ECC83S and EL84 : huh ?
Yann Guidon / YGDES wrote 03/10/2017 at 15:45 • 0 pointsApparently, one of my neighbours has "revalved" his amp.
I'm surrounded by musicians so apparently, one of them has changed all the chinese tubes with slovak ones. He conveniently left the original tubes in the common space. I end up with (equivalents of) 4×ECC83S (preamp ?) and 4×EL84 (amp ?) of unknown vintage. Some might be disfunctional, no trace of dust or heat, only one might have burned inside, a bit. One might have burned and the guy changed the whole set "because you never know".
WTF do I do with that ?
I'm not a tube/valve amateur and I loathe any component that heat and/or requires high voltages (doesn't bode well, huh ?) but the temptation is latent.
Analog circuits would be too messy and useless. I have plenty of fun ahead with my relays (as wel as the many germanium and silicon transistors) and it's out of question to start a computing project with tubes. However I think a demo project with a few of them, maybe an ECL-equivalent logic gate, would serve as an "educational resource" (as in: you see, keeds, grand-grand-dad used to rely on these glowing hot dangerous things, before the transistor came to the rescue)
Since I have no idea of the specs (I could google them I know), and 8 tubes (or realistically maybe 6) is very limited, can anybody help and hint at practical, interesting and/or useful applications ?
Something with an oscillator, a latch, a logic gate...
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Whelp, I see you're not into analog, but others may be...
Not specific to your tubes, but tubes in general:
Couple simple-ish circuits (one tube) I found in RCA's "Receiving Tube Manual":
Code-Practice Oscillator, Volt-Ohm Meter, DC Power Supplies (using tube[s] as rectifying diodes), Automatic Volume Control, Voltage Doubler...
There's more complicated stuff in there, including FM-demodulation (in stereo!), and everything needed to design a TV, in color, described stage-by-stage (each stage being only ~3 tubes!).
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I vaguely recall having an old science-projects-for-kids book that illustrated a really simple tube circuit, they recommended using modelling-clay (or gum?) squished against the side of the tube, down onto a block of wood, as the mounting-method (tube laying sideways). Spose aligator-clips would be the logical wiring-choice.
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Wow... I'll try to do something safer :-D
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Bah! Safety... I suppose you'll be wearing a lab-coat and goggles, as well?
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Hah, found it... I've thrown up an image/PDF over at: https://hackaday.io/project/5447-had-image-host/log/56334-simple-vacuum-tube-experiment
Memory was a bit sideways, but otherwise, it's a really simple experiment involving only a tube, 12V, and an ammeter.
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Bad eBay.
Bad bad BAAAAAAD eBay.
It got me a box of 1J29B-V (1Ж29Б-В) pentodes from Moldova.
The HF pentods can work as NAND/NOR gates, right ?
They are cuuute, tiny, use only 60V, require less power and run faster.
That could be enough to build a small adder :-)
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The ECC83-replacing tubes I got are marked "7025 CHINA".
No idea about the gain or speed.
All I know is that a double triode can do a single flip-flop, or a differential amp, or 2 NAND (with the necessary diodes). Maybe one XOR gate even. I'm not going far...
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ECC83s (also known as 12AX7s) are twin-triode preamp valves. EL84(6BQ7s)s are output pentodes.
Thing about valves is that they need loads of support - sockets, high voltage power supplies, high current heater supplies, output transformers etc. etc. Which means that you get very few bangs for your hobbyist buck. Also, you need to consider why anyone would throw these things out. EL84s are pretty fragile and (especially Chinese ones) don't last long in a well thrashed amp. The ECC83s will probably be OK.
Its perfectly possible to build gates and latches with them - if you have a convenient 100V DC supply and 6.3V to go on the heaters. But audio is probably more interesting. RC Oscillators are quite easy to build. Build two or three and mix the outputs for synthy experimentation?
Maybe use an a couple of ECC83s in push-pull headphone amp (you'd need an output transformer).
Maybe build a Theremin?
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Thank you Ted !
I'm not interested by audio applications :-)
the EL84 might be useful to drive an output (lamp ?) and one ECC83 could hold a latch (if it's dual).
I'm curious about speed : how fast can a ECC83 commute digital data ?
Yes, support parts is going to be an issue so I try to keep the part count low while trying to make something "somehow significant".
A LFSR ? Not enough ECC83s...
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dude, just build another tube amp...
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Brian, are you Sirius ?...
I don't care a damn about amplifiers. Why even bother in this day and age, when I can do much much much better with an OPA30x ?
Now, what if I could try to reproduce one gate or circuit module of ENIAC or Atanassoff's engine ? Speaking of which, a serial adder would be a great example : one FlipFlop and a 1-bit full adder. how'bout that, Brian ?
Remember : it's (a warning) for the keeeeeds :-)
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