Help identifying a Telefunken(?) tube...

[pyrotas]

Dear all,

I have found a very old tube, with noval socket, which I believe is a Telefunken. Markings are almost all gone, only the top triangle of the logo and the "EC" letters remain. At the bottom, a diamond shape is engraved in the glass. Plate is nowhere similar to twin triodes such as 12AU7 which seems to suggest me this is *not* a twin triode 🙂 I attach a zip with some pictures which could help.

Anyone knows what this tube is? Any help would be greatly appreciated!

Thanks in advance
Fabio

 

[singa]

and

Hi, As far as I can see it has two anode stuctures so it's should be a twin
triode.Most probably ECCXXXX and if you say it's not ECC82/12AU7
then a ECC83? 81? just test with meter for continuity of pin4,5 which is the
heater.

Just wire it up and test if it amplify a signal.Just don't exceed anode
voltage of 300V for signal tubes.😉 Singa.

 

[century tek]

I don't know if its my computer, but everytime I click on the attached file, my media player opens up. You can post pictures directly.

 

[rotaspec]

Looks identical to Telefunken ECF82 (==6U8) triode pentodes that I have here. Mine have a getter flash on the glass over the aperture in the pentode plate which makes it hard to see there, but the rest is identical.
The triode plate looks like it is bent and separating as well, but it might just be distortion in the pic.

Gary

 

[gullaz]

Looks very similar to an ecf82... must have an ecf82 tfk somewhere, I see if I can find it to compare with your pictures.

 

[costis_n]

it is an ECFxx for sure. A smaller triode structure alongside a bigger small signal pentode.

 

[pyrotas]

Yay, thanks!!!

Thank you all for the replies! If the bend is the one displayed in IMG_3111 yes, it is there. Does it mean the tube is near the end of its life 🙂 ? Concerning the audio-test, I am currently playing with a "Valvecaster" project which runs tubes in starved plate mode with 12V anodic voltage. I have indeed already tried it in my circuit (just crossing fingers and hoping not to blow out the whole house)...it works, flashes at the beginning and amplifies the signal. It has the lowest gain I have ever had in this circuit - sounds essentially clean even at "maximum gain". Sound is smooth and velvety and...well...I just love it! The only problem is I don't know the heater voltage: currently I apply 12V between pins 4 and 5, gotta see if this is OK or there's risk to burn it down. Possibly the circuit would need to be adapted a bit if this is not a twin triode but...just sounds great for clean tones!

I attach the schematics for the "Valvecaster" if anyone is interested.

Thanks again!
Ciao

Fabio

 

[pyrotas]

Forgot to mention that! The tube warms up much more than any other double triode I have ever tried in my circuit...

 

[mastodon]

Yes, most likely ECFxxx, but another possibility is an ECHxxx. Check if the cathode of the triode and the pentode/heptode are connected. If so, it's more likely to be a triode/heptode combination (ECHxxx). But due to a lack of shielding, I think ECFxxx is more likely.

 

[Tubelab_com]

It looks like a member of the 6U8 triode / pentode familly to me too. It probably has a 6.3 volt heater and it won't live too long on 12 volts.

 

[kevinkr]

Looks identical to Telefunken ECF82 (==6U8) triode pentodes that I have here. Mine have a getter flash on the glass over the aperture in the pentode plate which makes it hard to see there, but the rest is identical.
The triode plate looks like it is bent and separating as well, but it might just be distortion in the pic.

Gary

Looks to me like Gary is right. I have had a few of these in the past and they looked like this one IIRC..

 

[Tubelab_com]

At least here in the US there are dozens of triode / pentode tubes like these that all look the same but have slightly different characteristics. If I remember right there were two (maybe more) different non compatible pinouts. I am sure many of these have European equivalents. The 6U8, 6GH8, 6EA8, and the 6BL8 are all similar and can be substituted for each other in some circuits. There are other numbers that I don't remember now, that are similar. Your tube could be any of these.

 

[pyrotas]

Looks darn similar to a ECF82 according to what I see on google images. Thanks for the infos! I need to re-draw the circuit to really use this tube but seems worth the effort!

 

[rotaspec]

I have used various of the ECF series including ECF80, 82, 801, 802. They are all quite usable for audio.
The big problem I have struck with used examples is breakdown in the cathode/heater insulation, which leads to hum problems with ac heaters (and probably peculiar biasing problems with DC heaters). I have even seen this in supposed NOS examples.

Gary

 

[pyrotas]

The "miracle" is how the tube actually could work within that schematics! Poor heaters, they run for 5 minutes at 12V...

 

[cogsncogs]

Looking at IMG_3116, it looks like an EIA 9AE base. Pin 1 is the triode section's plate/anode and pin 9 is the triode section's grid. I'd lay odds it's an ECF82 (6U8), 6GH8, 6EA8, 6KD8, 6AX8 and so on. 6BL8, 6AN8, 6BR8 etc have a different pin-out. I've had zillions of them and yes they're good for audio.

 

[revintage]

Pyrotas,
If you´re into guitar-amps there is actually a great amp that uses the ECF82, Vox AC-10 Twin.

 

[pyrotas]

@revintage: the AC10 is a wonderful little beast! At the moment I'm experimenting with small booster/stompbox/whatever projects in the "starved plate" configuration. Started with the "traditional" valvecaster but I'm playing around with a friend of mine designing a crunch/boost around the ECF82 🙂