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

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



.

Relevant Pages

  • Re: At power on tube filaments light up more than normal for a sec
    ... similar to the heater itself, in that it must have two ... some, many, or most do not flash on purpose. ... I have said that flashing is too ...
    (rec.audio.tubes)
  • Heater shining brightly
    ... After "cool" cathodes of an Electro-Harmonix 12AT7, ... The flash lasts for about 0.5 seconds. ... The flash occurs on applying heater voltage to a cold tube. ...
    (rec.audio.tubes)
  • Re: Heater shining brightly
    ... The flash lasts for about 0.5 seconds. ... Otherwise the tube ... The flash occurs on applying heater voltage to a cold ... making them dissipate more power per unit ...
    (rec.audio.tubes)
  • Re: Heater shining brightly
    ... Hetaer flash is normal with most Philips small signal tubes because of their ... The flash is caused by the inrush current to the low resistance of the ... before the cold heater warms. ... is applied to a tube heater. ...
    (rec.audio.tubes)
  • Re: The Observer: At last: lets put that rail crisis behind us
    ... the room is warm. ... What make of heater? ... "designer" had it taken out because it seems they didn't look flash ...
    (uk.railway)