Why Are Tubes Mirrored?
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- Опубліковано 8 лют 2025
- In this little video I give the Getter its due. Enjoy!
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Fran, I love your videos. I worked at Dosimeter Corporation of America for 10 years, and one of the processes in the manufacturing of a direct-reading dosimeter is high vacuum platinum sputtering onto a 7 micron diameter E-glass fiber to make it conductive for use as the moving line (magnified 80X) against a calibrated film reticle. The process requires a 3-stage ultra-high vacuum that is back filled multiple times with Argon gas before the 3rd and final vacuum stage using an oil filled Jet pump. Platinum ultimately gets deposited on the inside of the glass vacuum Bell Jar that results in the same mirror-like appearance as a Getter. I took advantage of our equipment to platinum sputter all sorts of personal items from paper clips to guitar parts. We also manufactured Geiger-Muller tubes, probed, and meters, possibly including the one that you are using in this video.
Sounds like it was a fun job. The way you worded it makes me think you no longer work there.
@@bentboybbz The company was purchased by Morgan Crucible of England, who purchased the company name, equipment, and technology and moved it overseas.
@@jts3339 Some jobs come with a nice sideline in bonus "stuff". Platinum deposition facilities sounds great.
I'm a Fitter/Engineer, I used to work down a coal mine. I could grab bolts and the odd thing from the stores. Kind of makes yours look a bit more special.
Can you re-silver a telescope mirror?
@@DemoCATicMAN I think its possible to do chemically maybe but has to be spun and done in a clean room ? Not my area maybe someone else knows more. Sorry im not of more help. Now i want to go down a rabbit hole about telescope mirrors lol.
That's cool, Fran. My dad, gone for many years now. Was an old-school TV repairman, Wess's TV repair. Cira 1958 - 1982. Banning, California. I asked dad what that shiny spot was for. He just told me, "That's just the way they're made." After all this time. Now I know. Thank you.
Interestingly, we use enzymatic biological equivalents of the getter concept to scavenge residual oxygen when studying strict anaerobic bacteria.
Beautiful tubes Fran!
What is your occupation, if I may ask?
Blessings r virtues
@@ianbutler1983 I'll bet he's some sort of microbiologist c:
Something I’ve always been too embarrassed to talk about. Glad you could explain it so well. Thanks 🙏
WOW! A 4-440A as an audio tube is real talk power! This was as much fun as the episode with the mechanical frequency meter.!
We used to use them in the RF bonding presses. Along with 6 GXU4 as a 3 phase rectifier.
Yeah that was fascinating. Hard to imagine how someone could come up with that mechanical concept. Genius!
I walked away from the screen as the "credits" were playing, but had to come back and rewatch the end to listen to the singing.
You're so right it will work out fine down the line.
However, let us pause to remember those who didn't make it through THAT year!
Getters similar in concept are used in some integrated circuits and other hermetically sealed electronics to absorb residual moisture and other contaminants. Now I know they go back to the vacuum tube era! Thanks, Fran, for another totally tubular video. You've been cranking out a lot of of them lately!
I love them
Exactly. There is getters in all OLED-displays.
Thanks!
You are most welcome.
I grew up in the 50's and fixed the old B& W TV's in my neighborhood in the Bronx. I took the tubes to the local pharmacy that had a tube tester and they had most of the tubes in stock. I infected my oldest son with my tube love and he is now a communications and computer engineer and has all tube stereo equipment. I also used to help rebuild CRT's and tuners. We would cut the guns out, process the CRT and re-flash it, replace the gun or guns and evacuate them before welding. I miss those days now you throw a TV away. I love your videos, thanks!
Fran. I enjoy your videos. In this video, you talk about the getter and say that it's got nitrogen and that it's dangerous. I saw that same mistake made almost 50 years ago in the Detroit Free Press regarding that gas being used in the early automotive air bags. They were talking about how dangerous the nitrogen was and inferred that it was explosive. It isn't. It is an inert gas similar to argon which was in the developmental air bags I worked on back in 1973. So just to make everyone not be afraid of nitrogen, it is not explosive or in any other way dangerous unless that is the only gas in the room you in, in which case you will suffocate.
Lady! You are giving me flashbacks!!!! My late hubby and I used to restore old radios, from RCA, Philco, to Zenith. Basement was filled with them. And some military radios too. I can't count how many of these guys I had to test one by one on the tube tester.
Voltage regulator tubes just look cool...the ones I had glowed purple...argon gas, I guess. They also make good relaxation oscillators.
Years ago, I saw transmitter tubes in operation at a small town radio station..they were glowing cherry red - I thought something was going wrong. The guy giving me the look around laughed, and said that was normal. He called them " coffee warmers"..
Some cars from the '80s had vacuum fluorescent displays.
Cool video!
Thank you for giving out the answer at the beginning! I'd have thought that either the mirroring was to increase efficiency by not requiring so much current to keep the emitter red hot, or that the mirroring was metal condensing on the glass while in use.
These are lovely objects! The expertise that was needed to devise them blows me away. You are so great Fran - I love your enthusiasm and smarts.
Tubes were such beautiful devices! I always found them fascinating, especially the inside! They were like tiny Terrariums to me, full of mystery and wonder!
Keeps 74 years Oldies like me nostalgic, eventhough I work with 5th generation electronics still.💖
I started out with Tubes and it's great to see some of them again, one tube that I liked the most was the 5R4 power regulator.
Yes, the 5R4 and it's sibling, the 5U4 are great looking rectifiers.
Wow! This brings back fond memories of assembling Dynaco tube amps and later, of splendid if pricey, McIntosh tube amps. Even order harmonics make for nice musicality. I bet your amp designs are works of art. It's a sobering thought that vacuum tube circuits can survive EMP events that will fry solid-state electronics back to the stone age. I'm honored, truly honored to be a subscriber now. Past engineering achievements are what inform future engineering achievements. Keep up the good work Fran. WTG!!!
I love your explanations of older technology. It's amazing how engineers solved problems. Sometimes with brute force!
That's the way edison did it. He tried failed and tried again. BTW. TAE DISCOVERED THIS BLACK EFFECT WHEN HE P UT A THIRD WIRE IN HIS ELECTRIC LAMPS
@@rsprockets7846 yeah Edison technically discovered the physical phenomena behind vacuum tube diodes in 1880 (an anode and cathode in a vacuum can act as an electric 'one way gate' only letting current flow one direction) but it took another 20 years for John Ambrose Fleming to realize that property could be used for radio detectors and invent the actual Diode tube.
@@drewgehringer7813
And including you too with your fairy tell stories. Be careful who you tell those fairy tales around in public.
Fran, you're a go getter!
Sir, step away from the keyboard and keep your hands where we can see them...Sir take your finger out of your nose.
@@kellyjackson7889 Hi Karen, do you GET it? GETTER? I love Fran.
@@njmikec Only if you put it on a plate after you've vacuumed.
Silvery tongued devil.
oooooh..........I get it!
I''m glad your bringing up some of these topics. Tubes are still used by hams especially in higher powered Amplifiers . That said, many of us with a little more experience with tubes are getting older and passing . I had heard that one of the little regulator tubes was radioactive. One site mentioned that a certain tube had it added or something wouldn't work quite right, but it wasn't a regulator.
What a pleasant presentation.
The high effort of working without a getter is reflected in the price of modern image intensifier tubes.
I like that a bit of the history of our technology is preserved like this on youtube.
Wonderful and accurate explaination of tube getters, and the reasons behind keeping the interior of tubes pure during the evacuation process. I've never heard or read it explained that carefully.
I never give you a thumb up nor comment, But you are incredibly smart and VERY clear explaining things not easy to explain. Thans a lot!
The RCA valve is gorgeous.
My eyes widened and mouth went agape when Fran displayed it
Right? I love that it was designed to be beautiful as well as functional. And surely very few people would see one of these in a transmitter.
Mildly scary, imagine the bang it would make if someone dropped it.
@@ThatBum42 OMG. Don't even joke about that. Forget the bang, what about the mess? :)
I was fortunate to witness these tubes in operation at an AM transmitter. The plates glowed with intensity that varied with the average audio level. I recall seeing bright orange at peak levels.
They couldn't flash that getter in the flat 2digit 7segmentdisplay because the conducting layer on the inside of the glass and the conducting kathodes on the back. And the thing is too flat to heat the getterring from besides. But what a great super rare display that is! Never saw them before, so that is why watching these video's is always something new to see and learn
I love the mystique of vacuum tubes and really appreciated this video. I'd love to hear/see more about your amplifier you said you designed. That's just too cool. Thanks Fran!
I am a retired high vacuum system glassblower. I checked thorium. It is an alpha emitter. Alpha particles do not penetrate paper, so the glass envelope of the vacuum tube will contain the alpha emissions of thorium
Filaments have been coated with thorium oxide for about 100 years to increase thermionic emission of electrons while running at a lower filament temperature. These filaments are used in mass spectrometers and other scientific equipment.
Doc Martin
Thank you.
I have worked with large ion gettering pumps and plenty of vacuum tubes.
Thanks for coverage of gettering.
I could listen to you all day, every day Fran. THANK YOU !
I studied (started in 1967) electrical engineering technology at Purdue University in West Lafayette, Indiana. One of my first courses covered vacuum tubes. Four years later I was hired as a full-time graduate instructor. My first teaching assignment that very same course on vacuum tubes. Much later (2000) I developed a curriculum on sustainable energy systems. One element included solar vacuum tubes to produce hot water. One of my students wanted to know the purpose of that shiny coating. I replied "getter" and then explained. Interesting that "new technology" still draws on basic concepts. My first electronics project was a one-tube radio receiver (using the 1S5). I was so excited (7th grade) when the filament glowed red. Having been a professor (and aerospace EE) for 40 years it was always fun to explain filament transformers.
I really enjoy that you use all your brain in things!
Thanks and love!
Dear Fran, I understand very little the English language, however I see many videos in English thanks to the subtitles that can be translated, I am an admirer of channels like yours and I would appreciate the opportunity of subtitles to better understand the contents.
Greetings and regards.
I had no idea of the concept of chemical vacuum pump. That's fascinating!
Also, I would tots buy the "I ❤ my Geiger counter" T-shirt.
They are used in the cern super collider to get the vacuum to the near absolute levels they need.
All of those years messing with tubes and I never knew this. My father had said something about it but I didn't pay a lot of attention at the time. Thanks Fran!
The silvering is from the Getter which was fired at the end of the pumping phase of manufacture after the valve was sealed. It absorbed any residual gas molecules that would interfere with valve operation. In the mid sixties I spent a summer vacation working in VM1 at Mullards Hackbridge. This was at the end of valve development for valve based television.
Ha - I just watched the Heathkit signal tracer vids and asked myself, why are tubes mirrored!!! Spot on Fran 😃
That RCA transmitter tube is so gorgeous!
High power RF tubes usually have two types of getter in them. The metal barium that is deposited at the base of the tube and the getters like zirconium on the Anode. The Anode getter is activated by use of the tube. When a old stock RF transmitter tube is first put into service the Anode getter should be activated over a period of about 100 hours with slowly increasing voltage applied to it. The final activation is done at full rated output power for a couple of hours.
Great explanation. I bet a lot of tubes got pulled when the mirroring got to a certain level when they were in fact perfectly operational. That last one looked like something from a 70s sci-fi movie. Wow!!
You were spot on, large tubes like the 833A and the Eimac transmitting tubes have zirconium covered anodes.
Zirconium is usually inhert but will react with oxigen when heated at higher temperatures, the colour of the plate during operation is usually specified in the tube datasheet (usually with words like "cherry red" or "mild orange").
They also can contain radioactive stuff, it mostly happens in larger tubes that required large glass-metal seals, it was common to use uranium glass on the joints to try and match the different thermal expansion of different materials :)
The Getter was always my favorite part of vacuum tubes. Its the unsung hero. Great video, those huge tubes are beautiful.
'My God I think she's got it!' .. A winning UA-cam format. Obscure but interesting items. Like a good wine she is improving over time.
Your knowledge Fran is always welcome and always fascinating.
I love you, Fran. You're a hybrid of Technology Connections and Periodic Videos.
I used to test TWTs...back in the 1980s at Varian Associates in Georgetown Ontario. They fired off the getter with an induction process. We used many types of technology to manufacture these glass tubes. I maintained a water cooled ruby laser spot welder for instance.
Wow Fran, I had watched a few videos featuring the large AM transmitter tubes, I believe it was David from El Paso Tube Amps, and knew they were larger than average output tubes, but had never seen them in someone’s hands before… They are really neat.. and large.. Thanks for posting…
I have a vacuum tube tester that does true tests of the tubes to show remaining life. Cant recall the name at the moment I picked it up at a salvage yard for 49$ and just replaced the capacitors with modern mylar film capacitors, works great
Broadcast Engineer here. 4 of the 833s were used in a 1 KW am transmitters. 2 were the
finals and 2 were used as modulators. 1000 Watts modulated by a 500 Watt audio amplifier.
Older Gates and RCA transmitters used 833s. 4-400s were used in Collins AM 1KW
transmitters. Also using 4. Again 2 were the finals and 2 were modulators.
Those are some pretty cool tubes! Especially the high power ones! I didn't know they operate at such high temps. One thing I like to collect is low pressure sodium lamps, and they also use a similar getter inside.
The getter material used on the plates of large transmitting tubes was typically zirconium hydride. Eimac used the trademarked name "Pyrovac". It only works at red-hot temperatures, so those tubes will tend to develop gas if used at significantly below their ratings.
Thanks for the info. When I find myself running one of these large tubes I will make sure I run it at the proper temperature.
I hope I'm as cool as Fran one day. What a great tube collection!
Thanks only took me 50 yrs to find this out I always wondered why they looked mirrored inside but was to lazy to look it up 👍👍👍
Love the channel I have a 12AX7A with what looks like a square getter.
It came out of a Hammond Organ preamp.
Tubes are beautiful. I remember when I powered an 1G3GT filament with a 12V transformer when I was a child. When I showed it to my father he said: "the first numbers of most valves are the HEATER VOLTAGE. This tube has an 1.5V filament so it can be powered by a few turns of wire on a vertical frequency oscillator of a TV." Even when he reprimand me he taught me something. PS: the filament didn't burned out: tubes were not made for planed obsolescence like lamps.
The HP or Tektronix frequency counters he used at work had Nixie tubes, I loved when he tooked me to work.
Thanks for making me remember him.
Some high power tubes (some 304TL specimens come to mind) also utilize uranium glass for the glass to metal seal around the pins, so that's another source of radioactivity
Yes, I spotted my Eimac 100-TH pair had a couple of green glows around the pins whilst I was messing around with a UV laser!
Seen racks of them. The engineers and glass lathe op's just called them "Canary" glass envelopes. Yes 304TL's WW2 version. They later stopped using the radioactive glass.
Every time you post a new video, I brighten up-- and I learn something.
Thanks for that clarifying bit of information I had always been concerned that the tubes I found with that mirroring on them we're nearing the end of their life now I know better thank you.
Awesome Video Fran!! That 300W Transmitter Tube is radical!!!
Thanks Fran. U R the bomb girl! I do think that YOU are the radioactive source in your world! Appreciate your efforts and talent! Greg @ Greg Guitars LLC
I often hear nonsense on UA-cam, but you have done quite well describing the process. On CRT's a mechanical 'roughing' pump was used, followed by a diffusion pump, followed by a cryogenic pump using ceramic beads and liquid nitrogen. All in all, it was about a 4 hour process. All the while the tubes were sitting in an electric oven to excite the molecular energy of gasses in the tube to hurry along the 'pump-down' process. Heating the getter by induction was indeed called 'flashing' the getter. After flashing, the vacuum would actually improve over time as the gasses 'stuck' to the getter flash. Over very long periods of time the biggest problem was/is helium seeping into the tube, because it will not combine with the barium and stick to the side of the glass. If you see a flash that has turned white it has "gone to air', and the tube is dead. Some knowledgeable people will 're-flash' a tube that has not been fully flashed and get a few more years of service out of it. That requires about a thousand Watt induction heater in close proximity.
While I never made Nixie tubes I do know that they are filled with a gas (neon?) that ionizes and glows, so they clearly don't need to have a high vacuum in the tube, which is what flashing barium getters is all about. I built CRT's for 'scopes and monitors at HP, and did all of the processes involved and that you described.
You brought me back to my youthness! Cheers!
That such items have been mass-produced for 100+ years staggers me!
I sell a lot of these and it still fascinates me that a 95-year-old tube can work perfectly well, and as new, after nearly a century. I love testing the real oldies.
In Russia tubes are still in mass production, mainly used in audio-amps by audiophiles who prefer the warmer analog sound.
There is the Great British Valve Project. They are getting various bits of valve making equipment together so they can start making valves again. Audio types as that's where the market is now.
Fran, Nixie tubes definitely have getters, however, it appears that they don't deposit material onto the glass envelope when flashed.
I have a clock made by Dalibor Farny in the Czech Republic. The R|Z568M tubes have a very visible getter at the top of the tube.
I have one tube that developed a leak in the envelope, causing the digits to develop dark spots.
I would be happy to send it to you for your collection. Even non-functional, it is a work of art, made by a true craftsman.
Dalibor has a UA-cam channel that is worth checking out as well.
Only a top flight engineer can say I'm no expert while she's explaining things that 99% of us never knew :)
flight engineer? waaaawwww
@@oswaldoriginal5037 I meant 'Top Flight' Engineer but there was a time those tubes were used in flight so.... maybe.
I used to build Dewars for high pass frequency filters and i used to have to precision weld into these stainless Dewars special getters that would help de-gass the Dewars when they were sucked down to virtual zero vacuums in a special "bake out" device, A dewar is a vacuum vessel.
Hi Fran. I have 2 of those Heathkit clocks. One is in my radio shack and has been in service [on] for +30 years. Yes they do look neat.
Wow, I simply never knew. Thanks Fran, I've learned something positive today.
Thank You for the BEST explanation and discussion of the getter I have heard in nearly 50 years in the electronics profession.
(I finally stopped working on boards when I would have needed to use a microscope to see & manipulate components.)
Anyone else here literally rolls into Frans teaching like your at school as a child and just found the best teacher ever. I do Thanks Fran ! ❤️❤️❤️
You were inadvertently advised to me. I'm sending you a gratitude card. I'm selecting my words carefully, because... You are a genius, scientist, tonality paramount...live opposite side of Pennsylvania and you have no ring.
Wow ! I'm glad I found Fran Lab . 🙂
I love Fran! Who'd think I'd be learning about vacuum tubes while I do my lunch time workout? So glad I discovered this brilliant person.
I had not heard the word 'getter' in so many years. Admittedly, I did not know what that was (I had worked with the color picture tubes).
Interesting video!!
Very interesting ! Your handiwork with the Vacuum devices, and your name-remind me of Gruff Ole' Billy Gibbons singing "Francine". Nicely explained !
I knew a little about getters, but this helped fill in the rest. Also , love the singing and F-bombs at the end end.
WRMI, 1.4 MW shortwave station in okeechobee fla. what is really wild is how some of the old MW stations used water cooled final power tubes. The rf voltage was so high that you couldn’t be in the transmitter enclosure when energized. One old station I watched had it’s own rotary DC converters to run the transmitter.
G'day Fran... What you need to find is an old Thyratron tube. If you get one of the more active ones, it will DEFINITELY 'trigger' your Geiger counter.
(Just like Neon Tubes that don't want to 'fire' when they're completely in a dark enclosure, a Thyratron used random nuclear decay to help it to trigger)
Growing up in reseda CA in the 70s my brother and I would go 'dumpster diving' at the local 'Marvac' store for tubes. accumulated a huge collection. later on found a discarded excellent tube tester (dumpster mining again) as big as a small steamer chest (looked like one to when closed) had a test setting guide inside it to. Tested our collection and 90% were perfectly OK. Became too cool (in the 80s) to keep track of our treasures. I lament the loss.
I always thought it was a reflector of sorts, you learn something new every day
Christ, if one didn't know that, one should not be working on vacuum tube equipment. When I was went to electronics school in 1979, they were still teaching vacuum tubes! Thank God, as that training has been very valuable to me throughout my hobby and work life. I sill enjoy vacuum tube radio and amplifier equipment.
I imagine a lot of healthy, high quality, and even rare tubes were trashed because they were thought to be blown based on the look of the getter. This is truly one those "never woulda thunk it" videos.
Keep making us smarter Fran. We luv what ya do!
I thought I knew about vacuum tube getters. I learned a few things... Thanks Fran !!!
This is awesome, I always wondered about that!
I got into tubes with guitar amps and after I built my first guitar amp I've been all about the electron tubes
now I haven't sought out many vacuum tubes, but omg that RCA tube is enormous, the largest I can ever recall seeing!
Fran, thank the gods you made a video today. After the day’s madness I’ve been full of panic, but your videos have an excellent calming effect on me.
I’m not an electronics nerd but those tubes make me want a reason to have some in my life, when you busted out that first big-ass one I uttered a loud “WOOOOOOOOW”
Always thought that silver deposit was some sort of aging, high temperature cathode spitting off metal atoms or something. Wow, I've learned something new today. Great video.
Tubes~!! My wife says that they multiply at night!! I guess cuz I have collected like a lot of them! Building musical equipment tube amps you come to appreciate the valve/tube for what they represent - works of art! Though I knew about the getter and like seeing them in the various shapes and sizes you did a great job of explaining the reason behind the silver laden area on a vacuum tube! That 300B is a great example of a vacuum tube and worth a lot of money! A pair of New Old Stock..NOS go for around 10K! Johnne
Thank-you Fran, you are my Mentor of the day.
I love vacuum tubes! I rebuild old vacuum tube radios and televisions and transceivers, "Short wave radio transmitters and receivers.". :) I love the vacuum tubes!
Currently building a guitar tube 5u4 rect, 6j7 pres 6n7 mixer 6l6 field coil speaker!!! Almost biased, kept it a little lower and I'm going to the dreaded "hunt the ground loop hum" game☺️
Fran is very informative, and a pretty good singer as well.
Peace and love from Italy.
Tubes are mirrored so you can hold one in your hand and see your reflection. Then you can draw yourself and do your autobiographical work like M.C. Escher did with the silvered globe. I always thought that was one of the best pieces of art ever made.
Art and Engineering come together. Been fascinated with tubes since I was a boy making amplifiers. My parents had no clue I was playing with such high voltages :-)
Fascinating! I suppose I always figured it was either some type of shielding or otherwise deposited metal vapor from the manufacturing.
It's getter. To remove the last air molecules after vacuum pumping.
I bought five 4 pin valves for £6 at a radio rally and inspecting them at home one was marked D.E.R. with a BBC stamp on the glass and has a pip on top where the valve was sealed. The body part of the valve is metal.
This dates it between 1924 and 1927 and it amazingly still works! Its tungsten filament lights it up like a light bulb.
I like valves and a few years ago made a one valve transmitter for Morse Code, 2 Watts out using a BT61 out of a non working oscilloscope.
G4GHB.
I started my training on valves in the Air Force (RAF) because we were pretty backward ! Spent many hours behind the old AVO valve tester with a mountain of suspect valves ! I knew about gettering but not to the level you describe.
Very informative! I had always wondered about the "mirroring", or as I now know, the getters!
Cathode ray tubes (picture tubes) also have a getter inside them. The getter ring is located on the end of a long, curved metal strip that is connected to the electron gun assembly. When the electron gun assembly is mated to the neck of the CRT the getter goes in first and then it slides down the bottom inner surface of the glass bell. Then its fired off by putting the tube in an oven. There is usually an outer conductive covering on the tube bell so you can't see the black mark.
Fran you have achieved a level of geekiness that I can only dream of! I love it! Will be watching a lot of your video’s from here out.
Just an amazing video. I like how you explain things so that I, a layman, can understand them.
Million thumbs up.
👍👍🍻🍻🤘🤘🤘🤘🤘