Mystery tubes

[frokost]

I pulled a few tubes out of an old radio, and the markings on two of them are gone. So any idea what these tubes might be? I suppose the one that says "84" is an EL84? The other one has no markings.




The other tubes i pulled out are:

1xEZ80
2xEF89
1xECC85
1xECH81

All Telefunken.

Any idea?

[JasonG]

Where were they in the circuit ?

[frokost]

I don't know. The radio was going to the dump, and I just grabbed what I could in there. I don't know what radio it was either.

[Dragonfly]

The bottom one is indeed an EL84

compare to a "known" Telefunken EL84 and the lettering / etc match up.

[frokost]

Thanks, that's what I thought. What about the other one? It looks nothing like the rest.

EDIT: BTW, these things must be old. The markings disappear when I touch it (I'm thinking that the markings were removed when I pulled them out). Some of them also had a paper band around them, and when I bend it it turns to dust.

[BubbaKahuna]

The EZ80 is a full wave rectifier, very common in guitar amps, hi-fi gear & ham radios with tube recs
The EF89 is a variable μ pentode for use as an RF or IF amplifier in FM/AM receivers and is designed to work with a tuned anode circuit
The ECC85 also know as a 6AQ8 is a preamp tube (TubeDepot gets $80 for this tube used) - medium gain IIRC
The ECH81 (also known as 6AJ8) triode heptode was designed for the role of frequency changer (mixer) in superhet receivers, the two valves share a common cathode.

I'd say for amp builders your real score is the EZ80 & ECC85 tubes, and of course the Telefunken EL84s (killer tubes and Very Expen$ive).
Ham and radio hi-fi guys might want the others.

Too bad you didn't snag the power & output transformers.
If they were powering EL84s & 3 or 4 other tubes in there, you'd might have had an easy build for an 18W Marshall clone using the guts.

As far as assuming age by failing printing, there are other things that can destroy ink, like heat & humidity.
Being that they're all unknown quality (and might be why the radio was trashed in the first place), I'd suggest you get them all tested.
Make jewelry and Xmas ornaments from any junkers and either use or sell the good ones.
Sell the ones that test borderline good with a disclosure that they aren't strong.
Someone will buy them for spares or build-testing.

I love finding stuff like that on curbs! 

Cheers,
- JJ

[frokost]

Great info, much obliged.

Yes, too bad about the transformers, now that you mention it. Didn't think about that. I hadn't planned on building an amp... before now 

Still don't know what the last tube is. I tried to search for "telefunken tube" on ebay, but none of the tubes there looked like the one I have.

[the_ms]

Still don't know what the last tube is. I tried to search for "telefunken tube" on ebay, but none of the tubes there looked like the one I have.

It is probably an EABC80. It contains three diodes (for AM and FM demodulation) and an audio preamp triode. It could be recognised very well by containing three systems.
The Tube set ECC85, ECH81, EF89, EABC80, EL84 is very common for german radios in the late fifties.

The ECC85 was not designed as audio preamp tube but as FM (VHF) buffer stage and mixer, but it could be used as one as well.

[frokost]

That looks like the one I have. So I don't suppose it will be useful for amp/stompbox use? Or could the diodes be used for clipping and the triode as a, ahem, triode?

I really don't know that much about tubes. But thanks to all for helping me out here.

[the_ms]

That looks like the one I have. So I don't suppose it will be useful for amp/stompbox use? Or could the diodes be used for clipping and the triode as a, ahem, triode?

Yes, the triode section of the EABC80 (also known as 6AK8) is *similar* (with different parameters) to one half of a 12AX7 and could be used like that, even with low voltages.

I doubt if the diodes could be used for clipping because they have no knee voltage like semiconductors (e.g. 0.7 for a silicon diode). They start conducting at 0V or even in the negative voltage range (but with positive current), considering the phenomenon called "Anlaufstrom" in german (I don't know the english expression, sorry).

[ambulancevoice]

http://www.r-type.org/exhib/aaa0405.htm

[frokost]

ambulancevoice: That's the picture I saw when I concluded that my tube was the same.

the_ms: Good to know. So it is useful for something. Maybe I should throw together a mojobooster or something  .