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Heater shining brightly
Heater shining brightly
Hello.
After "cool" cathodes of an Electro-Harmonix 12AT7, after glowing screen
grid of a Sovtek EL84 I came across another weird phenomenon.
When I power up a Philips Miniwatt 12AX7 (made in Australia) the tips of
its heater filaments, the ends, sticking out from the bottom of the cathodes
and going to the pins 4, 5 and 9, give out a flash of bright light, nearly
like of an incandescent globe.
The flash lasts for about 0.5 seconds. Then the light dimms, and eventually
turns into a "normal" red-orange when the valve warms up. Otherwise the tube
is OK with negligible heater-cathode leakage. Both triodes behave exactly
the same.
The flash occurs on applying heater voltage to a cold tube. If the tube has
alresdy been warmed up, switching heater voltage off and then on again does
not cause the flash.
My explanation is the following. While the heater is cold its resistance can
be as much as 5 times lower the nominal value. On power-up the current is
high. the tips of the heater wire, which are not in the [thermal] contact
with a massive cathode, tend to warm up quicker. Their resistance increases
faster locally, making them dissipate more power per unit length, which in
turn results in more local rise of the resistance, and more dissipation. It
is sort of an avalanche runaway process.
I have never come across such a phenomenon before, at least among Soviet
tubes. Always the glow was increasing gradually. I have never seen such a
heater flash.
I am wondering if it OK to have such a flash, or should this tube considered
faulty, or is it just a bad tube design, or what?
Regards,
Alex
Hello.
After "cool" cathodes of an Electro-Harmonix 12AT7, after glowing screen
grid of a Sovtek EL84 I came across another weird phenomenon.
When I power up a Philips Miniwatt 12AX7 (made in Australia) the tips of
its heater filaments, the ends, sticking out from the bottom of the cathodes
and going to the pins 4, 5 and 9, give out a flash of bright light, nearly
like of an incandescent globe.
The flash lasts for about 0.5 seconds. Then the light dimms, and eventually
turns into a "normal" red-orange when the valve warms up. Otherwise the tube
is OK with negligible heater-cathode leakage. Both triodes behave exactly
the same.
The flash occurs on applying heater voltage to a cold tube. If the tube has
alresdy been warmed up, switching heater voltage off and then on again does
not cause the flash.
My explanation is the following. While the heater is cold its resistance can
be as much as 5 times lower the nominal value. On power-up the current is
high. the tips of the heater wire, which are not in the [thermal] contact
with a massive cathode, tend to warm up quicker. Their resistance increases
faster locally, making them dissipate more power per unit length, which in
turn results in more local rise of the resistance, and more dissipation. It
is sort of an avalanche runaway process.
I have never come across such a phenomenon before, at least among Soviet
tubes. Always the glow was increasing gradually. I have never seen such a
heater flash.
I am wondering if it OK to have such a flash, or should this tube considered
faulty, or is it just a bad tube design, or what?
Regards,
Alex
Re: Heater shining brightly
Alex wrote
,
> After "cool" cathodes of an Electro-Harmonix 12AT7, after
> glowing screen
> grid of a Sovtek EL84 I came across another weird
> phenomenon.
>
> When I power up a Philips Miniwatt 12AX7 (made in
> Australia) the tips of
> its heater filaments, the ends, sticking out from the
> bottom of the cathodes
> and going to the pins 4, 5 and 9, give out a flash of
> bright light, nearly
> like of an incandescent globe.
>
> The flash lasts for about 0.5 seconds. Then the light
> dimms, and eventually
> turns into a "normal" red-orange when the valve warms up.
> Otherwise the tube
> is OK with negligible heater-cathode leakage. Both triodes
> behave exactly
> the same.
>
> The flash occurs on applying heater voltage to a cold
> tube. If the tube has
> alresdy been warmed up, switching heater voltage off and
> then on again does
> not cause the flash.
>
> My explanation is the following. While the heater is cold
> its resistance can
> be as much as 5 times lower the nominal value. On power-up
> the current is
> high. the tips of the heater wire, which are not in the
> [thermal] contact
> with a massive cathode, tend to warm up quicker. Their
> resistance increases
> faster locally, making them dissipate more power per unit
> length, which in
> turn results in more local rise of the resistance, and
> more dissipation. It
> is sort of an avalanche runaway process.
>
> I have never come across such a phenomenon before, at
> least among Soviet
> tubes. Always the glow was increasing gradually. I have
> never seen such a
> heater flash.
>
> I am wondering if it OK to have such a flash, or should
> this tube considered
> faulty, or is it just a bad tube design, or what?
Nice theory, but why don't all valves do the same?
I have some that flash...Mazda ECC81 or 83 I think. I asked
about it once and the consensus was that it's a feature not
a fault. They seem happy enough and test OK.
cheers, Ian
Alex wrote
,
> After "cool" cathodes of an Electro-Harmonix 12AT7, after
> glowing screen
> grid of a Sovtek EL84 I came across another weird
> phenomenon.
>
> When I power up a Philips Miniwatt 12AX7 (made in
> Australia) the tips of
> its heater filaments, the ends, sticking out from the
> bottom of the cathodes
> and going to the pins 4, 5 and 9, give out a flash of
> bright light, nearly
> like of an incandescent globe.
>
> The flash lasts for about 0.5 seconds. Then the light
> dimms, and eventually
> turns into a "normal" red-orange when the valve warms up.
> Otherwise the tube
> is OK with negligible heater-cathode leakage. Both triodes
> behave exactly
> the same.
>
> The flash occurs on applying heater voltage to a cold
> tube. If the tube has
> alresdy been warmed up, switching heater voltage off and
> then on again does
> not cause the flash.
>
> My explanation is the following. While the heater is cold
> its resistance can
> be as much as 5 times lower the nominal value. On power-up
> the current is
> high. the tips of the heater wire, which are not in the
> [thermal] contact
> with a massive cathode, tend to warm up quicker. Their
> resistance increases
> faster locally, making them dissipate more power per unit
> length, which in
> turn results in more local rise of the resistance, and
> more dissipation. It
> is sort of an avalanche runaway process.
>
> I have never come across such a phenomenon before, at
> least among Soviet
> tubes. Always the glow was increasing gradually. I have
> never seen such a
> heater flash.
>
> I am wondering if it OK to have such a flash, or should
> this tube considered
> faulty, or is it just a bad tube design, or what?
Nice theory, but why don't all valves do the same?
I have some that flash...Mazda ECC81 or 83 I think. I asked
about it once and the consensus was that it's a feature not
a fault. They seem happy enough and test OK.
cheers, Ian
Stupid Fat Bastard is Back
"Alexei the Stupid Fat Bastard "
> Hello.
** Fuck off, you fat commie bastard.
> After "cool" cathodes of an Electro-Harmonix 12AT7, after glowing screen
> grid of a Sovtek EL84 I came across another weird phenomenon.
** ROTFLMAO !!
So the demented Commie dim-witted Pig is still at it !!!
> When I power up a Philips Miniwatt 12AX7 (made in Australia) the tips of
> its heater filaments, the ends, sticking out from the bottom of the
> cathodes
> and going to the pins 4, 5 and 9, give out a flash of bright light, nearly
> like of an incandescent globe.
** Yep - a great many of them do just that.
> The flash lasts for about 0.5 seconds. Then the light dimms, and
> eventually
> turns into a "normal" red-orange when the valve warms up. Otherwise the
> tube
> is OK with negligible heater-cathode leakage. Both triodes behave exactly
> the same.
** Errr - yaaawnnn....
> The flash occurs on applying heater voltage to a cold tube. If the tube
> has
> alresdy been warmed up, switching heater voltage off and then on again
> does
> not cause the flash.
** Ditto - seen it heaps of times.
> My explanation is the following. While the heater is cold its resistance
> can
> be as much as 5 times lower the nominal value. On power-up the current is
> high. the tips of the heater wire, which are not in the [thermal] contact
> with a massive cathode, tend to warm up quicker. Their resistance
> increases
> faster locally, making them dissipate more power per unit length, which in
> turn results in more local rise of the resistance, and more dissipation.
> It
> is sort of an avalanche runaway process.
** Plausible theory .....
> I have never come across such a phenomenon before, at least among Soviet
> tubes. Always the glow was increasing gradually. I have never seen such a
> heater flash.
** No surprise- it's completely outlawed in all totalitarian countries.
No * bright flashes * are ever allowed.
Mediocrity is the ONLY thing permitted by law.
Cos Bastards RUN the fucking shit holes !!!!!
> I am wondering if it OK to have such a flash, or should this tube
> considered
> faulty, or is it just a bad tube design, or what?
** The local * Polit Bureau * would fucking shit themselves !!
Un-authorised ** Bright Flashes ** ?????
Tantamount to a Capitalist Pig take over !!!!!!!
Call out the Kremlin Guard !!!
..... Phil
"Alexei the Stupid Fat Bastard "
> Hello.
** Fuck off, you fat commie bastard.
> After "cool" cathodes of an Electro-Harmonix 12AT7, after glowing screen
> grid of a Sovtek EL84 I came across another weird phenomenon.
** ROTFLMAO !!
So the demented Commie dim-witted Pig is still at it !!!
> When I power up a Philips Miniwatt 12AX7 (made in Australia) the tips of
> its heater filaments, the ends, sticking out from the bottom of the
> cathodes
> and going to the pins 4, 5 and 9, give out a flash of bright light, nearly
> like of an incandescent globe.
** Yep - a great many of them do just that.
> The flash lasts for about 0.5 seconds. Then the light dimms, and
> eventually
> turns into a "normal" red-orange when the valve warms up. Otherwise the
> tube
> is OK with negligible heater-cathode leakage. Both triodes behave exactly
> the same.
** Errr - yaaawnnn....
> The flash occurs on applying heater voltage to a cold tube. If the tube
> has
> alresdy been warmed up, switching heater voltage off and then on again
> does
> not cause the flash.
** Ditto - seen it heaps of times.
> My explanation is the following. While the heater is cold its resistance
> can
> be as much as 5 times lower the nominal value. On power-up the current is
> high. the tips of the heater wire, which are not in the [thermal] contact
> with a massive cathode, tend to warm up quicker. Their resistance
> increases
> faster locally, making them dissipate more power per unit length, which in
> turn results in more local rise of the resistance, and more dissipation.
> It
> is sort of an avalanche runaway process.
** Plausible theory .....
> I have never come across such a phenomenon before, at least among Soviet
> tubes. Always the glow was increasing gradually. I have never seen such a
> heater flash.
** No surprise- it's completely outlawed in all totalitarian countries.
No * bright flashes * are ever allowed.
Mediocrity is the ONLY thing permitted by law.
Cos Bastards RUN the fucking shit holes !!!!!
> I am wondering if it OK to have such a flash, or should this tube
> considered
> faulty, or is it just a bad tube design, or what?
** The local * Polit Bureau * would fucking shit themselves !!
Un-authorised ** Bright Flashes ** ?????
Tantamount to a Capitalist Pig take over !!!!!!!
Call out the Kremlin Guard !!!
..... Phil
Re: Heater shining brightly
On Sun, 18 May 2008 10:14:01 GMT, "Alex" <apogosso@bigpond,com > wrote:
>I am wondering if it OK to have such a flash, or should this tube considered
>faulty, or is it just a bad tube design, or what?
Hetaer flash is normal with most Philips small signal tubes because of their
construction.
On Sun, 18 May 2008 10:14:01 GMT, "Alex" <apogosso@bigpond,com > wrote:
>I am wondering if it OK to have such a flash, or should this tube considered
>faulty, or is it just a bad tube design, or what?
Hetaer flash is normal with most Philips small signal tubes because of their
construction.
Re: Heater shining brightly
"François Yves Le Gal" wrote:
>
> On Sun, 18 May 2008 10:14:01 GMT, "Alex" <apogosso@bigpond,com > wrote:
>
> >I am wondering if it OK to have such a flash, or should this tube considered
> >faulty, or is it just a bad tube design, or what?
>
> Hetaer flash is normal with most Philips small signal tubes because of their
> construction.
The flash is caused by the inrush current to the low resistance of the
cold
heater causing a small link designed to rapidly heat and rise in
resistance
before the cold heater warms.
Sort of like having a lamp bulb in series with the heater circuit.
Once the heater gains some heat, its resistance rises, and the
current drops somewhat, and the flash link then drops in temperature
and its resostance falls, allowing more current to the heater
and it rises to its full high resistance as the flash link drops to
a non glowing lower resistance.
The end result is a much shorter time period where a high current
is applied to a tube heater.
If you applied a constant current from cold start to hot condition,
the flash link wouldn't flash.
High inrush current to tube heaters is a nuisance where you have many
tubes.
Patrick Turner.
"François Yves Le Gal" wrote:
>
> On Sun, 18 May 2008 10:14:01 GMT, "Alex" <apogosso@bigpond,com > wrote:
>
> >I am wondering if it OK to have such a flash, or should this tube considered
> >faulty, or is it just a bad tube design, or what?
>
> Hetaer flash is normal with most Philips small signal tubes because of their
> construction.
The flash is caused by the inrush current to the low resistance of the
cold
heater causing a small link designed to rapidly heat and rise in
resistance
before the cold heater warms.
Sort of like having a lamp bulb in series with the heater circuit.
Once the heater gains some heat, its resistance rises, and the
current drops somewhat, and the flash link then drops in temperature
and its resostance falls, allowing more current to the heater
and it rises to its full high resistance as the flash link drops to
a non glowing lower resistance.
The end result is a much shorter time period where a high current
is applied to a tube heater.
If you applied a constant current from cold start to hot condition,
the flash link wouldn't flash.
High inrush current to tube heaters is a nuisance where you have many
tubes.
Patrick Turner.
Re: Stupid Fat Bastard is Back
"Alexei the Stupid Fat Bastard "
> Hello.
** Fuck off, you stupid fat commie bastard.
> After "cool" cathodes of an Electro-Harmonix 12AT7, after glowing screen
> grid of a Sovtek EL84 I came across another weird phenomenon.
** ROTFLMAO !!
So the demented Commie dim-witted Pig is still at it !!!
> When I power up a Philips Miniwatt 12AX7 (made in Australia) the tips of
> its heater filaments, the ends, sticking out from the bottom of the
> cathodes
> and going to the pins 4, 5 and 9, give out a flash of bright light, nearly
> like of an incandescent globe.
** Yep - a great many of them do just that.
> The flash lasts for about 0.5 seconds. Then the light dimms, and
> eventually
> turns into a "normal" red-orange when the valve warms up. Otherwise the
> tube
> is OK with negligible heater-cathode leakage. Both triodes behave exactly
> the same.
** Errr - yaaawwnnnnn .........
> The flash occurs on applying heater voltage to a cold tube. If the tube
> has
> alresdy been warmed up, switching heater voltage off and then on again
> does
> not cause the flash.
** Ditto - seen it heaps of times.
> My explanation is the following. While the heater is cold its resistance
> can
> be as much as 5 times lower the nominal value. On power-up the current is
> high. the tips of the heater wire, which are not in the [thermal] contact
> with a massive cathode, tend to warm up quicker. Their resistance
> increases
> faster locally, making them dissipate more power per unit length, which in
> turn results in more local rise of the resistance, and more dissipation.
> It
> is sort of an avalanche runaway process.
** Plausible theory .....
> I have never come across such a phenomenon before, at least among Soviet
> tubes. Always the glow was increasing gradually. I have never seen such a
> heater flash.
** No surprise- it's completely outlawed in all totalitarian countries.
No * bright flashes * are ever allowed in the USSR !!
Mediocrity is the ONLY thing permitted, by law.
Cos FAT Bastards RUN the fucking shit hole !!!!!
> I am wondering if it OK to have such a flash, or should this tube
> considered
> faulty, or is it just a bad tube design, or what?
** The local * Polit Bureau * would fucking shit themselves !!
Un-authorised ** Bright Flashes ** ?????????????
Tantamount to a * Capitalist Pig * take over !!!!!!!
Call out the Kremlin Guard !!!
The fucking Yankees are coming ......
..... Phil
"Alexei the Stupid Fat Bastard "
> Hello.
** Fuck off, you stupid fat commie bastard.
> After "cool" cathodes of an Electro-Harmonix 12AT7, after glowing screen
> grid of a Sovtek EL84 I came across another weird phenomenon.
** ROTFLMAO !!
So the demented Commie dim-witted Pig is still at it !!!
> When I power up a Philips Miniwatt 12AX7 (made in Australia) the tips of
> its heater filaments, the ends, sticking out from the bottom of the
> cathodes
> and going to the pins 4, 5 and 9, give out a flash of bright light, nearly
> like of an incandescent globe.
** Yep - a great many of them do just that.
> The flash lasts for about 0.5 seconds. Then the light dimms, and
> eventually
> turns into a "normal" red-orange when the valve warms up. Otherwise the
> tube
> is OK with negligible heater-cathode leakage. Both triodes behave exactly
> the same.
** Errr - yaaawwnnnnn .........
> The flash occurs on applying heater voltage to a cold tube. If the tube
> has
> alresdy been warmed up, switching heater voltage off and then on again
> does
> not cause the flash.
** Ditto - seen it heaps of times.
> My explanation is the following. While the heater is cold its resistance
> can
> be as much as 5 times lower the nominal value. On power-up the current is
> high. the tips of the heater wire, which are not in the [thermal] contact
> with a massive cathode, tend to warm up quicker. Their resistance
> increases
> faster locally, making them dissipate more power per unit length, which in
> turn results in more local rise of the resistance, and more dissipation.
> It
> is sort of an avalanche runaway process.
** Plausible theory .....
> I have never come across such a phenomenon before, at least among Soviet
> tubes. Always the glow was increasing gradually. I have never seen such a
> heater flash.
** No surprise- it's completely outlawed in all totalitarian countries.
No * bright flashes * are ever allowed in the USSR !!
Mediocrity is the ONLY thing permitted, by law.
Cos FAT Bastards RUN the fucking shit hole !!!!!
> I am wondering if it OK to have such a flash, or should this tube
> considered
> faulty, or is it just a bad tube design, or what?
** The local * Polit Bureau * would fucking shit themselves !!
Un-authorised ** Bright Flashes ** ?????????????
Tantamount to a * Capitalist Pig * take over !!!!!!!
Call out the Kremlin Guard !!!
The fucking Yankees are coming ......
..... Phil
Alexei the Fat Commie Bastard
"Alexei the Fat Commie Bastard "
> Thanks. Do you know what is special, and for what purpose such has been
> done?
** Yeah - it's done to deliberately to annoy
all Stupid Fat Bastards like YOU !!!
... Phil
"Alexei the Fat Commie Bastard "
> Thanks. Do you know what is special, and for what purpose such has been
> done?
** Yeah - it's done to deliberately to annoy
all Stupid Fat Bastards like YOU !!!
... Phil
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