[Jack W]

Hi,

Yesterday I tried an old unused ecc82 tube made in 1960. When I powered on
my amp to standby, the tube lighted up for a bit more than it should, then
it went back to normal. Today I tried it again, and it did the same. I
wanted to see what's happening, so I powered off my amp, and back on again,
but it lighted up normal this time.
I waited for a while, then tried it again. It lighted up a bit more for a
second again. The light seems to be originating from the bottom of the tube,
where the pins are. Two of the pins are lighting up more brightly than
normal for a sec, then they die down.

My guess is that the tube is a bit leaky, and some oxygen has gotten in it.
When I power on the filaments, they light up more than normal for a bit
because of the oxygen, then they go back to normal.

Is that how it is, or is there some other reason? How bad is that for tube
life?

Many thanks for answers,

-Jack W

[Phil Allison]

"Jack W"

Yesterday I tried an old unused ecc82 tube made in 1960. When I powered on
my amp to standby, the tube lighted up for a bit more than it should, then
it went back to normal. Today I tried it again, and it did the same. I
wanted to see what's happening, so I powered off my amp, and back on
again, but it lighted up normal this time.
I waited for a while, then tried it again. It lighted up a bit more for a
second again. The light seems to be originating from the bottom of the
tube, where the pins are. Two of the pins are lighting up more brightly
than normal for a sec, then they die down.

My guess is that the tube is a bit leaky, and some oxygen has gotten in
it. When I power on the filaments, they light up more than normal for a
bit because of the oxygen, then they go back to normal.

Is that how it is, or is there some other reason? How bad is that for tube
life?

Many thanks for answers,


** Seen the visible part of heaters in twin triodes "flash" like that for
many decades.

It is just an interesting anomaly - not a real problem.

Like the fact that some power tubes glow blue in the dark.




..... Phil

[Patrick Turner]

Phil Allison wrote:

"Jack W"

Yesterday I tried an old unused ecc82 tube made in 1960. When I powered on
my amp to standby, the tube lighted up for a bit more than it should, then
it went back to normal. Today I tried it again, and it did the same. I
wanted to see what's happening, so I powered off my amp, and back on
again, but it lighted up normal this time.
I waited for a while, then tried it again. It lighted up a bit more for a
second again. The light seems to be originating from the bottom of the
tube, where the pins are. Two of the pins are lighting up more brightly
than normal for a sec, then they die down.

My guess is that the tube is a bit leaky, and some oxygen has gotten in
it. When I power on the filaments, they light up more than normal for a
bit because of the oxygen, then they go back to normal.

Is that how it is, or is there some other reason? How bad is that for tube
life?

Many thanks for answers,

** Seen the visible part of heaters in twin triodes "flash" like that for
many decades.

It is just an interesting anomaly - not a real problem.

Like the fact that some power tubes glow blue in the dark.

.... Phil

Twin triodes that flash at turn on are designed to do that because there
is a link of special wire in the tube which rapidly heats up at turn on
with the high input heater current when the heater current is high
because the heater filament is cold at turn on. Once the heater filament
current drops after it warms up the special link of wire drops in
temperature and resistance and allows the heater filament to run at
higher temperature with highy resistance. hence a large turn on surge of
filament power is avoided. Such surges are large when you have a lot of
tubes.

Patrick Turner.

[Phil Allison]

"Patrick Turneroid"

Phil Allison wrote:

"Jack W"

Yesterday I tried an old unused ecc82 tube made in 1960. When I powered
on
my amp to standby, the tube lighted up for a bit more than it should,
then
it went back to normal. Today I tried it again, and it did the same. I
wanted to see what's happening, so I powered off my amp, and back on
again, but it lighted up normal this time.
I waited for a while, then tried it again. It lighted up a bit more for
a
second again. The light seems to be originating from the bottom of the
tube, where the pins are. Two of the pins are lighting up more brightly
than normal for a sec, then they die down.

My guess is that the tube is a bit leaky, and some oxygen has gotten in
it. When I power on the filaments, they light up more than normal for a
bit because of the oxygen, then they go back to normal.

Is that how it is, or is there some other reason? How bad is that for
tube
life?

Many thanks for answers,

** Seen the visible part of heaters in twin triodes "flash" like that
for
many decades.

It is just an interesting anomaly - not a real problem.

Like the fact that some power tubes glow blue in the dark.

.... Phil

Twin triodes that flash at turn on are designed to do that because there
is a link of special wire in the tube ...


** Complete ********.

ROTFL



..... Phil

[Patrick Turner]

Phil Allison wrote:

"Patrick Turneroid"

Phil Allison wrote:

"Jack W"

Yesterday I tried an old unused ecc82 tube made in 1960. When I powered
on
my amp to standby, the tube lighted up for a bit more than it should,
then
it went back to normal. Today I tried it again, and it did the same. I
wanted to see what's happening, so I powered off my amp, and back on
again, but it lighted up normal this time.
I waited for a while, then tried it again. It lighted up a bit more for
a
second again. The light seems to be originating from the bottom of the
tube, where the pins are. Two of the pins are lighting up more brightly
than normal for a sec, then they die down.

My guess is that the tube is a bit leaky, and some oxygen has gotten in
it. When I power on the filaments, they light up more than normal for a
bit because of the oxygen, then they go back to normal.

Is that how it is, or is there some other reason? How bad is that for
tube
life?

Many thanks for answers,

** Seen the visible part of heaters in twin triodes "flash" like that
for
many decades.

It is just an interesting anomaly - not a real problem.

Like the fact that some power tubes glow blue in the dark.

.... Phil

Twin triodes that flash at turn on are designed to do that because there
is a link of special wire in the tube ...

** Complete ********.

ROTFL

.... Phil

Braying at the world with a statement such as "Complete ********" does
not demolish the validity of what I said.

You might like to further investigate the phenomena of flashing small
signal tube filamants at turn on.
Some flash and others of the same type number don't, and the flashers
have a different filament construction to those that don't flash.

There is a reason for the flashing behaviour.


Patrick Turner.

[Ian Iveson]

Phil whinged:

Twin triodes that flash at turn on are designed to do
that because there
is a link of special wire in the tube ...


** Complete ********.

ROTFL

Somehow, by using wires of different properties, or one wire
with a constriction, or by some other means, the heater must
have at least two component parts with different
thermo-electric properties, so one heats up quicker than the
other. Then the quick part glows bright until the slow part
gets hot and reduces the current.

So how do believe this is achieved?

Anyway, the OP only needs to know that the phenomenon is
deliberate, not a fault, and quite possibly occasion for
rejoicing.

Unlike glowing a benign shade of blue, which is generally
accidental or at least incidental, and doesn't matter one
way or the other.

Ian

[Phil Allison]

"Patrick Turneroid Sub Human"

Twin triodes that flash at turn on are designed to do that because
there
is a link of special wire in the tube ...

** Complete ********.

ROTFL


Braying at the world with a statement such as "Complete ********" does
not demolish the validity of what I said.


** It challenges YOU to come up with proof.

And you have not and cannot.


Some flash and others of the same type number don't, and the flashers
have a different filament construction to those that don't flash.


** Nope - same construction.

Just a bit of heater wire is left poking out the end of the cathode tube.

You ****wit bricklayer.

LOL !!!



...... Phil

[Phil Allison]

"Ian Iveson Congenital ****wit"
" The Turneroid Public Menace"

Twin triodes that flash at turn on are designed to do that because
thereis a link of special wire in the tube ...


** Complete ********.

ROTFL


Somehow, by using wires of different properties, or one wire with a
constriction, or by some other means, the heater must have at least two
component parts with different thermo-electric properties,


** Wot utter ******** !!


So how do believe this is achieved?


** Not the crazy way you just made up.




....... Phil

[Paul G.]

On Sun, 07 Dec 2008 06:31:56 -0600, flipper wrote:

On Sun, 7 Dec 2008 13:17:29 +0200, "Jack W" wrote:

Hi,

Yesterday I tried an old unused ecc82 tube made in 1960. When I powered on
my amp to standby, the tube lighted up for a bit more than it should, then
it went back to normal. Today I tried it again, and it did the same. I
wanted to see what's happening, so I powered off my amp, and back on again,
but it lighted up normal this time.
I waited for a while, then tried it again. It lighted up a bit more for a
second again. The light seems to be originating from the bottom of the tube,
where the pins are. Two of the pins are lighting up more brightly than
normal for a sec, then they die down.

My guess is that the tube is a bit leaky, and some oxygen has gotten in it.
When I power on the filaments, they light up more than normal for a bit
because of the oxygen, then they go back to normal.

Is that how it is, or is there some other reason? How bad is that for tube
life?

Many thanks for answers,

-Jack W


Some do it and some don't. In either case it's normal.

Remember, a cold filament has much lower resistance than when hot so a
current surge is to be expected. Whether it's just that more of the
filament is exposed and visible on the ones that 'flash', or if
there's an intentional mechanism at work, I don't know for sure.

Cold surge, btw, is why aging incandescent light bulbs tend to fail at
turn on. The inrush current is a stress on the increasingly fragile
filament.

Tube filaments, though, usually last longer than the tube because, as
their purpose is not to emit light, they are not operated at 'white
light' temperature.


I have been told that the tubes that are very bright when first
powered are "controlled warm-up time". These are usually variations of
a previously designed tube, such that the filament (and subsequently)
the cathode can reach a temperature suitable for electron emission,
within a specified time interval. It is quite probable that the heater
wires have a suitable temperature coefficient of resistance that
causes them to draw considerable current at warmup to help temporarily
pour on the power while warming up. I also suspect but haven't been
able to prove that the filament could be wired in two sections, where
one section is designed to give a high inrush current to the other
running filament. It would be the high-inrush section that glows
brightly.
Controlled warmup time was commonly used for series wired filaments,
it became necessary for all the tubes to warm up at roughly the same
time to distribute the filament voltage drops evenly, to allow circuit
functions to start at the same time (ie., avoiding power supplies
running overvoltage because there is no significant load yet), and to
avoid "cathode stripping" (if this is a real issue).
When servicing tube type TV's years ago, I noticed that certain
tubes would light up real bright, then die down to normal. The
intention of that controlled warmup was to get that circuit
functioning before other circuits became active.
The ECC82/12AU7A is a controlled warmup type (11 seconds). This is
normal for it to glow brightly for a second or so. I don't have the
big set of tube manuals that would give you more information comparing
warmup times of the non-controlled warmup types. Chances are that the
controlled warmup is a bit rougher on the filaments. Since loss of
emission is much more common than filament failure, the designers
figured users were not being overly compromised.

-Paul G.

[Ian Bell[_2_]]

flipper wrote:
On Mon, 08 Dec 2008 04:02:59 GMT, Paul G. wrote:

On Sun, 07 Dec 2008 06:31:56 -0600, flipper wrote:

On Sun, 7 Dec 2008 13:17:29 +0200, "Jack W" wrote:

Hi,

Yesterday I tried an old unused ecc82 tube made in 1960. When I powered on
my amp to standby, the tube lighted up for a bit more than it should, then
it went back to normal. Today I tried it again, and it did the same. I
wanted to see what's happening, so I powered off my amp, and back on again,
but it lighted up normal this time.
I waited for a while, then tried it again. It lighted up a bit more for a
second again. The light seems to be originating from the bottom of the tube,
where the pins are. Two of the pins are lighting up more brightly than
normal for a sec, then they die down.

My guess is that the tube is a bit leaky, and some oxygen has gotten in it.
When I power on the filaments, they light up more than normal for a bit
because of the oxygen, then they go back to normal.

Is that how it is, or is there some other reason? How bad is that for tube
life?

Many thanks for answers,

-Jack W

Some do it and some don't. In either case it's normal.

Remember, a cold filament has much lower resistance than when hot so a
current surge is to be expected. Whether it's just that more of the
filament is exposed and visible on the ones that 'flash', or if
there's an intentional mechanism at work, I don't know for sure.

Cold surge, btw, is why aging incandescent light bulbs tend to fail at
turn on. The inrush current is a stress on the increasingly fragile
filament.

Tube filaments, though, usually last longer than the tube because, as
their purpose is not to emit light, they are not operated at 'white
light' temperature.

I have been told that the tubes that are very bright when first
powered are "controlled warm-up time". These are usually variations of
a previously designed tube, such that the filament (and subsequently)
the cathode can reach a temperature suitable for electron emission,
within a specified time interval. It is quite probable that the heater
wires have a suitable temperature coefficient of resistance that
causes them to draw considerable current at warmup to help temporarily
pour on the power while warming up. I also suspect but haven't been
able to prove that the filament could be wired in two sections, where
one section is designed to give a high inrush current to the other
running filament. It would be the high-inrush section that glows
brightly.
Controlled warmup time was commonly used for series wired filaments,
it became necessary for all the tubes to warm up at roughly the same
time to distribute the filament voltage drops evenly, to allow circuit
functions to start at the same time (ie., avoiding power supplies
running overvoltage because there is no significant load yet), and to
avoid "cathode stripping" (if this is a real issue).
When servicing tube type TV's years ago, I noticed that certain
tubes would light up real bright, then die down to normal. The
intention of that controlled warmup was to get that circuit
functioning before other circuits became active.
The ECC82/12AU7A is a controlled warmup type (11 seconds). This is
normal for it to glow brightly for a second or so. I don't have the
big set of tube manuals that would give you more information comparing
warmup times of the non-controlled warmup types. Chances are that the
controlled warmup is a bit rougher on the filaments. Since loss of
emission is much more common than filament failure, the designers
figured users were not being overly compromised.

-Paul G.

Well, that all sounds logical but I have scads of controlled warm up
tubes that don't flash with my 6AW8 'PC Speaker' amp, both of them,
being an example in daily operation.

Of the ones in operating amps only one 12AX7 do da flash, but 12AX7s
are not controlled warm up. At least not according to my RCA, G.E.,
and Mullard datasheets.

I can't tell ya who made the one and only that does it because I could
barely read the 12AX7 marking when I first found it and, by now,
there's only a few flecks of that left.

My 12AU7s don't flash either but, according to my datasheets, it's
only the 7AU7, heaters in parallel for 3.5V, that's 'controlled
warmup'.

My controlled warm up 6FQ7/6CG7s don't flash either.

Just to add to the confusion, I have four 6FQ7 tubes, one flashes and
the other three don't.

Cheers

Ian

[Patrick Turner]

Phil Allison wrote:

"Patrick Turneroid Sub Human"

Twin triodes that flash at turn on are designed to do that because
there
is a link of special wire in the tube ...

** Complete ********.

ROTFL


Braying at the world with a statement such as "Complete ********" does
not demolish the validity of what I said.

** It challenges YOU to come up with proof.

And you have not and cannot.

And you have not proven me wrong.

So it challenges YOU to come up with proof.

Its not an issue of life and death and has been covered before at this
forum.

I am short of time and have more useful things to do than prove you
wrong this time.

Some flash and others of the same type number don't, and the flashers
have a different filament construction to those that don't flash.

** Nope - same construction.

Just a bit of heater wire is left poking out the end of the cathode tube.

So you say some heater filaments are left "poking out" and some are left
not "poking out".

So the construction *is different*

ASAIK, there isn't much in Google about it but I read the reason why
some tube flash some time ago.

May have something to do with "controlled warm up time"



You ****wit bricklayer.

I can and did lay bricks for a living during my days of being very
usefully and gainfully employed.

Not very often though because if there were more than a thousand to lay
I'd hire a sub-contractor.
This left me time to do all the other things involved with building a
house.

I hate to have to point out that apart from your encyclopeadic knowledge
of electronics,
you don't have very broad experience at a range of highly skilled trade
activities except electronics.

And you are not always correct.

I could call you a "****wit solderer", but I won't.

Patrick Turner.



LOL !!!

..... Phil

[Patrick Turner]

"Paul G." wrote:

On Sun, 07 Dec 2008 06:31:56 -0600, flipper wrote:

On Sun, 7 Dec 2008 13:17:29 +0200, "Jack W" wrote:

Hi,

Yesterday I tried an old unused ecc82 tube made in 1960. When I powered on
my amp to standby, the tube lighted up for a bit more than it should, then
it went back to normal. Today I tried it again, and it did the same. I
wanted to see what's happening, so I powered off my amp, and back on again,
but it lighted up normal this time.
I waited for a while, then tried it again. It lighted up a bit more for a
second again. The light seems to be originating from the bottom of the tube,
where the pins are. Two of the pins are lighting up more brightly than
normal for a sec, then they die down.

My guess is that the tube is a bit leaky, and some oxygen has gotten in it.
When I power on the filaments, they light up more than normal for a bit
because of the oxygen, then they go back to normal.

Is that how it is, or is there some other reason? How bad is that for tube
life?

Many thanks for answers,

-Jack W


Some do it and some don't. In either case it's normal.

Remember, a cold filament has much lower resistance than when hot so a
current surge is to be expected. Whether it's just that more of the
filament is exposed and visible on the ones that 'flash', or if
there's an intentional mechanism at work, I don't know for sure.

Cold surge, btw, is why aging incandescent light bulbs tend to fail at
turn on. The inrush current is a stress on the increasingly fragile
filament.

Tube filaments, though, usually last longer than the tube because, as
their purpose is not to emit light, they are not operated at 'white
light' temperature.

I have been told that the tubes that are very bright when first
powered are "controlled warm-up time". These are usually variations of
a previously designed tube, such that the filament (and subsequently)
the cathode can reach a temperature suitable for electron emission,
within a specified time interval. It is quite probable that the heater
wires have a suitable temperature coefficient of resistance that
causes them to draw considerable current at warmup to help temporarily
pour on the power while warming up. I also suspect but haven't been
able to prove that the filament could be wired in two sections, where
one section is designed to give a high inrush current to the other
running filament. It would be the high-inrush section that glows
brightly.
Controlled warmup time was commonly used for series wired filaments,
it became necessary for all the tubes to warm up at roughly the same
time to distribute the filament voltage drops evenly, to allow circuit
functions to start at the same time (ie., avoiding power supplies
running overvoltage because there is no significant load yet), and to
avoid "cathode stripping" (if this is a real issue).
When servicing tube type TV's years ago, I noticed that certain
tubes would light up real bright, then die down to normal. The
intention of that controlled warmup was to get that circuit
functioning before other circuits became active.
The ECC82/12AU7A is a controlled warmup type (11 seconds). This is
normal for it to glow brightly for a second or so. I don't have the
big set of tube manuals that would give you more information comparing
warmup times of the non-controlled warmup types. Chances are that the
controlled warmup is a bit rougher on the filaments. Since loss of
emission is much more common than filament failure, the designers
figured users were not being overly compromised.

-Paul G.

Your right about the controlled warm up time of 11 seconds being
incorporated as a feature to existing tubes which didn't have a
controlled warm up time.

Your other reasoning is a bit guessy for me to believe you. All I
thought was that there is a small section of series wire which quickly
flashes at turn on due to the inevitable heavy filament current when its
cold and low resistance. But as the filament current falls due to its
warm up and rise in resistance the current in the flasher lessens and
the flasher gets cool enough so it does not glow and its resistance
falls allowing the final current to settle up to the specified amount.

Phil A cannot prove I'm wrong, and I have not seen much in Google about
it. Maybe the previous discussions will reveal why the tubes flash.

Patrick Turner.

[Phil Allison]

"Patrick Turneroid Sub Human"


Twin triodes that flash at turn on are designed to do that because
there is a link of special wire in the tube ...

** Complete ********.

ROTFL


Braying at the world with a statement such as "Complete ********" does
not demolish the validity of what I said.

** It challenges YOU to come up with proof.

And you have not and cannot.

And you have not proven me wrong.


** Nothing whatsoever proves your mad idea right.


Some flash and others of the same type number don't, and the flashers
have a different filament construction to those that don't flash.

** Nope - same construction.

Just a bit of heater wire is left poking out the end of the cathode
tube.

So you say some heater filaments are left "poking out" and some are left
not "poking out".

So the construction *is different*


** Utterly brain dead Turneroid bull****.

You ****wit ASD ****ed bricklayer.




...... Phil

[Ian Iveson]

Phil Allison blustered:

So how do believe this is achieved?


** Not the crazy way you just made up.

Shush. Obviously you don't know.

Ian

[Arny Krueger]

"flipper" wrote in message


Well, I found this explanation.

http://reviews.ebay.com/Why-Mullard-...00000002972031

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, and the whole tube is in a vacuum.
The thermal intertia of the components the filament contacts would be a
possible variable. Most tubes that have separate and symmetrical sides are
are duals, and they seem to light up about the same. 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.

[Phil Allison]

"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

[Ian Iveson]

"Patrick Turner" wrote in message
...


Phil Allison wrote:

"Patrick Turneroid Sub Human"

Twin triodes that flash at turn on are designed to
do that because
there
is a link of special wire in the tube ...

** Complete ********.

ROTFL


Braying at the world with a statement such as "Complete
********" does
not demolish the validity of what I said.

** It challenges YOU to come up with proof.

And you have not and cannot.

And you have not proven me wrong.

So it challenges YOU to come up with proof.

Its not an issue of life and death and has been covered
before at this
forum.

I am short of time and have more useful things to do than
prove you
wrong this time.

Some flash and others of the same type number don't,
and the flashers
have a different filament construction to those that
don't flash.

** Nope - same construction.

Just a bit of heater wire is left poking out the end of
the cathode tube.

So you say some heater filaments are left "poking out" and
some are left
not "poking out".

So the construction *is different*


Yes, because that would be one way of dividing the heater
into two sections with different properties. The short
exposed section is not cooled by contact with the cold
cathode/heater insulation envelope at turn on, so it warms
up quicker and hogs the current until the surface of the
insulation gets hot. The delay would depend on the thermal
conductivity and specific heat of the insulation material.

Also, the exposed section does not contribute to the heating
of the cathode, which would warm up more slowly.

It is quite possible that several methods were used, but if
Phil's method works, then it is also possible that it could
happen accidentally to some valves in manufacture.

There used to be people here that knew this stuff, and yes,
those of us who have been here from those days know some
things without remembering why.

Ian

ASAIK, there isn't much in Google about it but I read the
reason why
some tube flash some time ago.

May have something to do with "controlled warm up time"



You ****wit bricklayer.

I can and did lay bricks for a living during my days of
being very
usefully and gainfully employed.

Not very often though because if there were more than a
thousand to lay
I'd hire a sub-contractor.
This left me time to do all the other things involved with
building a
house.

I hate to have to point out that apart from your
encyclopeadic knowledge
of electronics,
you don't have very broad experience at a range of highly
skilled trade
activities except electronics.

And you are not always correct.

I could call you a "****wit solderer", but I won't.

Patrick Turner.



LOL !!!

..... Phil

[Ian Iveson]

Flipper wrote:

Well, I found this explanation.

http://reviews.ebay.com/Why-Mullard-...00000002972031

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.

Thesis, antithesis, synthesis. Oh, yes! Nice to see a
positive result. Particularly because the argument is
similar to the heater itself, in that it must have two
components of different properties that eventually achieve
equilibrium.

That
would make it just an artifact of their particular
construction
technique.

Syntax, please! Do you mean it must be accidental, or that
it could be accidental sometimes, or am I on the wrong track
altogether?

Maybe my 'no label left' 12AX7 is an Amperex. For some
reason that
seems to ring a bell.

For me, too. Also, I have some Mazda-labelled 12AX7 that
flash. Can't see an exposed loop, but visibility is poor.

Ian

[Ian Bell[_2_]]

Arny Krueger wrote:
"flipper" wrote in message


Well, I found this explanation.

http://reviews.ebay.com/Why-Mullard-...00000002972031

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

[Ian Iveson]

flipper wrote:

Thesis, antithesis, synthesis. Oh, yes! Nice to see a
positive result. Particularly because the argument is
similar to the heater itself, in that it must have two
components of different properties that eventually achieve
equilibrium.

I take it you mean that to be a humorous 'tubie' version
of the Mad
Hatter or something.

Dialectics again. Find out or ignore, I don't mind which.

That
would make it just an artifact of their particular
construction
technique.

Syntax, please!

Most people don't like to have their sins taxed.

The sentence. on the other hand, is fine.

The "just" is of questionable value with respect to meaning,
but I won't dwell on it.

If the syntax is good, then your logic is clearly at fault.
Just because some flash accidentally does not mean that
some, many, or most do not flash on purpose.

I contend that most of our experiences suggest that mostly
it happens on purpose.

I don't see a range of flashing, resulting randomly or
normally from a range of accidents, but rather I see some
valves that flash very obviously, and most that don't flash
at all. That's why flashing is remarkable.

It could be that there are several accepted and adopted
methods of construction, one of which accidentally results
in flashing, but that seems less likely to be true than the
assumption that it is a deliberate feature, with a purpose.

Controlling warm-up time over several seconds is not the
purpose, because the flash is too brief to make enough
difference. One purpose could be to reduce the mechanical
and thermal shock to the heater/cathode insulation,
considering that is a more likely source of failure than
heater fracture. Or it could be that the combination of
physical constraint to movement resulting from a jacket of
insulation, and rapid thermal expansion, is much more likely
to fracture the heater than either of those circumstances
alone. Leaving a loose length that takes the thermal shock
without the physical constraint would then reduce the risk
of heater fracture.

Anyway, I don't buy the accident argument so far. I know
that some afficianados regard flashing as a desirable
quality. They may be daft, but I'm not convinced they're
completely stupid.

Ian

Do you mean it must be accidental, or that
it could be accidental sometimes, or am I on the wrong
track
altogether?

'Accidental' implies there's something 'wrong' with it but
you're on
the right track.

What I mean is it isn't there to control warmup, limit
surge, or any
of the other logical, but apparently invalid,
suppositions.

There is a 'reason', of course, but it involves how they
decided to
construct the heater assembly and, hey, lookie there. it
also results
in a visible flash but so what, doesn't matter, who cares?
I.E. it's
an artifact, like the 'shiny stuff' is an artifact of the
getter. It
just turns out that way, not because they thought it would
look kewl.
Nor is it an 'electrostatic shield', sun shade, or
whatever clever
theory one's imagination might devise trying to explain
why they made
it shiny.

I came to that conclusion after pulling up the 1962 RCA
Electron Tube
Design manual, which is a collection of technical papers
going into
everything you ever wanted to know and thrice as many you
never
thought to ask.

Went to the section on how to make heaters do whatever you
want, what
not to do, and all the things that can go wrong and why.
And in the
section on heater warm up there was not one mention of an
extra,
separate, thingamabob to make things come out right, Or
control surge,
or anything else, much less one that goes Gremlins bright
light,
bright light, at turn on.

One of the primary means to control warm up time is the
heater
insulation coating. Thicker layer, more mass, slower time,
etc.

Now, I've only got one 'flasher' to look at but I compared
it to the
other 12AX7 in the amp and, by golly, the insulation layer
on it's
filament wire does *not* go all the way to the pin weld.
It does on
the 'non flasher'. And that exposed section of filament is
where the
flash is coming from.



Maybe my 'no label left' 12AX7 is an Amperex. For some
reason that
seems to ring a bell.

For me, too. Also, I have some Mazda-labelled 12AX7 that
flash. Can't see an exposed loop, but visibility is poor.

Ian

[Ian Iveson]

Ian wrote:

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.

Two different things, depending on what you think
electricity is. Flow of electricity happens much faster than
your surely quaint "net flow of electrons".

Speed of light is not a great help, either, considering
light may be considered to flow at different speeds, and
doesn't flow at all in a heater wire.

Arny would have been better off just saying it's really
fast, or near-as-dammit instantaneous, and leave light out
of it altogether.

There is something in what he says, in that "thermal
inertia" cannot alone explain flashing. For a one-part
heater, electrical inertia would be necessary, such as a
choke. Since it happens without a choke or other source of
electrical delay, there must be two parts to the heater.

Ian

"Ian Bell" wrote in message
...
Arny Krueger wrote:
"flipper" wrote in message


Well, I found this explanation.

http://reviews.ebay.com/Why-Mullard-...00000002972031

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
/pedant

Cheers

Ian

[Jan]

Flashing heaters, another reason to go solid state.

Jan

[Ian Bell[_2_]]

flipper wrote:
On Mon, 08 Dec 2008 16:27:12 +0000, Ian Bell
wrote:

Arny Krueger wrote:
"flipper" wrote in message


Well, I found this explanation.

http://reviews.ebay.com/Why-Mullard-...00000002972031

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

[Ian Bell[_2_]]

Ian Iveson wrote:
Ian wrote:

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.

Two different things, depending on what you think
electricity is. Flow of electricity happens much faster than
your surely quaint "net flow of electrons".


Of course, hence the ,pedant/pedant tokens.

Speed of light is not a great help, either, considering
light may be considered to flow at different speeds, and
doesn't flow at all in a heater wire.


Personally I am uncomfortable with the term 'flow' applied to light.

Arny would have been better off just saying it's really
fast, or near-as-dammit instantaneous, and leave light out
of it altogether.


Indeed.

There is something in what he says, in that "thermal
inertia" cannot alone explain flashing. For a one-part
heater, electrical inertia would be necessary, such as a
choke. Since it happens without a choke or other source of
electrical delay, there must be two parts to the heater.


Quite possibly.

Cheers

Ian
Ian

"Ian Bell" wrote in message
...
Arny Krueger wrote:
"flipper" wrote in message


Well, I found this explanation.

http://reviews.ebay.com/Why-Mullard-...00000002972031

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
/pedant
Cheers

Ian

[Phil Allison]

"flipper"
Ian Bell

Electricity flows at the speed of light,

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.


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 didn't say there was.


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.

And I suggested that the 'effect' is what's meant by 'electricity'.


** Wot about " static electricity " ??

Surely that ain't going anywheres .......




.... Phil

[Paul G.]

On Mon, 08 Dec 2008 11:43:38 GMT, Patrick Turner
wrote:



Your right about the controlled warm up time of 11 seconds being
incorporated as a feature to existing tubes which didn't have a
controlled warm up time.

Your other reasoning is a bit guessy for me to believe you. All I
thought was that there is a small section of series wire which quickly
flashes at turn on due to the inevitable heavy filament current when its
cold and low resistance. But as the filament current falls due to its
warm up and rise in resistance the current in the flasher lessens and
the flasher gets cool enough so it does not glow and its resistance
falls allowing the final current to settle up to the specified amount.

Phil A cannot prove I'm wrong, and I have not seen much in Google about
it. Maybe the previous discussions will reveal why the tubes flash.


I had thought of that explanation myself, but dismissed it because
most lamps have the same positive tempco of resistance, ie., they have
low resistance when cold and not powered, but have much higher
resistance when glowing bright. These devices and PTC thermistors will
heat up and establish an equilibrium current. They do not overshoot
(get real bright, or extra hot, then settle down to a moderate
brightness). They WILL draw considerable current while they are cold.

The only time I have seen such overshoot is when you have a thermal
feedback (gasp!) and there is a delay between sensor and heater, or
you have a kind of "feedforward" system whereby you select an inrush
time constant that gives a faster system response time.

That's why I suggested that there are two sections, one that has the
high inrush to help shorten the warmup time, and the other section is
the ordinary part of the filament.

The only way to tell is to smash open a 12AX7 and 12AX7A (same mfr.,
and not too far apart in time) and compare the differences.

This site suggests the 12AX7A runs lower temperatu
http://www.diytube.com/phpBB2/viewto...63eb2 d210691
If you search using 12AX7, 12AX7A, "controlled warm up" you should
find a number of articles relating to this behaviour. Apparently,
according to those articles, there are brands (Philips/Mullard) that
exhibit this behaviour, while RCA tubes don't.

Something that helps explain the reason for controlled warmup times:
A quotation from:
http://www.w8ji.com/vacuum_tubes_and...e_failures.htm
------start of quotation-------
"Positive ions are formed through ionization of residual gasses. High
anode voltages speed formation of positive ions. The space charge
(electron cloud) surrounding the cathode repels positive ions, and
keeps the ions from poisoning the cathode. When positive ions
contaminate the cathode, electron emission is reduced.

Tungsten has the highest melting temperature of any metal, above
3600K. Tungsten has the ability to operate at high temperatures for
many hours without evaporation of materials becoming a major problem.
Tungsten is one of the few materials able to withstand total depletion
of the electron cloud in a vacuum tube. Tungsten emitters are not
damaged by stripping away of electron clouds, and the resulting
cathode bombardment by positive ions. This immunity to damage means
emission life is not shortened by excessive current, operation before
full temperature is reached, or low filament voltage.

If a cathode material sensitive to positive ions is operated with
excessive HV, or has excessive cathode current for the cathode
operating temperature, it will suffer emission failure. This is why
indirectly-heated tubes or oxide-cathode tubes must have long
controlled warm-up times before any cathode current is drawn. We must
NEVER operate the 3CX1500A7/ 8877, 3CX800A7, or other oxide-cathode
tubes at reduced heater voltage! This would allow the cathode's
protective electron cloud to be depleted, and nothing would prevent
positive ions from striking and poisoning the cathode. "
---end of quototation-----



-Paul G.

[Phil Allison]

"Paul G."


That's why I suggested that there are two sections, one that has the
high inrush to help shorten the warmup time, and the other section is
the ordinary part of the filament.


** Completely daft.

You totally fail to comprehend how a tungsten filament wire will behave when
a small part of it has a much shorter thermal time constant that the rest -
due to the fact it is exposed above or below the cathode tube structure.

Remember - at all times, the current flow is the SAME in all parts of the
filament wire, cos it is all just one circuit.

Plus - the ratio of initial to final current value for typical tube
heaters is about 6:1 while the time to reach final temp is about 10 to 15
seconds. The initial power draw is also 6 times more than what it becomes
later - because the current draw and total filament resistance are
inversely proportional.

Due to this * 6 times* extra current in the first second - a small, fast
heating part of the filament will briefly dissipate at least 6 times more
heat than it does later when the current settles down to nominal value.
However, because it IS fast heating and it IS exposed ( unlike the rest
of the filament) the high dissipation makes it visibly "flash".

End of story.



...... Phil

[Phil Allison]

"flip top head "


And I suggested that the 'effect' is what's meant by 'electricity'.


** Wot about " static electricity " ??

Wot about it?


Surely that ain't going anywheres .......

Perhaps that's what "static" means.



** Wot a boring, literal ****wit.

Yawwnnnnnnnnnn.....




...... Phil

[Patrick Turner]

Phil Allison wrote:

"Patrick Turneroid Sub Human"


Twin triodes that flash at turn on are designed to do that because
there is a link of special wire in the tube ...

** Complete ********.

ROTFL


Braying at the world with a statement such as "Complete ********" does
not demolish the validity of what I said.

** It challenges YOU to come up with proof.

And you have not and cannot.

And you have not proven me wrong.

** Nothing whatsoever proves your mad idea right.

Some flash and others of the same type number don't, and the flashers
have a different filament construction to those that don't flash.

** Nope - same construction.

Just a bit of heater wire is left poking out the end of the cathode
tube.

So you say some heater filaments are left "poking out" and some are left
not "poking out".

So the construction *is different*

** Utterly brain dead Turneroid bull****.

You ****wit ASD ****ed bricklayer.

..... Phil

Nothing you have said has led members of the reading public towards a
better understanding of tube behaviour.

You resort to calling me names such as a ****wit bricklayer.

I was proud to lay bricks and work on building sites.

I made the world better by my efforts.

You bring awareness of my previous profession to the public.

You seem to think I'd be embarrassed to be called some kind of
bricklayer, but you are merely raising the public awareness of my
constructive life before transfering my competency from building to
electronics.

Its that time of year again Phil, time to remember to take your
medication for your bi-polar disorder.

You just can't stand someone cool like me who has the courage to
question all you say, and point out your argument deficiencies.

You'd do much better to take a close look at a vacuum tube to see
exactly why it flashes.

Maybe gently crack one open and examine it.

A little destructive forensic might be constructively informative
instead of typing bull**** personal assessments.

Patrick Turner.

[Patrick Turner]

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.

I quote.......

""""My Mullard / Amperex 12AX7 ECC83 makes a brilliant flash when the
amp is turned on - is this a bad tube?

Nope - 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.

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).

Turn off your amp - and restart it again. You won't see the same flash
if the tubes are still hot - it only happens on cold startup.""""

End of quote

Patrick Turner.

[Patrick Turner]

Phil Allison wrote:

"Paul G."

That's why I suggested that there are two sections, one that has the
high inrush to help shorten the warmup time, and the other section is
the ordinary part of the filament.

** Completely daft.

You totally fail to comprehend how a tungsten filament wire will behave when
a small part of it has a much shorter thermal time constant that the rest -
due to the fact it is exposed above or below the cathode tube structure.

Remember - at all times, the current flow is the SAME in all parts of the
filament wire, cos it is all just one circuit.

Plus - the ratio of initial to final current value for typical tube
heaters is about 6:1 while the time to reach final temp is about 10 to 15
seconds. The initial power draw is also 6 times more than what it becomes
later - because the current draw and total filament resistance are
inversely proportional.

Due to this * 6 times* extra current in the first second - a small, fast
heating part of the filament will briefly dissipate at least 6 times more
heat than it does later when the current settles down to nominal value.
However, because it IS fast heating and it IS exposed ( unlike the rest
of the filament) the high dissipation makes it visibly "flash".

End of story.

..... Phil

Are yes Phil, but it ain't the end of the story.

Sure, the current is always the same in whatever heating wire is in
there. Its what I said. But if they deliberately leave some portion of
heater wire exposed so its heat doesn't dissipate into the cathode
structure from turn on, sure, that exposed wire gets hotter than the
rest of the enclosed wire. Its *different construction* to build a
cathode structure this way than having all the heating wire enclosed to
make sure all of it dissipates its heat evenly. YOU denied there was any
difference, and led the public astray by posting bull****, so shut up
and learn something.

I said there was a special extra link of wire added in series to the
heater filament.
Nobody has proved this technique was not used sometimes. I have not
proved it was.
No need for references to bricklayers.

You shouldn't speak dis-respectfully about bricklayers. One might arrive
at your door and lay a ****ing brick right up your brown arsole.

If you have an old electronic organ with 72 oscillators each with a
12AX7 then you do need considerable start up current when heaters are
cold and you want to use a useful value of fuse. so there was some
interest in developing ways to build tubes differently to lessen the
inrush current, or reduce the time the high inrush current lasted until
things warmed up.


Patrick Turner.

[Patrick Turner]

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. 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.

Patrick Turner.


I quote.......

""""My Mullard / Amperex 12AX7 ECC83 makes a brilliant flash when the
amp is turned on - is this a bad tube?

Nope - 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.

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).

Turn off your amp - and restart it again. You won't see the same flash
if the tubes are still hot - it only happens on cold startup.""""

End of quote

Patrick Turner.

[Ian Bell[_2_]]

Phil Allison wrote:
"flipper"
Ian Bell
Electricity flows at the speed of light,
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.

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 didn't say there was.


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.
And I suggested that the 'effect' is what's meant by 'electricity'.


** Wot about " static electricity " ??

Surely that ain't going anywheres .......




... Phil




Nice one, Phil ;-)

Cheers

Ian

[Arny Krueger]

"flipper" wrote in message


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.

I think that's exactly what's happening.

It begs the question why it doesn't happen with *all* tubes, just certain
ones.

[Ian Iveson]

flipper wrote

Ian wrote:

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.

Two different things, depending on what you think
electricity is. Flow of electricity happens much faster
than
your surely quaint "net flow of electrons".

Speed of light is not a great help, either, considering
light may be considered to flow at different speeds, and
doesn't flow at all in a heater wire.

Arny would have been better off just saying it's really
fast, or near-as-dammit instantaneous, and leave light out
of it altogether.

There is something in what he says, in that "thermal
inertia" cannot alone explain flashing.

Of course it can.

No it can't, for a one-part heater.

For a one-part
heater,

Depending on what you 'mean', it isn't "one part." It is
'one part'
wire and "one part" insulation, just for starters.

That not the nub of the issue. The important point is that
there is one section of heater in contact with, a material
of high thermal conductivity, and one part that is in
contact with nothing, so must rely on radiation to loose its
heat.

electrical inertia would be necessary, such as a
choke.

nope.

Yes. Demonstrate how, using a one-part heater, "thermal
inertia" alone can lead to flashing.

Since it happens without a choke or other source of
electrical delay, there must be two parts to the heater.

There is the 'part' that's covered by insulation and the
'part' that
isn't. There's the 'part' that's in thermal proximity to a
big
heatsink called the cathode and the 'part' that isn't.

Now you've got the point, I hope. Why the inverted commas?
You appear at once to be denying and accepting that there
are two parts, and that seems like wriggling. I could
understand had I used "component", but I steered clear of
that, hoping you would see that a single heater can have two
parts.

If the flash takes only a second or so, as with my flashers,
then it is not the cathode that cools one part, but the
electrical insulation between heater and cathode, which has
high thermal conductivity (alumina?). The

Ian

[Ian Iveson]

flipper wrote:

Thesis, antithesis, synthesis. Oh, yes! Nice to see a
positive result. Particularly because the argument is
similar to the heater itself, in that it must have two
components of different properties that eventually
achieve
equilibrium.

I take it you mean that to be a humorous 'tubie' version
of the Mad
Hatter or something.

Dialectics again. Find out or ignore, I don't mind which.

I know what a dialectic is

:-)

but if you meant for the above to mean
something then you should say so.

Don't be daft. How would I do that? Should I write "this
means something" after everything I write? To anyone
aquainted with the dialectic, my meaning is obvious,
although my sense of humour may appear shallow. It was a
wink to the knowledgeable. You may ignore it, as I
suggested.

That
would make it just an artifact of their particular
construction
technique.

Syntax, please!

Most people don't like to have their sins taxed.

The sentence. on the other hand, is fine.

The "just" is of questionable value with respect to
meaning,
but I won't dwell on it.

In that context 'just' means "no more than" and that is
precisely what
was meant.

OK. In which case the logic is at fault.

If the syntax is good, then your logic is clearly at
fault.

No, the logic is perfectly fine.

No it isn't, not by a very long way.

Just because some flash accidentally

I already dealt with the 'accidentally' misconception so
why do you
repeat it?

does not mean that
some, many, or most do not flash on purpose.

You are working 'backwards'. You see a 'flash' and presume
there must
be some ' grand purpose' to it.

Rubbish. It is not an assumption, but a deduction, and I
accept it may be false. But you are wriggling. The point I
made here is that just because some flash by accident does
not mean that others do not flash on purpose. That is your
logical error, and it is very obvious. I am saying I believe
it is often deliberate. It is you who are so certain, on the
basis of scant evidence. So much so that you think you can
take the **** out of anyone who disagrees. Foolish
arrogance, I'm afraid.

The very point I made was there is no 'grand purpose' to
the 'flash;,
That it's simply an artifact of some other purpose, just
as there is
no 'grand purpose' to making the tops of miniature tubes
'shiny'. It's
simply an artifact of the gettering.

There you go again. No-one is saying the purpose is grand.

I contend that most of our experiences suggest that mostly
it happens on purpose.

All evidence suggests exactly the opposite because the
'flash vs 'non
flash' observations do not meet the terms of the
hypothesis. I.E. most
controlled warmup heaters do *not* flash wile various non
controlled
heaters *do*.

Eh? I haven't said the purpose is "controlled warmup". That
was a tentative suggestion by Patrick. You have subsequently
set it up as an aunt sally. I have said that flashing is too
quick to serve that purpose. I have suggested other possible
and plausible purposes related to reliability. But I don't
need to know the purpose to contend that flashing as a
phenomenon that has characteristics that may reasonably
associated with purpose. Purpose appears to me a more sound
assumption than no purpose.

I don't see a range of flashing, resulting randomly or
normally from a range of accidents, but rather I see some
valves that flash very obviously, and most that don't
flash
at all. That's why flashing is remarkable.

Now your just being silly. No one said it was 'random' or
'intermittent'.

Intermittent is presumably another deliberate red herring.

No, you didn't say it was random. I am saying that it does
not appear to be random or normal. I hoped you might see the
point I am making, in that one might expect accidental
things to be randomly or normally distributed. In either
case one might expect a range of flashing...as in some flash
a bit, some a lot, and many in between.

It could be that there are several accepted and adopted
methods of construction, one of which accidentally results
in flashing,

It's not an 'accident'.

Stop it. My meaning is clear. I mean that in that case it
would have no purpose. Not on purpose, accidental...see the
link?

You have been saying that flashing has no purpose,
vociferously despite lack of evidence. Are you now saying it
is has purpose?

but that seems less likely to be true than the
assumption that it is a deliberate feature, with a
purpose.

Nonsense.

Eh? Now what's nonsense? Is it nonsense that it seems less
likely to me?

The only reason it seems 'likely' to you is, for some
unknown reason,
you attach mystical significance to a flash of light.

Where did that come from? The significance I attach only
appears mystical to you because you have failed to
understand a word I have written about it.

Controlling warm-up time over several seconds is not the
purpose, because the flash is too brief to make enough
difference. One purpose could be to reduce the mechanical
and thermal shock to the heater/cathode insulation,
considering that is a more likely source of failure than
heater fracture. Or it could be that the combination of
physical constraint to movement resulting from a jacket of
insulation, and rapid thermal expansion, is much more
likely
to fracture the heater than either of those circumstances
alone. Leaving a loose length that takes the thermal shock
without the physical constraint would then reduce the risk
of heater fracture.

Since you're going to dream up things why not speculate
it's there to
scare Martians?

Here's a radical thought. How about doing some research
and *looking*
at one like I did?

I doubt there are any Martians, and don't believe you have
looked at one.

Anyway, I don't buy the accident argument so far. I know
that some afficianados regard flashing as a desirable
quality. They may be daft, but I'm not convinced they're
completely stupid.

Same folks that use magic pebbles, no doubt.

Absolutely not. There used to be some very knowledgeable
engineers here who knew their valves, unlike the clueless
technicians who have recently congregated.

Ian

[Ian Iveson]

Patrick Turner wrote

Phil Allison wrote:

"Paul G."

That's why I suggested that there are two sections, one
that has the
high inrush to help shorten the warmup time, and the
other section is
the ordinary part of the filament.

** Completely daft.

You totally fail to comprehend how a tungsten filament
wire will behave when
a small part of it has a much shorter thermal time
constant that the rest -
due to the fact it is exposed above or below the cathode
tube structure.

Remember - at all times, the current flow is the SAME
in all parts of the
filament wire, cos it is all just one circuit.

Plus - the ratio of initial to final current value for
typical tube
heaters is about 6:1 while the time to reach final temp
is about 10 to 15
seconds. The initial power draw is also 6 times more than
what it becomes
later - because the current draw and total filament
resistance are
inversely proportional.

Due to this * 6 times* extra current in the first
econd - a small, fast
heating part of the filament will briefly dissipate at
least 6 times more
heat than it does later when the current settles down to
nominal value.
However, because it IS fast heating and it IS exposed
( unlike the rest
of the filament) the high dissipation makes it visibly
"flash".

End of story.

..... Phil

Are yes Phil, but it ain't the end of the story.

Sure, the current is always the same in whatever heating
wire is in
there. Its what I said. But if they deliberately leave
some portion of
heater wire exposed so its heat doesn't dissipate into the
cathode
structure from turn on, sure, that exposed wire gets
hotter than the
rest of the enclosed wire. Its *different construction* to
build a
cathode structure this way than having all the heating
wire enclosed to
make sure all of it dissipates its heat evenly. YOU denied
there was any
difference, and led the public astray by posting bull****,
so shut up
and learn something.

I said there was a special extra link of wire added in
series to the
heater filament.
Nobody has proved this technique was not used sometimes. I
have not
proved it was.
No need for references to bricklayers.

And Phil has accepted that there is a special extra link of
wire. You don't disagree. The special extra link is a
section of heater wire not enclosed by the heater/cathode
insulation. It is extra because it contributes nothing to
the heating of the cathode, and it is special because it has
different characteristics from the section that does heat
the cathode. It is left loose therefore solely for the
purpose, or accident, of flashing.

None of which excludes the possibility that there were other
ways of arranging for a special extra link.

Ian

[Patrick Turner]

flipper wrote:

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

Thus that wire portion rises in T very quickly and lengthens the time it
takes to heat the cathode.
The inrush current very quickly reduces as it does with a lamp filament
turning on.

Patrick Turner.

[Ian Iveson]

Ian Bell wrote

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.

Two different things, depending on what you think
electricity is. Flow of electricity happens much faster
than your surely quaint "net flow of electrons".


Of course, hence the ,pedant/pedant tokens.


Sorry. Sometimes I fall prey to the temptation to be clever.
Actually I know sod all about electricity. I lost the plot
after the Bohr atom. These days I think of standing waves,
but not very clearly. Being a materialist, I have some
issues with explanations that place probability in the real
world.

The question "What is electricity?" is problematic, to say
the least.

cheers,

Ian

[Ian Iveson]

"Patrick Turner" wrote in message
...


flipper wrote:

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

Thus that wire portion rises in T very quickly and
lengthens the time it
takes to heat the cathode.
The inrush current very quickly reduces as it does with a
lamp filament
turning on.

As quick as the wire heats, in the sense that there is no
significant delay, hence filament bulbs don't flash,
usually.

Ian