I believe these vacuum tubes were used as resistors back in the old days. Is that correct? I want to buy this circuit to dismantle the vacuum tubes and use them in my project just for the visual display to show a burning glow that emits light. It would be great if these were integrated into a bigger design, such that the vacuum tube are serving their purpose.
encryptor:
I believe these vacuum tubes were used as resistors back in the old days. Is that correct? I want to buy this circuit to dismantle the vacuum tubes and use them in my project just for the visual display to show a burning glow that emits light. It would be great if these were integrated into a bigger design, such that the vacuum tube are serving their purpose.
LOL, you are quite the comedian. Vacuum tubes are roughly analogous to the FET of today. Some were electrically equivalent to diodes.
That circuit board is a hoax if they are advertising it as a 1950's prototype. While the tubes could very well be from the '50's, some of the integrated circuits and transistors have date codes from the '70's. Not to mention there were no integrated circuits like those in the '50's. There might be $15 worth of nostalgia in those old vacuum tubes but I wouldn't count on them being good for anything else.
that's exactly it - nostalgia. I want to bring back vacuum tubes to shows their 6-8 glowing points from the 70s. People would find this to be educational and fun! 8)
encryptor:
that's exactly it - nostalgia. I want to bring back vacuum tubes to shows their 6-8 glowing points from the 70s. People would find this to be educational and fun! 8)
I think that's a good goal. You could build a simple stereo preamp out of tubes and have a real conversation piece as well as a useful gadget. As for those tubes, you'd have to look up the part numbers, they may well be from the '50s but the rest of that circuit board is not.
A common filament voltage for vacuum tubes was 6.3 VAC. There are many transformers available at that voltage for that reason. Get one and light it up!
There is still a thriving niche market for vacuum tubes, mostly from NOS (new old stock) but there are still new vacuum tubes being made overseas, Russia and China for sure. These cater to the golden ears hi-fi crowd, old and new electric guitar amplifiers, and ham radio world where hams need replacements for restoration of older ham radio equipment. About a year ago I bought a Kenwood TS-520S ham radio tranceiver made in the mid 70s, It's a hybrid solid state/vacuum tube rig that uses 3 tubes in it's transmitter final section, one driver tube and two power tubes. It uses the very popular 6146B final tubes and the prices for NOS on e-bay can be quite high. I waited about four months until finding a pair for $20 which was about half of going price.
Still to this day the majority of brand new commercial ham radio 2 kilowatt linear amplifiers still utilize vacuum tube finals rather then transistor finals.
Lefty WA6TKD
WA6TKD
Wow, WA6 would rank to the age of classics. What are they up to now, WZ6?
oric_dan(333):
WA6TKD
Wow, WA6 would rank to the age of classics. What are they up to now, WZ6?
Actually for a while now the FCC have allowed hams to pick their call sign if it's not presently assigned to someone, so an old call sign could very well be a fairly new and young ham. There called 'vanity calls', much like one can get vanity license plates in most states these days. But indeed I 'earned' my call the old fashion way by just being old. Now are you free to mow my lawn? 
Lefty
Now are you free to mow my lawn?
The only thing free is help on this forum.
No doubt! Now that I know vacuum tube diodes are still being made, would it be difficult to wire up? How would I wire up the 8 pins?
Do all vacuum tube diodes glow? Which ones glow the brightest? If I knew the voltage or current it draws I can buy the proper resistor. Free help in the forum..nicee!!
Still to this day the majority of brand new commercial ham radio 2 kilowatt linear amplifiers still utilize vacuum tube finals rather then transistor finals
Why vacuum tube finals over transistor finals? What is meant by finals?
Why vacuum tube finals over transistor finals? What is meant by finals?
Finals mean the active devices (transistors or tubes) used in the final stage of an amplifier circuit where the high voltage and current are used to generate the desired output power for the amplifier. There are of course high power transistors available to build a 2KW output transmitter, but they required massive heatsinking compared to modest fan cooling of comparable power tubes and because the transistors can't normally work at the very high voltages of tubes the solid state amps require high current flow construction which offsets some cost savings. New high power linear amplifiers are to this day still somewhat cheaper if made with tube finals Vs transistor finals.
Lefty
A WAG: I think the tubes are EC20 pentodes.
No doubt! Now that I know vacuum tube diodes are still being made, would it be difficult to wire up? How would I wire up the 8 pins?
If you just want to light it up, there should be two pins for the heater filament... EASY! You'll have to look-up the pinout, and check the specs/datasheet for the filament voltage & current. The filament pins are probably standardized, but I don't even remamber how to "count" the pins on a tube.
Her's the spec sheet for a [u]6L6[/u]. The heater pins are 2 & 7, and it needs 6.2V (AC or DC) at 0.9 Amps.
Or if you have a multimeter, you can just find the two pins with resistance between them (most pins will measure "open" with no voltage applied to the tube).
Making something useful, like a preamp, with a tube is not quite so easy. It requires higher voltage (typically more than 100V) and more components than making a preamp with an op-amp. And, it's trickier to get good performance. Stuff is a LOT cheaper & easier with modern electronics!!!!
retrolefty:
Why vacuum tube finals over transistor finals? What is meant by finals?
Finals mean the active devices (transistors or tubes) used in the final stage of an amplifier circuit where the high voltage and current are used to generate the desired output power for the amplifier. There are of course high power transistors available to build a 2KW output transmitter, but they required massive heatsinking compared to modest fan cooling of comparable power tubes and because the transistors can't normally work at the very high voltages of tubes the solid state amps require high current flow construction which offsets some cost savings. New high power linear amplifiers are to this day still somewhat cheaper if made with tube finals Vs transistor finals.
Lefty
And RF transistors are limited to low voltages so the output stage has to be low impedance (few ohms), which causes issues matching IIRC. Also mismatched VSWR can burn out the transistors due to the lack of robustness. Years ago I started to build a 2m amp with a 3CX250B valve,
which runs at 1.5kV upto 0.25A, an impedance of a few kohms, now that does glow at full current (blue-white fluorescence of the ceramic valve body I believe!)
It's readily possible to operate a 6C4 or any of the 12A?7 (12AT7, 12AX7) with 12 to 20 volts on the plate and get 20 Db of gain (a voltage gain of 10X) easily. I built a 'starved current' amplifier that used a 12 V B+ source and it worked very well. When I started in electronics there were FEW silicon diodes available and all were small signal devices. Selenium rectifiers were King (Horribly Nasty smell when on shorted, which was a frequent occurrence) 12V battery chargers has tubes called Tungar Rectifiers,. Smaller 12 V power supplies for high current used copper oxide rectifiers (Circa 1959, I was 13). 'Portable Radios' had tubes in them, many of which worked with a volt to a volt and a half on the filament and 22.5V on the plate. I still own a 2RP4 which is a 2" electrostatic deflection cathode ray tube (CRT) I am just too lazy to make a 1200v (@ ~5mA) supply and the deflection drivers are serious too. There were No real solid state devices like there are today. I remember building my first am radio with a piece of lead sulphide (Galena) for the "Cat Whisker" detector. It worked well, I was able to add a speaker and a matching transformer for the local clear channel station, free power was alive even then as the crystal set only required a long wire antenna and a set of headphones (Not today's earbuds). Stereo was not yet really conceived and not every house had television, Color television I mean. Radio was still a source of entertainment. I remember the radio programs of the 50's, The Lone Ranger was one of my favorites. Today is so very different and it is a great time to be alive. The discoveries I've seem are truly awesome and the future looks even more interesting... From an Old Geezer, who remembers...
Doc
Today is so very different and it is a great time to be alive. The discoveries I've seem are truly awesome and the future looks even more interesting... From an Old Geezer, who remembers...
I suspect our generation will be somewhat unique in the total scope of change in technology from the second half of the 20th century to present, that is post WWII to present. The tech will still continue to progress forward of course, but the scope of total change will probably never match what we have seen over our lifetimes as early 'baby boomers'. That is of course assuming the space aliens don't show up soon.
And yes, shorted out Selenium rectifiers was the worst smell ever.
Lefty
@Lefty, I am thinking that advances in quantum electronics is going to be bigger than all integrated electronics put together... Primarily because it will be built on that framework as the basis for the likely near future (Our lifetimes). Little things are totally amazing, My room-mate (My Ex Wife) bought a Keurig Coffee Maker that has a rather sophisticated controller internally.... Comes a long way from Mr Coffee... Ugggh Crappy Coffee Makers.
Bob
Docedison:
@Lefty, I am thinking that advances in quantum electronics is going to be bigger than all integrated electronics put together... Primarily because it will be built on that framework as the basis for the likely near future (Our lifetimes). Little things are totally amazing, My room-mate (My Ex Wife) bought a Keurig Coffee Maker that has a rather sophisticated controller internally.... Comes a long way from Mr Coffee... Ugggh Crappy Coffee Makers.Bob
Maybe, but then again practical nuclear fusion reactors have always been just 'ten years away' for most of my adult lifetime, so our ability to predict future changes and progress in tech is no where as good as are ability to see how far we have come. Not all tech works out, intel put millions into 'bubble memory' if you recall, which flopped in the market place, and my practical and affordable flying car has still not showed up.
Lefty
Los Angeles Freeways have Proven the impracticability of a flying car.... Too Damn Many People looking for the fastest way... You see them cutting in and out of traffic and usually get to the same odd ramp within seconds of each other... Perhaps not your Flying Car... but certainly Dick Tracey's Wrist Radio/TV has been in production for some time...
Bob
Los Angeles Freeways have Proven the impracticability of a flying car.... Too Damn Many People looking for the fastest way... You see them cutting in and out of traffic and usually get to the same odd ramp within seconds of each other...
You obviously don't see the motorcycles, cause they're getting off at Santa Monica while you're
stopped dead at Ventura.