NOS tubes: my collection, test results and ?s

ajbergren

Member
Messages
201
I recently obtained a tube tester and numerous NOS tubes.
I've tested the preamp tubes with this:
Originals011.jpg



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):
NOStubes020.jpg


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):
NOStubes003.jpg


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):
NOStubes002.jpg

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:

NOStubes011.jpg

Is this a Mullard?

A pair of Sylvania 6L6GC:

NOStubes009.jpg

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

Various Rectifiers:
NOStubes015.jpg

NOStubes014.jpg


Including a Sylvania Made In Holland 5Y3:
NOStubes.jpg

Is this a common tube? Who is the original maker?

RCA 6L6GC Blackplate:roll:

NOStubes017.jpg



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]
 

lp144

Silver Supporting Member
Messages
556
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
 

teleman1

Silver Supporting Member
Messages
16,031
THe 5y3 is a rectifier,used in champs. IT is probably a rebranded amperex.
 

Blue Strat

Member
Messages
30,694
FYI, that "Sylvania" 6L6GC is actually the cheapo Russian 6L6GC that you don't see much of any more since better models are available.
 

ajbergren

Member
Messages
201
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!!

FYI, that "Sylvania" 6L6GC is actually the cheapo Russian 6L6GC that you don't see much of any more since better models are available.

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)!
 

Timbre Wolf

>thermionic<
Platinum Supporting Member
Messages
12,134
FYI, that "Sylvania" 6L6GC is actually the cheapo Russian 6L6GC that you don't see much of any more since better models are available.
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
 




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