Metropoulos Forum

Hey guys!

Today I spent the evening testing and labeling nearly all the old tubes that I have at home... I turned on my Precise 111 Tube tester and took a pen to write all the labels. Yo guys can imagine the image... I think my neighbors think that I'm some kind of terrorist building bombs or something

I took some photos that I'd like to share with the only people that understand me

My Brimars, killer tone in plexis


My RFT's... easy and cheap to get in Europe, great in 2203 type amps.


My Miniwatts (phillips Holland):


RCA's (including one black plates )


A lot of General Electric, both short and long plates:


Some Sylvanias:


In addition, I have 5 Mullards and 4 Tungsrams, but they are in my amps rockin'

I know that is a little collection, but I'm proud

If you have some comments, feel free to say whatever you want

ooops, I forgot, the family shot:

You almost have as much as I do, but most of my tubes are NOS. I don't keep any tubes that are under 1600Gm.

1600?

What type of measurement are you using?
The NEW value of a 12ax7 is 1150 micro ohms according to the datasheet. Most of mines are around 1250-1350, so it's arond a 120% of the average new value. In fact, new production tubes straight from the box use to give me results of 1250.

What method are you using for testing?

Because some of these tubes were tested before by a pro-tech and those results make sense with my measurements. The ones that were labeled by him as "strong nos" give me around 1400-1500, and the ones simply labeled as "nos" give me 1250aprox.

The minimum value, according my tube tester manual is 800, so I think that 1200 means a tube plenty of life.

Thank you for comment

Carbia wrote:1600?

What type of measurement are you using?
The NEW value of a 12ax7 is 1150 micro ohms according to the datasheet. Most of mines are around 1250-1350, so it's arond a 120% of the average new value. In fact, new production tubes straight from the box use to give me results of 1250.

What method are you using for testing?

Because some of these tubes were tested before by a pro-tech and those results make sense with my measurements. The ones that were labeled by him as "strong nos" give me around 1400-1500, and the ones simply labeled as "nos" give me 1250aprox.

The minimum value, according my tube tester manual is 800, so I think that 1200 means a tube plenty of life.

Thank you for comment

1600 Transconductance "Gm" That's what you check for Not Micro Ohms. look at any data sheet. Also Amplification "Gain" 100 should be 100 or above 92. 1600 and above = NOS

sorry, but you're wrong, the transconductance is the same as Gm and it is measured in micro ohms (uohm) or mA/V that is the same.

Usually, datasheets provides the Gm=transconductance at 100v on the plate and at 250v, with -1v bias and -2v bias.
Look:
http://www.drtube.com/datasheets/12ax7-sylvania1955.pdf
http://www.drtube.com/datasheets/12ax7-rca1962.pdf

But not all tube-testers apply these exact voltages, so you have to trust the manual of your tube tester. Mine says that minimum acceptable is 800, so 1300 is a great reading.
In fact, if I do an Emission test, also known as GAIN test, most of my tubes are above 95%

But as I said, it depends on the tube-tester.
Hickock says that the minimun is 875, other brands says that is 1100, it depends on the voltages applied.

Carbia wrote:sorry, but you're wrong, the

transconductance is the same as Gm

and it is measured in micro ohms (uohm) or mA/V that is the same.

Usually, datasheets provides the Gm=transconductance at 100v on the plate and at 250v, with -1v bias and -2v bias.
Look:
http://www.drtube.com/datasheets/12ax7-sylvania1955.pdf
http://www.drtube.com/datasheets/12ax7-rca1962.pdf

But not all tube-testers apply these exact voltages, so you have to trust the manual of your tube tester. Mine says that minimum acceptable is 800, so 1300 is a great reading.
In fact, if I do an Emission test, also known as GAIN test, most of my tubes are above 95%

But as I said, it depends on the tube-tester.
Hickock says that the minimun is 875, other brands says that is 1100, it depends on the voltages applied.

Halo that's what I said. I've been through this before. The old tube testers suck. A lot of ebay sellers hate me because they can't scam me. I also do an audio test for shits and giggles, but over all my numbers are correct.

I have/had a couple of great sounding GE labeled Mullards I61 or I63. Can't remember but they sounded great.

axeman wrote: Halo that's what I said. I've been through this before. The old tube testers suck. A lot of ebay sellers hate me because they can't scam me. I also do an audio test for shits and giggles, but over all my numbers are correct.

No, you didn't say that.

You say that I have to look for Gm instead of micro ohms, when it's the same.

I do a test too after testing them, 'cause sometimes a tube that tested good, have noise or some issues.

But the best is the final phrase: "but over all my numbers are correct".
And you say that without any explanation. You are right and no matters what the rest of the world think about it. Good for you.

My Brimars, killer tone in plexis

Together with Tungsram; my favorite.

Yeah, Tunsgrams are great too, but I prefer them in Hiwatt. In Marshalls my choice is Brimar or Mullard. Although Sylvania runs well too, but with different character, but nice anyway.

Carbia wrote:Yeah, Tunsgrams are great too, but I prefer them in Hiwatt

Might have to negotiate on that then!!

Maybe

Both types, Mullards/Brimars and Tungsrams runs very good in Hiwatts, but Tungsrams have that tightness and headroom that makes Hiwatts sound BIG.

Had an I61 Mullard from '61, and every amp I stuck that in V1 was like a boost. Pisses me off that I let it go with a JTM-45 I sold on Ebay. Accidentally. had it in there jamming and boxed it up when it sold.
Nice tube collection Dude!
Old Bugle Boys kill as well, love them in the Marshalls.