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Old 26th January 2011, 12:05 AM   #1
pyrotas is offline pyrotas  Italy
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Default Help identifying a Telefunken(?) tube...

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
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File Type: zip Tube.zip (725.2 KB, 77 views)
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Old 26th January 2011, 01:16 AM   #2
singa is offline singa  Singapore
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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.
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Old 26th January 2011, 01:16 AM   #3
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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.
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Old 26th January 2011, 01:35 AM   #4
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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

Last edited by rotaspec; 26th January 2011 at 01:43 AM.
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Old 26th January 2011, 01:44 AM   #5
gullaz is offline gullaz  Italy
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Looks very similar to an ecf82... must have an ecf82 tfk somewhere, I see if I can find it to compare with your pictures.
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Old 26th January 2011, 07:43 AM   #6
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it is an ECFxx for sure. A smaller triode structure alongside a bigger small signal pentode.
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Old 26th January 2011, 07:45 AM   #7
pyrotas is offline pyrotas  Italy
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Default 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
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File Type: gif MatsuminValveCaster.gif (18.3 KB, 133 views)
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Old 26th January 2011, 07:46 AM   #8
pyrotas is offline pyrotas  Italy
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Forgot to mention that! The tube warms up much more than any other double triode I have ever tried in my circuit...
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Old 26th January 2011, 08:00 AM   #9
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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.
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Old 26th January 2011, 04:38 PM   #10
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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.
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