Here is a nice night shot of a Phillips #47 Directly Heated Pentode. These had some of the nicest blue glow of any valves I've had.
An externally hosted image should be here but it was not working when we last tested it.
If the glow disappears after a while its prolly resudial gas getting absorbed by the getter as the tube heats up.
The glow from punishing a tube i think comes from outgassing or possibly an electron cloud so dense that it becomes visible, electrons are said to be blue.
The glow from punishing a tube i think comes from outgassing or possibly an electron cloud so dense that it becomes visible, electrons are said to be blue.
The 6V6GT's were glow of the "second kind" gassy tubes (post #11), very gassy tubes. The 6P3 picture is not mine. It was taken with a Canon Power Shot A560 and I use a Sony.
I used some RCA 1625s in my "Shrine" amp that pretty much glowed all over (the right kind) there's a photo in the thread for that amp. I switched to some Sylvanias. They sounded a little better, but don't glow at all.
Winged =C= 6550C, 669v anode, 330v screen, fixed bias @ ~75% max dissipation
Was the first time I fired up that amp. Love at first glow 😉
An externally hosted image should be here but it was not working when we last tested it.
Was the first time I fired up that amp. Love at first glow 😉
The intensity of the glow (first type) depends on the current (number of electrons escaping --> number of collisions with impurities) and the plate-to-cathode voltage (energy of each electron --> probability of a collision resulting in excitation of the impurity).
Unfortunately, in amplifiers, as the tube current goes up, plate-to-cathode voltage goes down. So sound modulation of the glow is not as large as it could have been.
For maximum effect, use a push-pull amp with fairly low bias, and play some loud music.
Unfortunately, in amplifiers, as the tube current goes up, plate-to-cathode voltage goes down. So sound modulation of the glow is not as large as it could have been.
For maximum effect, use a push-pull amp with fairly low bias, and play some loud music.
Here is anice page on blue glow- lots of nice photos!
Blue Glow in Electron tubes
(The section "fluorescence type 2" is either caused by flourescence of calcium impurities in the filament/cathode material, and possibly by neutralization of trace gas in the triode. In pentodes a similar glow occurs around the suppressor grid, again due to neutralization of trace gas. This is normal)
Blue Glow in Electron tubes
(The section "fluorescence type 2" is either caused by flourescence of calcium impurities in the filament/cathode material, and possibly by neutralization of trace gas in the triode. In pentodes a similar glow occurs around the suppressor grid, again due to neutralization of trace gas. This is normal)
In my amps, any blue glow will flicker out when the amp goes into clipping (tubes going into cut off). Easy way to tell at a glance why it sounds bad. 🙂 The rest of the time it is pretty steady.
My first amp was an organ pull and the Sylvania 6V6GTs in there glowed impressively. Lots of B+...so much so that not many tubes live long in it.
A russian scientist explained that blue glow,i dont recall the name though..
When electrons move with speed multiple than light speed in vacuum space u see that blue glow.
The name was Nicola something
Cheers
When electrons move with speed multiple than light speed in vacuum space u see that blue glow.
The name was Nicola something
Cheers
Electrons can not move faster than light. Nothing moves faster than light.
Law of physics. Unlike human law, there is no arbitration phase, no appeals, no sentencing. When you break the laws of physics you go straight to the penalty phase.
If you hold a flashlight and turn it on, does the light move away from you at the speed of light? What happens when you hold two flashlights and point them in opposite directions?
Maybe Nicko_Lps was thinking of Cherenkov radiation. Cherenkov radiation occurs when electrons move in an insulator at a speed higher than the speed of light in that insulator. Which is of course possible. And it is a blueish glow in water. It can't occur in vacuum, obviously, for the reason Loren stated.
Kenneth
Kenneth
Great questions.
One thing you need to define is called the inertial frame of reference. This helps provide some guidance for understanding the problem.
In your example of two flashlights, neither set of photons are traveling faster than light, they are simply moving in opposite directions and the distance between the front wave of each photon packet will be twice the distance from each other than the distance from their origin to any one of the two packet wavefronts.
Let's look at this problem from another another perspective. Let's say Dave is on a spaceship moving at some velocity away from another object. A second person, John, on that object points a laser pen away from Dave (so that he doesn't blind the pilot, Nancy) in the direct opposite direction.
At what speed would the photons be traveling relative to John? The answer is C (C = the speed of light). That's easy.
At what speed would the photons from the laser be receding from the person on the spacecraft, Dave and Nancy? Again, it would still be the speed of light. It doesn't matter what velocity the spacecraft is moving, the answer is always C.
Why? Well first of all, velocity is distance divided by time.
We know by both theory and exhaustive experimentation that there is a relationship between time and velocity as well as time and gravity as predicted by Einstein. There are literally thousands of papers on the subject, so I won't attempt to rehash all of that.
For the individual on the spacecraft there will be a slight time dilation for him. Remember the twin paradox? William stays on Earth, but his twin brother Mark takes a quick trip to another star at near the speed of light and returns to find his brother is older than William? This is the predicted time dilation by Einstein.
Back to my example. From the perspective of the individual on the spacecraft the leading edge of the laser photon package is receding from him at a velocity of C. The reason is because Dave's (and Nancy's) on-board clock has slowed down just a little. So even though the distance between the receding photons of the laser pen is greater for Dave than it is for John, Dave and John are on different clocks and the formula for velocity is still distance over time.
For John, Dave and the laser photons are never moving faster than light, even though the distance between the laser photons and Dave is expanding faster than light would be able to travel. Does that make sense?
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Particles quite happily go faster than the local speed of light in a medium, like water. This is harder to do in vacuum! 🙂
Cherenkov radiation isn't at work here, because the energies are too low (300eV is a rather pedestrian 7.26 x 10^6 m/s, only 2.4% the speed of light -- you'd need an index of refraction around 41 to do it!).
Tim
Cherenkov radiation isn't at work here, because the energies are too low (300eV is a rather pedestrian 7.26 x 10^6 m/s, only 2.4% the speed of light -- you'd need an index of refraction around 41 to do it!).
Tim
I think you are right. The speed of photons through a medium such as water is about 75% of the speed of light through a vacuum.
I don't know of any medium which speeds up light, everything slows it down compared to a vacuum.
However, nothing prevents a particle from going faster than a photon when that photon is traveling through a medium other than a vacuum.
Exactly. And eventually it will lose enough speed by colliding with atom cores to stop emitting those Cherenkov photons. But exciting as it is, this is not what causes the blue glow in VT glass. As said earlier in this thread, the energies are too small. In normal materials it only occurs with energies associated with nuclear reactions (beta electron radiation).
Kenneth
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