Re: At power on tube filaments light up more than normal for a sec

flipper wrote:
On Mon, 08 Dec 2008 16:27:12 +0000, Ian Bell <ruffrecords@xxxxxxxxx>
wrote:

Arny Krueger wrote:
"flipper" <flipper@xxxxxxxx> wrote in message
news:tv2qj41a6c2vdveo579pelmeq8290fptfm@xxxxxxx

Well, I found this explanation.

http://reviews.ebay.com/Why-Mullard-Amperex-12AX7-flash-when-1st-energized_W0QQugidZ10000000002972031

That jives with what my first guess was. That a small bit
of filament was 'bare' while the rest is sort of
heatsinked inside the cathode section so the 'bare' part
flashes as the rest warms up slower. That would make it
just an artifact of their particular construction
technique.
Seem questionable:

"The "flash" is perfectly normal and it's a trademark characteristic of Mullard / Amperex tubes. There are a couple other brands that have a similar flash but I'll discuss Mullard / Amperex tubes specifically since they are my store specialty."

IME the flash was very common in the Japanese equipment that Lafayette used to import, back in the day of. Now, the Japanese may have been building tubes using Mullard/Amperex technology, but it was mostly the U.S. brand tubes that *didn't* flash.

"The flash occurs on one side of the filament wires between the bottom plate and the inside bottom of the tube and this phenomenon only occurs when powering up from a cold start. The sudden influx of current on the cold heater filament encounters very little resistance along this wire (hence the sudden burst of light). So in effect one side of the tube always warms up 1st, the second takes a while to catch up but before long the heat is evenly distributed (and your amp comes to life). "

Electricity flows at the speed of light,
<pedant>
Actually, in a conductor electricity does not 'flow at the speed of light' the net flow of electrons in a conductor is barely a few meters per second.
</pedant>

Cheers

Ian

This sounds like a fun game.


Yup.

Actually, that's only valid if you consider electrons, rather than the
EM field, to be 'electricity'.


There ain't no field without the electrons!

I would agree that the 'effect' of electron flow is much much quicker and close to the speed of light but the actual flow of electrons is far slower.

I rather think it's the EM field and if you dispute that then hold on
to the other end of this 5 meter cable while I stick 2KV on it for
'just a second'.

It's like a pipe full of water connected to a tap. As soon as you turn on the tap, water comes out the other end of the pipe (the effect) but the water at the tap at that moment takes a lot longer to reach the end of the pipe i.e. the 'flow, is much slowr.

Cheers

Ian
.

Relevant Pages

  • Re: At power on tube filaments light up more than normal for a sec
    ... Flow of electricity happens much faster than your surely quaint "net flow of electrons". ... "The "flash" is perfectly normal and it's a trademark characteristic of Mullard / Amperex tubes. ...
    (rec.audio.tubes)
  • Re: At power on tube filaments light up more than normal for a sec
    ... Flow of electricity happens much faster than ... light may be considered to flow at different speeds, ... characteristic of Mullard / Amperex tubes. ...
    (rec.audio.tubes)
  • Re: Hum, Ground Loops and Safety
    ... If you have two reservoirs of water, ... the blockage between those two conductors, the electricity will flow from ... Imagine that you have a very, very sharp butcher's cleaver, and several ...
    (alt.guitar.bass)
  • Re: microcontrollers under $50?
    ... a robot controller is something programmable, which can be used as the brain of a robot, and which is simple enough for me to use. ... has 16 pins of digital I/O and 7 of those pins can ... mysterious external widgets. ... purchasing a programmer than it is worth. ...
    (comp.robotics.misc)
  • Re: Wireless DC electricity?
    ... What if I want the flow of electricity to be only 1 electron wide? ... Any power supply that attempts to produce a voltage that is over the breakdown voltage of air has some major design problems. ... The voltage you cited is so extreme that, as you can see, it would require over 12 AU of separation between the positive and negative plates in order to prevent arc over. ... One limits current flow by having a large enough resistance across the power supply so as to limit the current flow from the supply. ...
    (sci.physics.research)
Loading