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Quartz halogen tube failures

Discussion in 'Repairing Electronics' started by paradigm, Jun 1, 2017.

  1. paradigm

    paradigm New Member

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    Hello, I have had a number of quartz halogen tubes failing after a period of service of only very occasional use. The type is the standard 240V, 400W, 117mm linear with R7 end contacts used in standard fittings with a glass front and situated outdoors. There is no question of contamination by finger grease. The consistent thing is that the filament always looks intact and in excellent condition and yet the tubes are open-circuit. I suspect that the failures may be due to corrosion inside the R7 ceramic end fittings. There may also be an internal fuse of some kind?

    Can anyone suggest what the failure mechanism might be and how to avoid it? Although the tubes are cheap enough to buy they are in very awkward places to reach. Thanks for any experience or knowledge of this issue.
     
  2. ci139

    ci139 Active Member

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    there is some about on pg.27 (54)
    -- i'd speculate the poor contact , poor contact design , poor contact material induced sparkling , deviation from expected operating mode are to blame here
    -- also , from personal experience , the lower wattage bulbs ! seem ! to survive longer ? perhaps switching to double your no. of 175 - 230W ones requires less attention ... perhaps
     
  3. KeepItSimpleStupid

    KeepItSimpleStupid Well-Known Member Most Helpful Member

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    Bad batch of bulbs. It happens. Switch brands. Otherwise vibration is the first suspect.
     
  4. dave

    Dave New Member

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  5. ci139

    ci139 Active Member

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    another question is how many lights do you have ? like enough to set the grid waving at simultaneous switch on
     
  6. paradigm

    paradigm New Member

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    Thanks for all the interesting suggestions.

    There is no question of poor or unreliable contacts - the tubes are in excellent condition with clean contacts and intact-looking filaments but they are open-circuit. Due to the awkward location of the fittings I switched to premium brands hoping for greater reliability but the results are the same. Vibration would not seem to be a factor either - the filaments look intact and the R7 end caps are not loose or damaged.

    I only have 4 units but the issue seemed puzzling enough to raise here! Looking on the Internet, this does not seem to be a general problem - maybe I should consult the manufacturers? I read somewhere that these tubes have an internal fuse. I must look into this further as I don't think it is usual for bulbs/tubes to incorporate fuses? I will report back if the root cause can be discovered.
     
  7. GromTag

    GromTag Active Member

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    Is there any kind of Ballast transformer in line to the tube housings?

    Also possible loose wiring can cause shorts such as an arc jumping an loose contact causing erratic supply, however the loose wire should be placed as a possibility if no Ballast of any kind is equipped, or transformer of any type. Just that the loose wire concept would be difficult to trace and may not be an likely culprit. So the loose wire concept would be best to place latter on the list depending on difficulty at getting to the wires to the housings them selves not wanting to cause more of a possible problem if it turns out not to be the wiring. (typically junction boxes, ore loose connections at the breaker connections within the breaker box)

    Rating of the main breaker sufficient? or its condition?

    Any other lighting that is not resulting in bulb fault if available else where showing any dips or buzzing sounds when in use?
     
  8. paradigm

    paradigm New Member

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    Thanks. There is no ballast/ transformer and I do not suspect the wiring or breaker in this instance.
    I found some information on the internal fuse in a Philips document at:

    http://www.lamptech.co.uk/Spec Sheets/TH DE Q300T10C-245 Fuse Chamber Philips.htm

    The fuse is intended to blow after a filament failure when a high arc current may flow. However this does not seem to be applicable in my case. I must have a good look at the filament under a microscope, especially the ends - something in the tubes is going open-circuit!
     
  9. GromTag

    GromTag Active Member

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    Does the documentation state that the fuse method was used up to the early year 1990's then another method adopted?

    Unless you have tubes from the prior to early 90's that is?

    Restatement of the documentation:

    Other info states bromine gas and iodine was the final employment then the bromine - iodine gas started to shorten life via corrosion and caused an angle of operation limitation of the tubs use at ± 4° horizontal via the iodine thus resulting in an final use of bromine gas only as the final design in documentation.

    Am wondering as to the fusing method if what "simpler method" as in is there still a fuse like device in newer types? If those tubes you have now are more recent.

    Well regardless, if it matches close to the images in the documentation then chances are it would be identical in resulting a find to the cause.
     
  10. GromTag

    GromTag Active Member

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    Also, if not known, if the checking may result in tube breakage, an out side setting would be helpful as bromine in adequate amount can be hazardous. Tho the amount would have to be considerable. Also it is surprising what bromine can be found in, even food products....
     

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