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#1
Posted to rec.audio.tubes
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At power on tube filaments light up more than normal for a sec
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 |
#2
Posted to rec.audio.tubes
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At power on tube filaments light up more than normal for a sec
"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 |
#3
Posted to rec.audio.tubes
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At power on tube filaments light up more than normal for a sec
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. |
#4
Posted to rec.audio.tubes
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At power on tube filaments light up more than normal for a sec
"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 |
#5
Posted to rec.audio.tubes
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At power on tube filaments light up more than normal for a sec
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. |
#6
Posted to rec.audio.tubes
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At power on tube filaments light up more than normal for a sec
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 |
#7
Posted to rec.audio.tubes
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At power on tube filaments light up more than normal for a sec
"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 |
#8
Posted to rec.audio.tubes
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At power on tube filaments light up more than normal for a sec
"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 |
#9
Posted to rec.audio.tubes
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At power on tube filaments light up more than normal for a sec
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. |
#10
Posted to rec.audio.tubes
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At power on tube filaments light up more than normal for a sec
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 |
#11
Posted to rec.audio.tubes
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At power on tube filaments light up more than normal for a sec
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 |
#12
Posted to rec.audio.tubes
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At power on tube filaments light up more than normal for a sec
"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. |
#13
Posted to rec.audio.tubes
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At power on tube filaments light up more than normal for a sec
"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 |
#14
Posted to rec.audio.tubes
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At power on tube filaments light up more than normal for a sec
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 |
#15
Posted to rec.audio.tubes
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At power on tube filaments light up more than normal for a sec
"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. |
#16
Posted to rec.audio.tubes
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At power on tube filaments light up more than normal for a sec
"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 |
#17
Posted to rec.audio.tubes
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At power on tube filaments light up more than normal for a sec
"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 |
#18
Posted to rec.audio.tubes
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At power on tube filaments light up more than normal for a sec
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 |
#19
Posted to rec.audio.tubes
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At power on tube filaments light up more than normal for a sec
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 |
#20
Posted to rec.audio.tubes
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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 |
#21
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At power on tube filaments light up more than normal for a sec
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 |
#22
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At power on tube filaments light up more than normal for a sec
Flashing heaters, another reason to go solid state.
Jan |
#23
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At power on tube filaments light up more than normal for a sec
flipper wrote:
On Mon, 08 Dec 2008 16:27:12 +0000, Ian Bell 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 |
#24
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At power on tube filaments light up more than normal for a sec
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 |
#25
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At power on tube filaments light up more than normal for a sec
"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 |
#26
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At power on tube filaments light up more than normal for a sec
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. |
#27
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At power on tube filaments light up more than normal for a sec
"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 |
#28
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At power on tube filaments light up more than normal for a sec
"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 |
#29
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At power on tube filaments light up more than normal for a sec
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. |
#30
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At power on tube filaments light up more than normal for a sec
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. |
#31
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At power on tube filaments light up more than normal for a sec
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. |
#32
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At power on tube filaments light up more than normal for a sec
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. |
#33
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At power on tube filaments light up more than normal for a sec
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 |
#34
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At power on tube filaments light up more than normal for a sec
"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. |
#35
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At power on tube filaments light up more than normal for a sec
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 |
#36
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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. 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 |
#37
Posted to rec.audio.tubes
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At power on tube filaments light up more than normal for a sec
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 |
#38
Posted to rec.audio.tubes
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At power on tube filaments light up more than normal for a sec
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. |
#39
Posted to rec.audio.tubes
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At power on tube filaments light up more than normal for a sec
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 |
#40
Posted to rec.audio.tubes
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At power on tube filaments light up more than normal for a sec
"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 |
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