Light Bulb As a Vacuum Tube, Is This possible? #2

In an earlier video I showed that a light bulb with two filaments can be used as a diode. In this video I will try if it is also a usable triode with which you can build a tube amplifier.
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[@jrkorman]

Tubes containing a gas - see thyratron. Had to look up the specifics as it has been 40+ years since I was taught about those things!

[@Backwoods-Bob]

Had a sealed beam headlight bulb that had a rockchip in it. Filled up with rainwater above the filaments and it still worked.

[@zinckensteel]

Holy crap! I did a bunch of experiments on this very same topic a few years ago. I exclusively experimented with foil externally applied to the bulb as an electrostatic grid/control electrode. With a few carefully selected bulbs I was able to see linear audio band voltage gain of more than 1 but less than 2 during triode-like operation supporting little more than 150 microamps at best even with several hundred volts on the anode. Thyratron-like operation was much easier to achieve and could generally support a current of 1mA or more. I was not able to get one of these things to do anything useful at RF. I should add that I only used bulbs that showed signs of having a high vacuum rather than an inert gas fill. Hitting them with the discharge of a small tesla coil in a dark room will show a radically different kind of glow depending on the vacuum level. The classic purple filamentous arcs mean a bulb is unsuitable. Also, the bulbs will not last long when operating at more than 10mA - if you had observed the thing via welding glass you likely would have seen arc running from the cathode to the anode - I have run gassy bulbs in this manner, and the arc can be switched off with an external magnet, so it could be used as a latching thyratron of sorts, maybe.

[@agranero6]

Car lamps used on the headlights have an halogen gas inside. The gas reacts with the tungsten vapor and redeposits it to the filament avoiding it from get opened and to dark tungsten deposits to form on the glass. This reaction only happens at high temperatures, that is why halogen lamps work so hot. Normal lamps use argon because it is easier to fill it with an inert gas than to make vacuum, an d vacuum makes lamps to implode. Electron tubes can also be filled with gas (on the diagrams if the tube has a black dot inside it means a gaseous tube, like a tyratron).

[@tushar8133a]

Very well tried! Thanks for upload

[@pickoftheglitter]

very clever!

[@edgeeffect]

It would be really annoying if after spending all that time deliberately blowing the grid... if the cathode decided to blow on it's own.

[@Steven-re7xt]

Try a sheet of coper cladding isolated from ground but first burn one side to create oxide. Then you get more dc. From the light its selfe. Salute!

[@Kapcaniew]

I know it's not a new video, but I just came across a burnt H4 bulb from a car headlight and it reminded me of your attempt. H4 has a metal reflector that separates the two filaments - maybe this geometry would work better?

[@DoctorVolt]

H4 bulbs are filled with halogen gas. So I guess that they won´t work at all.

[@Kapcaniew]

@@DoctorVolt Ah, you are obviously right. It didn't occur to me that halogens are pressurized up to 8ATM, I was convinced it's still low pressure gas. Well then, my search for a weird light bulb continues.

[@michaelszczys8316]

There's probably one out there somewhere that will work. I know after watching this I'll be checking every old light bulb.

[@abasabasi8333]

Perfect

[@lebirb9497]

cute

[@DavidMills_Physicist]

Can you wind a coil around the bulb and use a magnetic effect to control the electron flow between cathode and anode?

[@DoctorVolt]

Yes, this could work. But I think that the effect would be too small, so that the bulb will still not amplify.

[@DavidMills_Physicist]

@@DoctorVolt I wonder if you could "bias" it off with a small permanent magnet, and then use the coil to reverse that field and allow a small current to flow. Might be a tricky engineering task to get it to work.

[@terrystearns1196]

Love your Experiments.. keep it up

[@ambikaprasadkapoor1178]

How about using them for Preamps. Especially Phono Preamp?????

[@DoctorVolt]

Because they do not amplify at all.

[@iwex7331]

Can it work like a rectifier diode with direct heating🤔

[@DoctorVolt]

Yes, but with very low current of a few milliamps.

[@SheikhN-bible-syndrome]

Can you make your own tube by filling a glass test tube with argon ? Or does it have to be a vacuum?

[@DoctorVolt]

It has to be a vacuum.

[@savadimitrijevic4668]

Can you make a simple two bit adder with it

[@DoctorVolt]

I could even build a computer with light bulbs. But I couldn't afford the electricity bill :)

[@noel3422]

Cheap ass bulbs last a long time wonder why tubes are so expensive lol.

[@weareallbeingwatched4602]

Wow. What the...