fish@gemed.com (Mark Fisher) (11/29/90)
I think I can answer my own question. I went to the hardware store and looked at some quartz-halogen replacement bulbs. They have what appears to be a tungsten filament wire inside a quartz tube. Going off the deep end, I would say that the resistance of the wire would limit the current and no ballast is needed. I would also assume that the dimmer circuit in halogen lamps is a regular high wattage dimmer. I noticed on the demo lamp that dimming the light made the quartz-halogen tube humm loud enough that I could hear it in a noisy wharehouse type of store. I looked up halogen in my dictionary. It said it was one of the very active chemical elements, fluorine, chlorine, bromine, astatine, or iodine. How does this apply to a light bulb? -- // Mark M. Fisher // fish@gemed.ge.com // uunet!crdgw1!gemed!fish // sun!sunbrew!gemed!fish
rando@skipper.dfrf.nasa.gov (Randy Brumbaugh) (11/29/90)
Someone asked what the halogen gas did for these lamps. Hope this helps . . . (In this posting, "lamp" means light bulb, not a lighting fixture). A "halogen" lamp (also sometimes called a "quartz", "tunsten- halogen", or a "Quartz-iodide" lamp) is basically the same as a regular incandescent lamp -- it produces light by heating a tungsten filament in a sealed envelope containing some gas. It is still a form of incandescent lighting. No ballast is needed for halogen lamps, although some small fixtures use lower voltage lamps and need a step-down transformer. The difference is in the envelope, which is made of quartz to handle the high temperature operation needed; and in the gas which fills the envelope. The gas is a member of the halogen family. Regular incandescent lamps use an inert gas. In a regular incandescent lamp, the tungsten "boils" off the filament during operation. It eventually contacts the cooler glass envelope, where it deposits itself. This results in darkening of the envelope as the lamp ages, and in weakening of the filament. A chemical process (the halogen cycle) is used to improve this in these new fangled "halogen" lamps. The tungsten chemically bonds with the halogen gas in the envelope. When the gas contacts the hot filament, the chemical bond is broken, and the tungsten is re-deposited in the filament. These lamps won't last forever, because the tungsten isn't deposited at the same spot it came off the filament. This gives lamp designers 2 options: - make the lamp produce brighter, higher color temperature light at the same life expectancy. -OR- - make the lamp the same brightness with a longer life. To maintain the halogen cycle, the lamp must run at fairly high temperatures and pressures. Dimming may reduce this somewhat, and cause the envelope to darken, but operating a while at full brightness will reverse the process. Also, the quartz envelope shouldn't be touched by bare hands -- oils on the skin will weaken the structure and may cause bubbles or lamp failure. Tungsten-halogen (T-H) lamps are now used almost exclusively for stage and television lighting applicatuions, where they have been around for quite a while. This is due to thier longer life/higher color temp and the fact that light output does not decrease as the lamp ages, as it does with regular incandescent lights. Randy Brumbaugh rando@skipper.dfrf.nasa.gov
bhoughto@cmdnfs.intel.com (Blair P. Houghton) (11/29/90)
In article <714@skipper.dfrf.nasa.gov> rando@skipper.dfrf.nasa.gov (Randy Brumbaugh) writes: >A chemical process (the halogen cycle) is used to improve this >in these new fangled "halogen" lamps. The tungsten chemically >bonds with the halogen gas in the envelope. When the gas >contacts the hot filament, the chemical bond is broken, and >the tungsten is re-deposited in the filament. These lamps >won't last forever, because the tungsten isn't deposited >at the same spot it came off the filament. If a region starts to thin-out its resistivity increases, increasing its power dissipation, increasing its heat. The rate of deposition is a monotonic function of the temperature, so the hotter spots tend to _collect_ tungsten, fattening them. The halogen cycle not only prevents rapid loss of filament material, it repairs minor flaws in the filament and prevents hot-spots due to these flaws. Halogen lamps burn out (barring some extensive flaw) only when one of the non-tungsten parts fails (the filament supports weaken from temperature cycling, the way the filament would if it weren't for the halogen cycle). >Also, the quartz envelope shouldn't be touched by bare >hands -- oils on the skin will weaken the structure and may >cause bubbles or lamp failure. The oil causes a region of different thermal conductivity; when the heat is applied this will cause a region of different temperature which will cause a difference in expansion which will cause a stress that will rupture the envelope. The oil doesn't "weaken the structure." You can wipe it off. >Tungsten-halogen (T-H) lamps are now used almost exclusively >for stage and television lighting applicatuions, where they --Blair "Stage Nerds 'R' Us..."
bhoughto@cmdnfs.intel.com (Blair P. Houghton) (11/30/90)
In article <1147@inews.intel.com> bhoughto@cmdnfs.intel.com (Blair P. Houghton) writes: >If a region starts to thin-out its resistivity increases, Bubblehead. That's "resistance," not "resistivity." It's the cross-sectional area that's changing, not the mean free path... --Blair "What a maroon."
bobt@pogo.WV.TEK.COM (Bob Tidrick) (11/30/90)
>>in these new fangled "halogen" lamps. The tungsten chemically New fangled they are not. The have been around quite a while. >>contacts the hot filament, the chemical bond is broken, and >>the tungsten is re-deposited in the filament. These lamps >>won't last forever, because the tungsten isn't deposited >>at the same spot it came off the filament. One thing that has bothered me about these Halogen lamps with the dimmer is, from my experiance if the bulb is not kept at least at a certian high temperature they will fail faster. I have seen halogen bulbs grow tungsten crystals on the ends of the filament when run at a lower then rated voltage. Apparently this is because when the filament is at a lower temperature the tungsten is not redeposited on the filament while the bulb is operating. When it is turned off and the gas cools it is deposited at the coolest point. In this case the ends of the filament. The crystals grow depleating the material on the rest of the filament. Hot spots do occur but there is always some tungsten trapped in the gas when the bulb is turned off it cools and again is deposited on the crystals. The bulbs we used where rated at about 5000 Hrs. Most of them lasted about 2000. Some lasted as little as 500 Hrs. These were bulbs rated at 12 Volts being run at 10V. I wonder if the manufactures of these lamps know about this? -- Bob Tidrick GPID Engineering Tektronix Inc. Wilsonville OR.
schuster@cup.portal.com (Michael Alan Schuster) (11/30/90)
>The halogen cycle not only prevents rapid loss of filament >material, it repairs minor flaws in the filament and prevents >hot-spots due to these flaws. > >Halogen lamps burn out (barring some extensive flaw) only >when one of the non-tungsten parts fails (the filament supports >weaken from temperature cycling, the way the filament would >if it weren't for the halogen cycle). What's the principle behind the "krypton" flashlight bulbs being sold now, and market as "70% brighter" than the standard type?
whit@milton.u.washington.edu (John Whitmore) (11/30/90)
In article <36350@cup.portal.com> schuster@cup.portal.com (Michael Alan Schuste\ > >What's the principle behind the "krypton" flashlight bulbs being sold >now, and market as "70% brighter" than the standard type? There are three major different types of incandescant bulbs. Vacuum, inert gas, and halogen. Vacuum bulbs are more energy-efficient, and have a lifetime of circa 5-10 hours. Inert gas bulbs have some gas-cooling of hot spots, so last longer (circa 750 hours), but still blacken as they age. Halogen bulbs do not blacken, but must be run hot. Traditional flashlight bulbs have been vacuum types. For larger power outputs (which modern batteries make feasible), one can use a very dense gas (Krypton) which has lower thermal conductivity than Nitrogen (which is the fill gas in most 100W household lamps). The '70% brighter' effect is due to the filament running hotter (and taking 50% more power). I tested bulbs of all three types for my bicycle light; the vacuum bulb spectrum was dreadfully red. The halogen and the Krypton had the same color temperature, with the Krypton being slightly higher power output. I ended up using the halogen (and have had a hundred or so hours use so far) but the Krypton bulb is what I'll be replacing it with (the cost is circa 8:1 in favor of Krypton). John Whitmore
sg1q+@andrew.cmu.edu (Simon Peter Gatrall) (11/30/90)
I didn't see the original question, but I'll answer this anyway. Yes and no. Some halogen lamps are 12V (others are 6V or 24V or 120V) so they need a power supply. Some manufacturers call this a ballast even though it is not a ballast in the sense of a florescent light ballast. Higher wattage halogen lamps are usually 120V ac. There are solid state power supplies rated for use with 12V halogen lamps available. -Simon Gatrall sg1q+@andrew.cmu.edu
phil@brahms.amd.com (Phil Ngai) (12/01/90)
In article <10147@pogo.WV.TEK.COM> bobt@pogo.WV.TEK.COM (Bob Tidrick) writes: |The bulbs we used where rated |at about 5000 Hrs. Most of them lasted about 2000. Some lasted as little |as 500 Hrs. These were bulbs rated at 12 Volts being run at 10V. Is there any way you can avoid running them below their rated voltage? Why are you doing this instead of getting bulbs rated at less wattage? What do you think the manufacturers could do about their products being used at a temperature too low for the full halogen cycle to operate? -- Compost: it's the right thing to do.
commgrp@silver.ucs.indiana.edu (BACS Data Communications Group) (12/01/90)
Halogen lamps do not need ballasts, however, large halogen lamps and arrays of lamps are sometimes connected in series with low-inductance, high-current, air-core "inrush chokes" to protect switch contacts: Resistance of metal increases with temperature; there is significant difference between tungsten's cold resistance and its resistance at halogen-lamp operating temperature. -- Frank Reid reid@ucs.indiana.edu
abar@cbnewsk.att.com (jerome.t.abar..jr) (12/01/90)
In article <1990Nov30.174758.979@amd.com>, phil@brahms.amd.com (Phil Ngai) writes: > In article <10147@pogo.WV.TEK.COM> bobt@pogo.WV.TEK.COM (Bob Tidrick) writes: > |The bulbs we used where rated > |at about 5000 Hrs. Most of them lasted about 2000. Some lasted as little > |as 500 Hrs. These were bulbs rated at 12 Volts being run at 10V. > > Is there any way you can avoid running them below their rated > voltage? Why are you doing this instead of getting bulbs rated > at less wattage? What do you think the manufacturers could do > about their products being used at a temperature too low for > the full halogen cycle to operate? Would the halogen lamps last longer if you left them on continuously as opposed to turning them on and off, cooling and heating them (a previous poster mentioned crystals growing in cool spots) Thanks. -- ******************************************************************************* ** Tom Abar My Company's Nifty, My Company's Fine, ** ** mvjta@mvgpn.att.com But These Opinions Are Strictly MINE!! ** *******************************************************************************
karn@envy.bellcore.com (Phil R. Karn) (12/01/90)
In article <1147@inews.intel.com>, bhoughto@cmdnfs.intel.com (Blair P. Houghton) writes: |> >Also, the quartz envelope shouldn't be touched by bare |> >hands -- oils on the skin will weaken the structure and may |> >cause bubbles or lamp failure. |> |> The oil causes a region of different thermal conductivity; |> when the heat is applied this will cause a region of |> different temperature which will cause a difference in |> expansion which will cause a stress that will rupture the |> envelope. The oil doesn't "weaken the structure." You can |> wipe it off. I don't think that's quite right. Quartz is used precisely because of its very low temperature expansion coefficient. I think the problem is that the heat will decompose the oil, producing elemental carbon which will then absorb the light hitting it from the filament. This causes a hot spot on the surface of the envelope which could well cause it to soften and fail. Phil
bhoughto@cmdnfs.intel.com (Blair P. Houghton) (12/02/90)
In article <1990Dec1.032426@envy.bellcore.com> karn@thumper.bellcore.com writes: >In article <1147@inews.intel.com>, bhoughto@cmdnfs.intel.com (Blair P. >Houghton) writes: [...deformation ==> rupture...] >|> The oil doesn't "weaken the structure." You can >|> wipe it off. > >I don't think that's quite right. Quartz is used precisely >because of its very low temperature expansion coefficient. Very low != nonexistant. Also, quartz is very brittle. Any deformation causes catastrophic displacement (cleaving). When there's a uniformity of heat distribution, things expand normally. When there isn't, they don't. >I think the problem is that the heat will decompose the oil, producing >elemental carbon which will then absorb the light hitting it from the >filament. This causes a hot spot on the surface of the envelope which >could well cause it to soften and fail. Take a halogen lamp. Turn it on. Allow a drop of water to fall on it. Run like hell. You don't need any chemistry. Temperature differences are all you need to cause one of these to blow. I don't think you can "soften" quartz without _extreme_ temperatures (thousands and thousands of K). --Blair "Billions and billions of Big Macs..."
bhoughto@cmdnfs.intel.com (Blair P. Houghton) (12/02/90)
In article <1990Nov30.174758.979@amd.com> phil@brahms.amd.com (Phil Ngai) writes: >at less wattage? What do you think the manufacturers could do >about their products being used at a temperature too low for >the full halogen cycle to operate? Sell more of them as replacements... --Blair "It's pretty obvious, really."
metzger@cup.portal.com (David G Metzger) (12/02/90)
In article <1197@inews.intel.com>, bhoughto@cmdnfs.intel.com (Blair P. Houghton) writes: >In article <1990Dec1.032426@envy.bellcore.com> karn@thumper.bellcore.com write s >: >>In article <1147@inews.intel.com>, bhoughto@cmdnfs.intel.com (Blair P. >>Houghton) writes: >[...deformation ==> rupture...] >>|> The oil doesn't "weaken the structure." You can >>|> wipe it off. >> >>I don't think that's quite right. Quartz is used precisely >>because of its very low temperature expansion coefficient. > >Very low != nonexistant. Also, quartz is very brittle. >Any deformation causes catastrophic displacement >(cleaving). When there's a uniformity of heat ^^^^^^^^ >distribution, things expand normally. When there isn't, >they don't. Quartz does not have cleavage planes. When quartz breaks, it is by conchoidal fracture. David Metzger metzger@cup.portal.com sun!portal!cup.portal.com!metzger
kilian@cray.com (Alan Kilian) (12/03/90)
In article <1197@inews.intel.com>, bhoughto@cmdnfs.intel.com (Blair P. Houghton) writes: > In article <1990Dec1.032426@envy.bellcore.com> karn@thumper.bellcore.com writes: > >In article <1147@inews.intel.com>, bhoughto@cmdnfs.intel.com (Blair P. > >Houghton) writes: > [...deformation ==> rupture...] > >|> The oil doesn't "weaken the structure." You can > >|> wipe it off. > > > >I don't think that's quite right. Quartz is used precisely > >because of its very low temperature expansion coefficient. > > Very low != nonexistant. Also, quartz is very brittle. > Any deformation causes catastrophic displacement > (cleaving). When there's a uniformity of heat > distribution, things expand normally. When there isn't, > they don't. > > >I think the problem is that the heat will decompose the oil, producing > >elemental carbon which will then absorb the light hitting it from the > >filament. This causes a hot spot on the surface of the envelope which > >could well cause it to soften and fail. > > Take a halogen lamp. Turn it on. Allow a drop of water to > fall on it. Run like hell. > > You don't need any chemistry. Temperature differences > are all you need to cause one of these to blow. > > I don't think you can "soften" quartz without _extreme_ > temperatures (thousands and thousands of K). > > --Blair > "Billions and billions of Big Macs..." From the CRC handbook od chemistry and physics 63 edition 1982-1983 PP F65: Coefficient of thermal expansion 5.5 X 10^-7 cm/cm/degree C From 20 to 320 C (That's way low) Tensile strength 7,000 PSI Compressive strength > 160,000 PSI (That's very strong) Softening point (Approx) 1665 Degrees C (1938 degrees K) (That's way up there) So, If I place some oil on the quartz with the lamp off and let the temperatures equalize and then turn on the lamp WHY does the quartz break (If it really does as so many have said). I guess I'll have to buy some bulbs and try this at home because I don't buy any of these theorys. (Except the carbon one maybe) -Alan Kilian Cray Research, Inc. 655 F Lone Oak Drive Eagan, MN 55121 kilian@cray.com
bhoughto@cmdnfs.intel.com (Blair P. Houghton) (12/03/90)
In article <153447.28605@timbuk.cray.com> kilian@cray.com (Alan Kilian) writes: > >Coefficient of thermal expansion 5.5 X 10^-7 cm/cm/degree C From 20 to 320 C > (That's way low) Not low enough. >Tensile strength 7,000 PSI Compressive strength > 160,000 PSI > (That's very strong) Not strong enough. >Softening point (Approx) 1665 Degrees C (1938 degrees K) > (That's way up there) Lower than I thought, but higher than any spot of carbonization will stick around to reach. >So, If I place some oil on the quartz with the lamp off and let the >temperatures equalize and then turn on the lamp WHY does the quartz >break (If it really does as so many have said). Halogen lamps in these pole-lamp assemblies come with expensive-looking protective gear to keep the shards of quartz envelope from splattering all over your living room. They break. The skin oil keeps heat in the quartz that is escaping elsewhere on the envelope. The temperature difference causes localized stresses. Poof. --Blair "Poof."
tell@oscar.cs.unc.edu (Stephen Tell) (12/03/90)
In article <153447.28605@timbuk.cray.com> kilian@cray.com (Alan Kilian) writes: >In article <1197@inews.intel.com>, bhoughto@cmdnfs.intel.com (Blair P. Houghton) writes: >> In article <1990Dec1.032426@envy.bellcore.com> karn@thumper.bellcore.com writes: >> >In article <1147@inews.intel.com>, bhoughto@cmdnfs.intel.com (Blair P. >> >Houghton) writes: >> [...deformation ==> rupture...] >> >|> The oil doesn't "weaken the structure." You can >> >|> wipe it off. You can certainly clean the oil off before turning the lamp on and get near-normal bulb life. Instructions packed with lamps I've seen say to clean them with alcohol if you accidently touch them during installation. I've done this with no problems. >> >I think the problem is that the heat will decompose the oil, producing >> >elemental carbon which will then absorb the light hitting it from the >> >filament. This causes a hot spot on the surface of the envelope which >> >could well cause it to soften and fail. >> I don't think you can "soften" quartz without _extreme_ >> temperatures (thousands and thousands of K). I have personaly replaced a 750 Watt (or maybe it was 1KW) quartz/halogen lamp that had a big blackened "tumor" of glass on the side where the envelope had deformed. I was told that this happened because someone got a fingerprint on the bulb when installing it. If this is not correct, what caused this? BTW, this lamp was not the long thin kind found in $10 backyard lights, but one with a two-pin base and the filament coiled into about a 1" x 1/4" dia spiral. (Type FEL for 1K or the equivilent in 750). Sometimes the envelope has broken; we attributed this to rough handling fo the stage fixture, but it could be the "different thermal expansion --> breakage" mechanism. >I guess I'll have to buy some bulbs and try this at home because I don't >buy any of these theorys. (Except the carbon one maybe) I've noticed some computer-surplus places advertising 1KW quarts lamps for very reasonable prices... >[Alan Kilian Cray Research, Inc. kilian@cray.com]
adamd@rhi.hi.is (Adam David) (12/03/90)
In <36440@cup.portal.com> metzger@cup.portal.com (David G Metzger) writes: >In article <1197@inews.intel.com>, bhoughto@cmdnfs.intel.com > (Blair P. Houghton) writes: >>Very low != nonexistant. Also, quartz is very brittle. >>Any deformation causes catastrophic displacement >>(cleaving). When there's a uniformity of heat > ^^^^^^^^ >>distribution, things expand normally. When there isn't, >>they don't. > Quartz does not have cleavage planes. When quartz breaks, it >is by conchoidal fracture. Depends on how it grew doesn't it? Defects in the crystal can form very regular fracture planes that behave just like cleavage planes. This weak area is the one most likely to break if the deformation occurs nearby. But then again, there aren't supposed to be any defects are there? Adam David. adamd@rhi.hi.is
chuck@marie.mit.edu (PARSONS, CHARLES) (12/04/90)
In article <2473@krafla.rhi.hi.is>, adamd@rhi.hi.is (Adam David) writes... >In <36440@cup.portal.com> metzger@cup.portal.com (David G Metzger) writes: > >>In article <1197@inews.intel.com>, bhoughto@cmdnfs.intel.com >> (Blair P. Houghton) writes: >>>(cleaving). When there's a uniformity of heat >> ^^^^^^^^ > >> Quartz does not have cleavage planes. When quartz breaks, it >>is by conchoidal fracture. > >Depends on how it grew doesn't it? Defects in the crystal can form very regular >fracture planes that behave just like cleavage planes. This weak area is the one >most likely to break if the deformation occurs nearby. But then again, there >aren't supposed to be any defects are there? > "Quartz" halogen light tubes are not Crystals they are amorphous. The quartz label just refers to the fact that the glass is almost pure SiO2 without the usual salts added to window glass to lower the melting point. Chuck@mitlns.mit.edu
rsnider@xrtll.uucp (Richard Snider) (12/04/90)
In article <FISH.90Nov28100429@his.gemed.com> fish@gemed.ge.com (Mark Fisher, GE Medical, Milwaukee WI, x4-6553) writes: >I think I can answer my own question. I went to the hardware store >and looked at some quartz-halogen replacement bulbs. They have what >appears to be a tungsten filament wire inside a quartz tube. Going >off the deep end, I would say that the resistance of the wire would >limit the current and no ballast is needed. A quartz-halogen bulb is no different from a regualar incandescent in as much as how the power should be supplied to it. Most of the "Indoor" type of fixtures use bulbs that run at 12V (For many reasons). This is why in some fixtures there is a step-down transformer. It is not being used for current limiting or starting as it would be in a flourescent. Many "Outdoor" Halogens tend to use the line voltage directly. >I looked up halogen in my dictionary. It said it was one of the very >active chemical elements, fluorine, chlorine, bromine, astatine, or >iodine. How does this apply to a light bulb? When the bulb is run in the correct temperature range, the halogen causes re-depositing of the tungsten that is boiled off the filament at the elevated temperature. At lower temperatures (ie. light is dimmed with a dimmer) the boiling of tungsten from the filament is not a large effect so the scrubbing and re-deposition of the tungsten is not so important. Lastly, I am suspicious in general of many of the "indoor" halogen types of lights. To get maximum "light for the buck" a halogen bulb must be run a LOT hotter than the ones I see in stores are. Specifically I have done quite a bit of theater lighting using lots of halogen equipment, and usually when a light is on full, in order to get proper re-deposition the quartz tube will glow bright red. It will also keep glowing for several SECONDS after the light is shut down. This is the temperature they must be run at to make the halogen inside be reasonably useful. Otherwise you may as well have regular light bulbs. As far as getting oil on the bulbs (from skin or other things), if the bulb is run in the correct temperature range (HOT) then getting any kind of oil on the bulb will usually result in premature failure due to a carbon hot spot, followed by deformation, followed by (often spectacular) destruction. If anyone out there dosn't believe that the quartz tube can deform, I have a few "neat looking" bulbs that show quite nicely how well the quartz tube can deform. ...Rich ------------------------------------------------------------------------ Where: ..uunet!mnetor!yunexus!xrtll!rsnider Also: rsnider@xrtll.UUCP An unbreakable tool is useful for breaking other tools.
vail@tegra.COM (Johnathan Vail) (12/04/90)
In article <75525@iuvax.cs.indiana.edu> commgrp@silver.ucs.indiana.edu (BACS Data Communications Group) writes: Halogen lamps do not need ballasts, however, large halogen lamps and arrays of lamps are sometimes connected in series with low-inductance, high-current, air-core "inrush chokes" to protect switch contacts: Resistance of metal increases with temperature; there is significant difference between tungsten's cold resistance and its resistance at halogen-lamp operating temperature. I posted a question about some halogen trak-lights. I have found a few more things out (like the bulbs still work). To re-cap my earlier post and pose the question differently: * I bought a set of trak lights and some 110v halogen bulbs * the bulbs didn't work in the fixture so I tested the bulbs with a meter and they read open. it was easier than trying another fixture. I assumed something killed them * The bulbs are now known good and the original problem is solved (the fixture contact needed adjusting) MY QUESTION: Why does the bulb read open on a 20 meg scale? Theory: the rectifier circuit is causing this? jv ``There's nothing remarkable about it. All one has to do is hit the right keys at the right time and the instrument plays itself.'' -- J. S. Bach _____ | | Johnathan Vail | n1dxg@tegra.com |Tegra| (508) 663-7435 | N1DXG@448.625-(WorldNet) ----- jv@n1dxg.ampr.org {...sun!sunne ..uunet}!tegra!vail
rambler@pnet51.orb.mn.org (Dan Meyer) (12/05/90)
kilian@cray.com (Alan Kilian) writes: >In article <1197@inews.intel.com>, bhoughto@cmdnfs.intel.com (Blair P. Houghton) writes: >> Take a halogen lamp. Turn it on. Allow a drop of water to >> fall on it. Run like hell. >> >> You don't need any chemistry. Temperature differences >> are all you need to cause one of these to blow. Take *any* incandesnant lamp. turn it on. Allow a drop of water to fall on it. run like hell. Most incandesant lamps break under these conditions! >> >> I don't think you can "soften" quartz without _extreme_ >> temperatures (thousands and thousands of K). Agreed. isn't quartz a mineral? quite a bit different than glass? >> >> --Blair >> "Billions and billions of Big Macs..." -- Dan Meyer Remember: " Buffalo never Oink " Seen on a South Dakota travel brocure. Advertisment: Try the Railway Post Office , a railfan BBS ! (612) 377-2197. UUCP: {crash tcnet}!orbit!pnet51!rambler ARPA: crash!orbit!pnet51!rambler@nosc.mil INET: rambler@pnet51.orb.mn.org
henry@zoo.toronto.edu (Henry Spencer) (12/06/90)
In article <3561@orbit.cts.com> rambler@pnet51.orb.mn.org (Dan Meyer) writes: >Agreed. isn't quartz a mineral? quite a bit different than glass? Not all that different. Quartz is crystals of silica (SiO2). Most glass is non-crystalline impure silica. The impurities are there to change its properties in various ways, most notably to reduce its softening point. Pure-silica glass does exist; the only difference between it and quartz is that the molecular structure of the glass is quasi-random while the structure of the quartz is a regular array of atoms. (One of the problems with working pure-silica glass, in fact, is that it has a tendency to try to crystallize into quartz.) I believe the bulbs actually use the glass, not true crystalline quartz. -- "The average pointer, statistically, |Henry Spencer at U of Toronto Zoology points somewhere in X." -Hugh Redelmeier| henry@zoo.toronto.edu utzoo!henry
rrw@naucse.cse.nau.edu (Robert Wier) (12/10/90)
All of this talk about Halogen lights and possible destruction
thereof make me wonder if similar technology is being applied
to transmitting tubes (and maybe CRTs?). I know from talking
to broadcast engineers that you only have a matter of seconds
to shut off a 25,000 watt transmitting tube if the cooling
fans fail. In fact we have a very nice EMAC tube upstairs in
the electronics lab (4CX5000 I believe) that got destructed just
this way. The cooling fins (made of some type of metal) are
MELTED.
The tungston re-deposition properties of halogen lamps would seem
a natural for life extension on transmitting tubes (IF that is
a desired property - maybe not for the manufacturers :-) )
or would the presence of grids, plates, and other elements
negate the use of halogen?
- Bob Wier
-------------- insert favorite standard disclaimers here ----------
College of Engineering
Northern Arizona University / Flagstaff, Arizona
Internet: rrw@naucse.cse.nau.edu | BITNET: WIER@NAUVAX | WB5KXH
or uucp: ...arizona!naucse!rrwjgo@mcgp1.UUCP (John Opalko, N7KBT) (12/11/90)
In article <3026@naucse.cse.nau.edu> rrw@naucse.cse.nau.edu (Robert Wier) writes:
->
-> The tungston re-deposition properties of halogen lamps would seem
-> a natural for life extension on transmitting tubes (IF that is
-> a desired property - maybe not for the manufacturers :-) )
-> or would the presence of grids, plates, and other elements
-> negate the use of halogen?
Kind of contrary to the definition of a VACUUM tube, though, isn't it?rrw@naucse.cse.nau.edu (Robert Wier) (12/12/90)
In article <4676@mcgp1.UUCP>, jgo@mcgp1.UUCP (John Opalko, N7KBT) writes: > In article <3026@naucse.cse.nau.edu> rrw@naucse.cse.nau.edu (Robert Wier) writes: > -> > -> The tungston re-deposition properties of halogen lamps would seem > -> a natural for life extension on transmitting tubes (IF that is > -> a desired property - maybe not for the manufacturers :-) ) > -> or would the presence of grids, plates, and other elements > -> negate the use of halogen? > > Kind of contrary to the definition of a VACUUM tube, though, isn't it? Aha! VERY good point. My brain is scrambled from thinking about silicon for too long (sigh...). I once had a QSL card which had a cartoon about some guys using plumbing tools to try to stop "grid leaks". If you remember this, you're as old as I am!!! - Bob Wier -------------- insert favorite standard disclaimers here ---------- College of Engineering Northern Arizona University / Flagstaff, Arizona Internet: rrw@naucse.cse.nau.edu | BITNET: WIER@NAUVAX | WB5KXH or uucp: ...arizona!naucse!rrw