[Ian Iveson]

"flipper" wrote in message
...
On Tue, 09 Dec 2008 09:14:29 GMT, Patrick Turner
wrote:



flipper wrote:

On Tue, 09 Dec 2008 07:19:16 GMT, Patrick Turner
wrote:



Phil Allison wrote:

"Arny Krueger"

Electricity flows at the speed of light,

** ROTFL !!

But heat travels down a wire at the speed of a sick
snail.

and the whole tube is in a vacuum.

** Yeah - vacuums are real *******s, they really
suck.

The thermal intertia of the components the filament
contacts would be a
possible variable.

** Hey - no fooling.

Amazing how everyone has already thought of that
!!!!

Most tubes that have separate and symmetrical sides
are are duals, and
they seem to light up about the same.

** My god - that is an inspired insight ......

There might be far less flash at the tops of tubes
because the filament
wires are just barely poking out, while the ones at
the bottom run all the
way down to the pins.

** IME - there are those that are " top flashers "
and there are those
that are " bottom flashers ".

And I am speaking of tubes, not people.

...... Phil


Phil, looks like I was right.

Not quite. I posted the same quote and while it's
probably sufficient
to allay the concerns of a home user it's not
technically correct.

For example, the description that "So in effect one side
of the
tube always warms up 1st" makes no sense.

It also seems he got a bit confused with the heater
wiring. Remember,
a 12AX7 has a center tapped heater and it appears to me
that he
confused the two going to pins 4 and 5 as 'one side'
with the one
going to pin 9 as the 'other side'.

At any rate, I did look at mine and it's simply that the
insulation
doesn't extend all the way to the pin weld so a portion
of the bare
filament is exposed.

His explanation for the flash is also incomplete. It
isn't just the
"very little resistance." It's the lower thermal mass of
the
uninsulated segment that warms faster than the rest so
it's resistance
increases faster and causes more voltage drop across it,
increasing
the power dissipated in that segment, till the remainder
of the heater
warms to operating temperature.

I seriously doubt that 50-75 mils out of the entire
heater length has
a significant effect on the overall surge and the
instantaneous
initial peak would still be the same since the 'whole
thing' starts
off cold.

The surge lasts a much shorter time if part of the heater
or an
additional link installed is allowed to glow like a lamp
filament at
turn on.

Actually, if it had any effect, which is doubtful because
of the
minuscule section affected, the surge would last longer
because it
would 'limit' (sic) the power input, so the rest would
take longer to
heat.

Just what the makers did to get the flash is not clear
until
someone provides evidence of exactly how it was done. I
suggest someone
smash open an old flasher and see what's inside. I'm too
busy with
orders for new amplifiers.

I already told you I *looked* and it's nothing more than
the last few
mills of the heater wire having no insulation.

Which illustrates the danger of allowing a hypothesis to
inform an observation, rather than vice-versa.

If Patrick's initial answer were correct, and if there is a
seperate link of special wire in series with the heater,
then it could look just like you have seen. What you can not
see by your inspection is your "nothing more than".

How do you know that the rest of the heater wire is the same
as what you see? How do you know that you are not looking at
the "special link"?

I am quite happy to accept that some flashers depend on an
exposed length of heater wire which is otherwise identical
to and continuous with the rest. But not on the basis of
your woefully inadequate observations.

And to establish that they are *all* like that would take
more than observation, practically. You would need
intelligence.

Ian