What thyratrons are _really_ good at, is moving huge amounts of current in very short times. They are used as pulse formers for currents of hundreds or thousands of amperes. They are also very good at making very short pulses. If you have a capacitor charged at a very high voltage, a thyratron can get all of the charge out of it very quickly. They are still, to this day, better at doing that than semiconductor devices like BJTs, FETs, thyristors and triacs. And they do that in a very reliable and reproducible manner. A special version of thyratron called krytron, is used in the ignition circuit of nuclear bombs.

Excellent video! Thyratron tubes were actually used extensively in industrial applications as rectifiers, and in speed controls for DC motors. I have a Monarch 10ee metal lathe from the late 1950s that uses a Thyratron variable speed DC drive. It uses four thyratrons in total: two large C16J argon thyratrons and two smaller (but still big) 3C23 mercury vapor thyratrons. The mercury thyratrons glow a brilliant blue when operating, and the larger argon tubes glow, but much dimmer. The operation of the drive is very interesting. There are two sets of thyratrons to form two full-wave rectifiers. The larger C16J tubes control the voltage on the armature of the DC motor, and the smaller 3C23 tubes control the field. The speed control consists of two wire-wound rheostats which control the two rectifiers. Each set of thyratrons has a capacitor connected to the grid. When the thyratron fires (once each cycle of the input AC), the grid current causes the capacitor to charge a bit, eventually charging it enough to create a sufficient bias on the grid to prevent the tube from firing. This stops the operation of the drive. The speed control rheostat is connected to a control tube that discharges the capacitor at a controlled rate. When the capacitor discharges enough to allow the tube to fire again, the tube fires until the grid current charges the capacitor again. Based upon how fast the tube discharges the capacitor, the circuit will begin to oscillate, eventually getting to the point where the discharge rate of the capacitor exceeds the grid current, causing the tube to fire on every cycle. When the armature is at full voltage, the second half of the speed control does the opposite: it ramps down the voltage applied to the field of the DC motor, allowing it to spin faster. The whole system is basically a gigantic tube-controlled PWM speed control. It was particularly advanced for the time as it also included circuitry to detect load on the lathe and automatically adjust the voltage on the motor to keep it running at a constant speed. I have thought about eventually making a few videos outlining the operation of the machine, and showing how to diagnose it, as most people with the machine are stumped by the drive. Unfortunately, the common remedy is to rip it out and shove in a generic modern drive that does not come close to the performance of the original.

Thank you for the video! I did not realize thyratrons could be operated at such low voltages. I have never had these to play with.

I first heard about thyratrons this afternoon (some $375K turntable [yes, apparently people buy such things] uses one in its power supply). Now, thanks to your video I feel I know a lot about them. Thank you, again!

Perfect explanation! Thanks!

Thyratrons were used in spot welding controllers for the car manufacturing industry. Difficult to fault find because the circuits were high impedance.

From what I read Thyratrons were used in many applications, including relay controllers, early computers, tool motor controllers, switches, stage light dimming, fluorescent dimmer ballasts, stepper controls, jukeboxes, lasers, tesla coils, radar systems, industrial equipment, welders, elevators, and other applications back in the day.

The third schematic could be used as crude PWM if the control grid were connected to a potentiometer. It would make the halogen bulb dimmable. Similar to thyristor based dimmers.

Great video! I was experimenting a while back with using a vacuum tube to drive a high current load. I found that even a small 6AU6 can drive a 24 volt relay coil. You could potentially use this property to reset the latched thyratron tube.

A Thyratron can be used to easily make a voltage-controlled sawtooth oscillator.

this is LIT, you're awesome man

Thank you for this interesting video. I'd like to build an oscillator circuit with the 2D21=PL21, that generates tilting oscillations as are used for sound generation in the so called 'Trautonium'. Do you have an idea how to generate tilting oscillations with the thyratron?

Would the regular 6AU6 tube manage to power the bulb if it were powered with it's regular rated voltage of at least 100V or so? Also I did not know 47 bulbs were halogen. Is that all of them or is the 47 denomination just the base identifier? love your videos!

Brilliant. You should have used that 16vac transformer when demonstrating the Diode valves in part 1 of your series.

Thank you sir. Can thyratron be used in 12 kv circuits n so on?

What would happen if the heater was disconnected from the thyratron while turned on? Would the ionisation continue unaffected, or would the voltage drop change due to temperature effects on ionisation? Something to consider for science.

This is the nice looking version of a Thyristor ! Makes me want to latch ON/OFF all my circuits with it. I was expecting that we would see the ionized xenon. Anode is masking the glow ?

20:40 Can this be used in phase control? Maybe if you replaced the resistor with a potentiometer to form a voltage divider with the wiper going to the grid.

I am being pedantic a bit, but technically its not a "halogen" bulb. It's just a standard incandescent bulb. Halogen are a specific type depending on the gas inside the glass envelope. Yeah, I know I am just being pedantic with that :) I love valve / tube technology. I know it's not quite as efficient as solid state technology, but it just fascinates me the way it works

nice; i too am fascinated at these "parents" of the "transistor"! (Btw for fun did u catch the hollywood movie with the ENTIRE plot centered on the "krytron"? guys nite to watch?)

nice differential shirt🚗

Those little thyratrons have been obsolete since SCRs were invented. But I've used larger hydrogen thyratrons as switches in radar transmitters. A 7890 will switch hundreds of amps at 40 KV. I've also used ignitrons to fire somewhat more power but they can be jittery. Plus they contain maybe a pound of mercury each. Small thyratrons (from EG&G) were also used as triggers for nuclear bombs.

It's like a tube version of a Thyristor?

Sure you learn a lot about it. However you could use miniature incadescents like those used in Christmas lights. These are 3v and their current is low.

15:37: "We need a manual button, and I haven't come up with a good way to get around that issue." How about another thyratron? 😛 PS: It's thyratrons all the way down.

Are those bulbs actually halogen or are they just ordinary incandescents?

5:19: "The control grid gets kind of encased in positive ions."

Could you please explain the use of shield grid?

15:33 what about relays?

Here's an interesting little bit of trivia for you, the word Thyratron comes from the Greek word Thyros, which means Door, so, a Thyratron is literally a Door Tube, you could think of a Thyratron as being like a voltage-controlled switch.

Can you see the glow from the tube though?

7:19: "It's essentially like a switch."

You can use the 6V DC as his own Heater Voltage :O)_)

also deuterium

Put you button on the controlgrid, the you should be able to control the bulb.

Never saw a #47 bulb filled with Halogen gas. Who knew?

well, there's another way to make a single bit of memory using a tube, thyratron sram...

how about a latch with a thyrathron edit: oh well we thought the same thing i guess xD

it acts like a thyristor

one bit memory