Tube ID

TEAforONE

I purchased these a couple of years ago,and like a goof,I never documented what they were. I’m almost certain they’re 12ax7’s. The markings are worn off,so I need the help of any tube gurus out there.

TEAforONE

After googling the interwebs, I think I solved the mystery. It looks like they are possibly RCA 5751 short black plates,halo getters. Any other guesses would be much appreciated.

pitdogg2

Any makings between the pins?
Yes at this point it's all guesses
Don't ask me how I know but Windex takes a stenciling right off tubes lickety-split

TEAforONE

pitdogg2 wrote: »

Any makings between the pins?
Yes at this point it's all guesses
Don't ask me how I know but Windex takes a stenciling right off tubes lickety-split

Let me check between the pins..........

TEAforONE

Not a thing between the pins.

pitdogg2

Rats.... Oh well worth a shot.

TEAforONE

I rolled these in my preamp today,and really like em. So of course I'd like to get something similar. Not as simple as one might think.
But seriously,looking at images on the web,I'm pretty sure of what the are .

F1nut

They do not look like RCA 5751's. They look like 12AX7's.

5751's are normally marked near the top in what looks like etched glass and that marking does not normally come off.

verb

Hey brother, can you take some close up pic's of the plates? Need a straight on view, and a side view. Hard to tell from the pics.

TEAforONE

F1nut wrote: »

They do not look like RCA 5751's. They look like 12AX7's.

5751's are normally marked near the top in what looks like etched glass and that marking does not normally come off.

F1nut, thanks for the id. I originally had thought 12ax7,but I had no idea about the etching. Again,thanks!

TEAforONE

verb wrote: »

Hey brother, can you take some close up pic's of the plates? Need a straight on view, and a side view. Hard to tell from the pics.

Hi verb, I won’t be able to take any pics until I get home from work. That should be about 4pm. Thanks!

heiney9

Pretty sure it's an American made tube. Short black plates aren't normal for a 12AX7. Any American black plate I've seen is a long plate and they are usually early tubes and as a rule don't have a halo on a post for a getter.

It could be a Canadian made version of an American tube possibly. They did that for some 12AX7's. I'll have to do some research this weekend, because a black short plate isn't common among the 12AX7. IIRC, the RCA 5751 has bump out plate not a flat plate.

H9

mhardy6647

I am so bad at this tube ephemera stuff!
It looks like every US (North American?!?) miniature/B9A base twin triode ever made to me -- well, except a "cleartop" 12AU7, I guess.



I.e., I got nothin'.

I am tempted to go upstairs and see what the 5751s in that little LRE amp up there look like.

TEAforONE

Here’s a couple more pics. Sorry,I don’t own a real camera.

pitdogg2

best picture of the bunch

TEAforONE

I've had these for at least a couple years. I spent yesterday rolling signal tubes in my pre,and these seem to have the secret sauce. If only I took the time to write down what they are. I'm kicking myself! Hopefully someone will recognize these.

verb

pitdogg2 wrote: »

best picture of the bunch

Yep. Those plates I've never seen!

TEAforONE

verb wrote: »

pitdogg2 wrote: »

best picture of the bunch

Yep. Those plates I've never seen!

Well,that's not encouraging!

mhardy6647

A suggestion that might (might?!?) be helpful. Try fogging the envelope glass with your breath. Sometimes, the residual runic inscriptions that once graced the tube can be read.

I do see some partially (mostly) eroded print on there -- don't I?

It might not help, but it's easy to try and only takes a moment.
I have occasionally managed to read otherwise invisible tube types printed on plinkers.
Plus, imagine the fun you'll have explaning it if a spouse or child comes into the room while you're blowing on a vacuum tube.

As an aside -- and y'all probably know this -- some tube manufacturers quite deliberately used very ephemeral print (as opposed to the etched markings) on their tubes -- to discourage unscrupulous repair persons from tube washing (literally) and selling an old tube 'pull' as a new tube.

Inconceivable.

TEAforONE

mhardy6647 wrote: »

A suggestion that might (might?!?) be helpful. Try fogging the envelope glass with your breath. Sometimes, the residual runic inscriptions that once graced the tube can be read.

I do see some partially (mostly) eroded print on there -- don't I?

It might not help, but it's easy to try and only takes a moment.
I have occasionally managed to read otherwise invisible tube types printed on plinkers.
Plus, imagine the fun you'll have explaning it if a spouse or child comes into the room while you're blowing on a vacuum tube.

As an aside -- and y'all probably know this -- some tube manufacturers quite deliberately used very ephemeral print (as opposed to the etched markings) on their tubes -- to discourage unscrupulous repair persons from tube washing (literally) and selling an old tube 'pull' as a new tube.

Inconceivable.

That seems like a GREAT idea. How on earth did you come up with that??? Will try that this evening!! And yes,that tube has some of the labeling still on it. It looks orangish red?
Is it possibly a GE tube? The thing that sucks,is eBay purchased search doesn't go back far enough.

verb

My guess is 12AT7. Sylvania construction, could be branded differently.

https://www.ebay.com/itm/SYLVANIA-12AT7-VINTAGE-TUBE-Black-Box-PLate-O-Getter-TV-7-Superb/254220204175?hash=item3b30b4788f:g:CIsAAOSw3udcza2a

verb

Green labeled Sylvania 12AT7's

mhardy6647

TEAforONE wrote: »

mhardy6647 wrote: »

A suggestion that might (might?!?) be helpful. Try fogging the envelope glass with your breath. Sometimes, the residual runic inscriptions that once graced the tube can be read.

I do see some partially (mostly) eroded print on there -- don't I?

It might not help, but it's easy to try and only takes a moment.
I have occasionally managed to read otherwise invisible tube types printed on plinkers.
Plus, imagine the fun you'll have explaning it if a spouse or child comes into the room while you're blowing on a vacuum tube.

As an aside -- and y'all probably know this -- some tube manufacturers quite deliberately used very ephemeral print (as opposed to the etched markings) on their tubes -- to discourage unscrupulous repair persons from tube washing (literally) and selling an old tube 'pull' as a new tube.

Inconceivable.

That seems like a GREAT idea. How on earth did you come up with that??? Will try that this evening!! And yes,that tube has some of the labeling still on it. It looks orangish red?
Is it possibly a GE tube? The thing that sucks,is eBay purchased search doesn't go back far enough.

I... I... read it on the internet.

Marky stuffs his hands into his pockets, looks down and shuffles his feet.

TEAforONE

And I’ll raise you... these have almost identical plates!

TEAforONE

verb wrote: »

My guess is 12AT7. Sylvania construction, could be branded differently.

https://www.ebay.com/itm/SYLVANIA-12AT7-VINTAGE-TUBE-Black-Box-PLate-O-Getter-TV-7-Superb/254220204175?hash=item3b30b4788f:g:CIsAAOSw3udcza2a

I think you're on to something,however the mystery tubes sound so different from the green label sylvania's. I'm very perplexed!!!

mhardy6647

Just musing I am, you know?



(that one on the right has a pretty funny looking seal on the exhaust tip, though, doesn't it?)

pitdogg2

most GE tubes had the glass laser etched with the brand it would NEVER go away.

Different era tubes from Sylvania had different color stenciling for and different plants could also have different sound signatures. I know for a fact that my 6sn7 Sylvania tubes had green, red, orange and blue labels all different years Blue was the last in the mid 70's and all you can see all a little bit differently made.

TEAforONE

I'm a relative nube with tubes,what is the seal on the exhaust tip?

verb

Hard to say really. From what I've learned, a lot of history out there where manufacturers made tubes for one another, others removed the original labeling and post applied their own, you name it.

Here's an example of the same tubes, Sylvania manufactured (except for double layer mica on top), labeled as Motorola.

TEAforONE

Thanks pitdogg2. That rules out GE. Process of elimination!

pitdogg2

verb wrote: »

Hard to say really. From what I've learned, a lot of history out there where manufacturers made tubes for one another, others removed the original labeling and post applied their own, you name it.

Here's an example of the same tubes, Sylvania manufactured (except for double layer mica on top), labeled as Motorola.

and yet that laser etching on the far right one screams to me GE. Except it is missing dots that GE also used.