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Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems. |
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mercury lights
Could someone tell me what might be the cause of a mercury vapor light to
intermittantly go off and in a few minutes come back on? It doesn't do it consistantly, but rather often. Thanks, -- curt |
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"hungry1" writes:
Could someone tell me what might be the cause of a mercury vapor light to intermittantly go off and in a few minutes come back on? It doesn't do it consistantly, but rather often. 1. Bad lamp. 2. Bad ballast. 3. Bad wiring. 4. If solar activated, photodetector being fooled by stray light or someone messing with it using a flashlight or laser pointer. --- sam | Sci.Electronics.Repair FAQ Mirror: http://repairfaq.ece.drexel.edu/ Repair | Main Table of Contents: http://repairfaq.ece.drexel.edu/REPAIR/ +Lasers | Sam's Laser FAQ: http://repairfaq.ece.drexel.edu/sam/lasersam.htm | Mirror Sites: http://repairfaq.ece.drexel.edu/REPAIR/F_mirror.html Note: These links are hopefully temporary until we can sort out the excessive traffic on Repairfaq.org. Important: Anything sent to the email address in the message header above is ignored unless my full name is included in the subject line. Or, you can contact me via the Feedback Form in the FAQs. |
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"hungry1" wrote in message news:1103993274.1ab3a0becb9f018c0d9c4d5e6a1108d6@t eranews... | Could someone tell me what might be the cause of a mercury vapor light to | intermittantly go off and in a few minutes come back on? It doesn't do it | consistantly, but rather often. | Thanks, End of life for the lamp. N |
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Could someone tell me what might be the cause of a mercury vapor light to
intermittantly go off and in a few minutes come back on? Curt- To add to Sam Goldwasser's comments, it is possible that a very short glitch in the AC power, is causing the light to go out. Once it is out, it has to warm up before it comes back on. I think a good lamp would have the ability to withstand a short outage without having to heat-up again. Perhaps this is due to a defective lamp or one that is getting old. Has it always done this, or just started after several years of service? If it has always done it, could you have the wrong wattage lamp for the fixture? I think the ballast has to be matched to the bulb, just as with flourescent lamps. Fred |
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"hungry1" wrote in message news:1103993274.1ab3a0becb9f018c0d9c4d5e6a1108d6@t eranews... Could someone tell me what might be the cause of a mercury vapor light to intermittantly go off and in a few minutes come back on? It doesn't do it consistantly, but rather often. Thanks, -- curt Mercury lamps rarely do this, but I have seen some of the cheap Chinese made lamps cycle when they reach end of life. A guy I know had a 100W one that only lasted 3 months, sure a big step down from some of the 60's vintage Westinghouse and GE lamps that happily ran for 20-30 years. Most HPS lamps will cycle when they age and the emissive material wears off the cathodes, Metal Halide lamps will often suffer an arc tube rupture before this happens, in lighting industry terms a "non-passive" failure but what it usually comes down to is a shower of red hot quartz shards and broken glass. This is why it's important to always have the cover in place when operating these lamps. |
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If it has always done it, could you have the wrong wattage lamp for the fixture? I think the ballast has to be matched to the bulb, just as with flourescent lamps. Yes it does, mercury lamps are quite tolerant of over and under wattage operation compared to other discharge lamps, but in either case lamp life suffers, sometimes dramatically. If the cathodes are too hot they evaporate and blacken the arc tube, if they're too cold they sputter and blacken the tube, either way the lamp lumens depreciate substantially over time while power consumption remains the same. |
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Most of the time this is a sign of the lamp failing. Sometimes it is also
the ballast transformer as well. You will have to try the lamp first. If the lamp is still flickering, then change the ballast transformer. -- Jerry G. ====== "hungry1" wrote in message news:1103993274.1ab3a0becb9f018c0d9c4d5e6a1108d6@t eranews... Could someone tell me what might be the cause of a mercury vapor light to intermittantly go off and in a few minutes come back on? It doesn't do it consistantly, but rather often. Thanks, -- curt |
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"Jerry G." wrote in message ... | Most of the time this is a sign of the lamp failing. Sometimes it is also | the ballast transformer as well. You will have to try the lamp first. If the | lamp is still flickering, then change the ballast transformer. Change the ignitor first. It's easier and cheaper than changing the ballast transformer. That you should be able to test by shorting it with an AC ammeter with the ignitor removed. N |
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"NSM" wrote in message news:_Wmzd.9650$Y72.7767@edtnps91... "Jerry G." wrote in message ... | Most of the time this is a sign of the lamp failing. Sometimes it is also | the ballast transformer as well. You will have to try the lamp first. If the | lamp is still flickering, then change the ballast transformer. Change the ignitor first. It's easier and cheaper than changing the ballast transformer. That you should be able to test by shorting it with an AC ammeter with the ignitor removed. N This is a mercury lamp, they don't use igniters. Only HPS, modern pulse-start metal halide and some modern LPS lights use an igniter. Mercury vapor lamps are all probe-start and rely only on sufficient open circuit voltage from the ballast. Also his lamp is igniting so even if it did use an igniter that's not the problem, if the igniter fails in a pulse-start fixture the lamp will never light. |
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"James Sweet" wrote in message news:Hwqzd.15673$rL3.9038@trnddc03... | This is a mercury lamp, they don't use igniters. Only HPS, modern | pulse-start metal halide and some modern LPS lights use an igniter. Mercury | vapor lamps are all probe-start and rely only on sufficient open circuit | voltage from the ballast. | | Also his lamp is igniting so even if it did use an igniter that's not the | problem, if the igniter fails in a pulse-start fixture the lamp will never | light. He may have mis-identified the lamp type. N |
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"NSM" wrote in message news:dRszd.9681$Y72.7148@edtnps91... "James Sweet" wrote in message news:Hwqzd.15673$rL3.9038@trnddc03... | This is a mercury lamp, they don't use igniters. Only HPS, modern | pulse-start metal halide and some modern LPS lights use an igniter. Mercury | vapor lamps are all probe-start and rely only on sufficient open circuit | voltage from the ballast. | | Also his lamp is igniting so even if it did use an igniter that's not the | problem, if the igniter fails in a pulse-start fixture the lamp will never | light. He may have mis-identified the lamp type. Entirely possible, though that still doesn't change the fact that the igniter is apparently not the problem in this particular case. That is a good point though, the two common types of sodium lights are pretty distinctive, but people very regularly misidentify metal halide lights as mercury. A probe start MH lamp will usually light up fine on a mercury ballast but fail within a couple months. The other way around is acceptable for 175W and larger sizes though. |
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hungry1 wrote:
Could someone tell me what might be the cause of a mercury vapor light to intermittantly go off and in a few minutes come back on? It doesn't do it consistantly, but rather often. Thanks, -- curt Is it possible that the fixture has an overheat switch in it? Many household recessed incandescent fixtures have such a switch, and they sometimes cycle annoyingly (though safely!) Bill Jeffrey |
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On 26-Dec-2004, Bill Jeffrey wrote: Could someone tell me what might be the cause of a mercury vapor light to intermittantly go off and in a few minutes come back on? It doesn't do it consistantly, but rather often. Thanks, -- curt Mercury vapour lights use a gas such as neon to strike a running current limited arc, the lamp starts to heat up, vaporizing the mercury (which at low temps may be solid - mercury theremometers can freeze you know), the temperature and pressure in the bulb rises as the mercury vapour carries the current. If the pressure rises too high for the mains supply to sustain the arc, the arc extinguishes and the lamp has to cool before it will re-start. Then it does the above cycle again. This repeating cycle usually means a defective or worn out lamp. High pressure lighting mercury vapour lamps (in the UK 240v supply) run off the mains through a current limiting choke, regulating the current to 2A or so. Not sure about the lower voltage US mains, they may need some special arrangement to get the arc started. Low pressure mercury vapour tubes (not used for lighting) strike at 1KV or so, and run at typically 100mA from a current limiting transformer called a leak transformer. Leak because some of the primary flux is leaked away through a shunt so as to limit the current. Making it a constant (well near enough) current, high voltage transformer. |
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"James Sweet" wrote in message news:zquzd.3971$Y57.676@trnddc08... | Entirely possible, though that still doesn't change the fact that the | igniter is apparently not the problem in this particular case. | | That is a good point though, the two common types of sodium lights are | pretty distinctive, but people very regularly misidentify metal halide | lights as mercury. A probe start MH lamp will usually light up fine on a | mercury ballast but fail within a couple months. The other way around is | acceptable for 175W and larger sizes though. No replies from the OP so at this point speculation is moot??? FWIW, I always try the easy things first. The other way around tends to lead to much vigorous cursing! N |
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Mercury vapour lights use a gas such as neon to strike a running current limited arc, the lamp starts to heat up, vaporizing the mercury (which at low temps may be solid - mercury theremometers can freeze you know), the temperature and pressure in the bulb rises as the mercury vapour carries the current. If the pressure rises too high for the mains supply to sustain the arc, the arc extinguishes and the lamp has to cool before it will re-start. Then it does the above cycle again. This repeating cycle usually means a defective or worn out lamp. High pressure lighting mercury vapour lamps (in the UK 240v supply) run off the mains through a current limiting choke, regulating the current to 2A or so. Not sure about the lower voltage US mains, they may need some special arrangement to get the arc started. Mercury lamps use argon as the fill gas, and for 120v operation they use an autotransformer ballast just like large (700-1000W) require to run on 240v mains. Low pressure mercury vapour tubes (not used for lighting) strike at 1KV or so, and run at typically 100mA from a current limiting transformer called a leak transformer. Leak because some of the primary flux is leaked away through a shunt so as to limit the current. Making it a constant (well near enough) current, high voltage transformer. SOX (low pressure sodium) lamps use a similar type of transformer, this is why while the lamp efficiency is very high, the system efficiency is rather pathetic for the smaller sizes (15W ballast loss for an 18W lamp!) . Some modern units use electronic ballasts which are more efficient, I'm not sure how much more though. |
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More info on lamp...it's in venezuela with 120v same setup as US. (well
almost). It is a 175W lamp (like a street light) mounter on a pole near the street. It is about 2yrs.old. The light is more green than anything I can describe. (we do have some of themore yellowish lights in some areas, but I think they are sodium).There are some night that the light stays on all night, and yet some nights, it stays on about 10-15 minutes and goes off for 2-3 minutes then back on again....Then maybe it's 2 hrs before it goes off again... or maybe it stays on the rest of the night. Thanks for all of you input. -- curt "James Sweet" wrote in message news:aKEzd.7419$tG3.6042@trnddc02... Mercury vapour lights use a gas such as neon to strike a running current limited arc, the lamp starts to heat up, vaporizing the mercury (which at low temps may be solid - mercury theremometers can freeze you know), the temperature and pressure in the bulb rises as the mercury vapour carries the current. If the pressure rises too high for the mains supply to sustain the arc, the arc extinguishes and the lamp has to cool before it will re-start. Then it does the above cycle again. This repeating cycle usually means a defective or worn out lamp. High pressure lighting mercury vapour lamps (in the UK 240v supply) run off the mains through a current limiting choke, regulating the current to 2A or so. Not sure about the lower voltage US mains, they may need some special arrangement to get the arc started. Mercury lamps use argon as the fill gas, and for 120v operation they use an autotransformer ballast just like large (700-1000W) require to run on 240v mains. Low pressure mercury vapour tubes (not used for lighting) strike at 1KV or so, and run at typically 100mA from a current limiting transformer called a leak transformer. Leak because some of the primary flux is leaked away through a shunt so as to limit the current. Making it a constant (well near enough) current, high voltage transformer. SOX (low pressure sodium) lamps use a similar type of transformer, this is why while the lamp efficiency is very high, the system efficiency is rather pathetic for the smaller sizes (15W ballast loss for an 18W lamp!) . Some modern units use electronic ballasts which are more efficient, I'm not sure how much more though. |
#18
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"hungry1" wrote in message news:1104160346.f0336522e41fc7f27894a0c095875a57@t eranews... | More info on lamp...it's in venezuela with 120v same setup as US. (well | almost). It is a 175W lamp (like a street light) mounter on a pole near the | street. It is about 2yrs.old. The light is more green than anything I can | describe. (we do have some of themore yellowish lights in some areas, but I | think they are sodium).There are some night that the light stays on all | night, and yet some nights, it stays on about 10-15 minutes and goes off for | 2-3 minutes then back on again....Then maybe it's 2 hrs before it goes off | again... or maybe it stays on the rest of the night. | Thanks for all of you input. Up here a .22 will usually ensure prompt repair. N |
#19
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Very true....but I own this one and I'm the one that has to pay for the
repairs! -- curt "NSM" wrote in message news:wwYzd.33181$dv1.21311@edtnps89... "hungry1" wrote in message news:1104160346.f0336522e41fc7f27894a0c095875a57@t eranews... | More info on lamp...it's in venezuela with 120v same setup as US. (well | almost). It is a 175W lamp (like a street light) mounter on a pole near the | street. It is about 2yrs.old. The light is more green than anything I can | describe. (we do have some of themore yellowish lights in some areas, but I | think they are sodium).There are some night that the light stays on all | night, and yet some nights, it stays on about 10-15 minutes and goes off for | 2-3 minutes then back on again....Then maybe it's 2 hrs before it goes off | again... or maybe it stays on the rest of the night. | Thanks for all of you input. Up here a .22 will usually ensure prompt repair. N |
#20
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"hungry1" wrote in message news:1104160346.f0336522e41fc7f27894a0c095875a57@t eranews... More info on lamp...it's in venezuela with 120v same setup as US. (well almost). It is a 175W lamp (like a street light) mounter on a pole near the street. It is about 2yrs.old. The light is more green than anything I can describe. (we do have some of themore yellowish lights in some areas, but I think they are sodium).There are some night that the light stays on all night, and yet some nights, it stays on about 10-15 minutes and goes off for 2-3 minutes then back on again....Then maybe it's 2 hrs before it goes off again... or maybe it stays on the rest of the night. Thanks for all of you input. Sounds like mercury, they do tend to turn a bit more greenish as the lamps age. Look at the arc tube, if it's blackened then the lamp is shot for sure. Replacement bulbs are inexpensive and should be readily available. |
#21
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On Sun, 26 Dec 2004 18:43:17 GMT "NSM" wrote:
FWIW, I always try the easy things first. But, gee, what's the fun in that? ;-) - ----------------------------------------------- Jim Adney Madison, WI 53711 USA ----------------------------------------------- |
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"Jim Adney" wrote in message ... | On Sun, 26 Dec 2004 18:43:17 GMT "NSM" wrote: | | FWIW, I always try the easy things first. | | But, gee, what's the fun in that? ;-) I was half way through dismantling a woman's electric stove once to try to find the source of the smoke she said had come out of it - when she remembered she'd turned it on with a tea towel inside. N |
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