
  3. teleman1

    teleman1 Supporting Member

    Messages:
    13,461
    Joined:
    Mar 17, 2006
    Location:
    AIRY ZONY
    THe 5y3 is a rectifier,used in champs. IT is probably a rebranded amperex.
     
  4. Blue Strat

    Blue Strat Member

    Messages:
    30,036
    Joined:
    Aug 2, 2002
    Location:
    Sterling, VA (not far from Washington DC)
    FYI, that "Sylvania" 6L6GC is actually the cheapo Russian 6L6GC that you don't see much of any more since better models are available.
     
  5. rockon1

    rockon1 Member

    Messages:
    11,468
    Joined:
    Aug 12, 2005
    Location:
    Stamford CT
    B= Blackburn England
    7=1967
    E= may
    3= third week

    Heres a good link . Bob

    http://www.tube-classics.de/TC/Tubes/Valvo/Phlipscode.htm

    .
     
  6. ajbergren

    ajbergren Member

    Messages:
    144
    Joined:
    Jun 8, 2006
    Location:
    Edmonton, Alberta, Canada
    Thanks all! Those links are absolute awesome! I spent a few hours browsing each!

    I need to learn how to test and match power tubes with the AVO, so it looks like I'll be doing some reading!!

    This is exactly the information I need!! Thanks!

    I am overwhelmed right now, as I have found another 2 dozen tubes or so, and I need to spend some time with the AVO (it is already a slow tester, and I am a new user)!
     
  7. Timbre Wolf

    Timbre Wolf GoldMember Supporter Gold Supporting Member

    Messages:
    8,817
    Joined:
    Oct 14, 2005
    Location:
    Berkeley, CA
    There is a similar Russian tube that is sometimes labled as "6L6G," and look a little like old Visseaux construction. I bought one once, just for the hell of it. What a waste!

    - Thom
     

Share This Page