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Re: [Electronics_101] Re: I need some electrical advice for a Technics SA 404 receiver lighting

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  • Howard Hansen
    Hello Steve, At the bottom of the following web page there is Rapid Lamp Calculator diagram.
    Message 1 of 32 , Apr 28, 2013
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      Hello Steve,

      At the bottom of the following web page there is Rapid Lamp Calculator
      diagram.
      <http://www.intl-lighttech.com/applications/light-sources/tungsten-filament-lamps>
      The diagram allows the user to determine the dependence of Current, Mean
      Spherical Candela and Life on the value of voltage applied to the lamp
      as a percentage of the design voltage for that lamp.

      After looking at the diagram I come to the following conclusions.
      1. Power dissipation is about 55% of the rated power when the light
      output is 1/3 of the rated intensity.
      2. The light output is approximately 10% of the rated intensity when
      the power dissipation is 1/3 of the rated power.
      3. My suggestion to operate the 80 ma and 250 ma lamps at approximately
      equal power levels is a failure.
      4. It is a good thing your were persistent.
      5. Thankfully others have found some micro lamps with a rated output
      close to the rating of the original 80 ma lamps.

      The other Howard


      On 4/27/2013 8:02 PM, raleigh_ranger wrote:
      >
      > Other Howard,
      >
      > > The odor may also be caused by the overheating of the fixture
      > > the bulbs are mounted in.
      >
      > OK good point. If you are sure this is the case I agree.
      >
      > > Instead the power dissipated by 250 ma bulbs should be approximately
      > > the same as the power dissipated by 80 ma bulbs. With approximately
      > > equal power dissipated by both types of bulbs both types of bulbs
      > >will produce approximately the same lumen output.
      >
      > This is the part I do not agree with.
      > As someone else mentioned a 250mA filament will have more mass.
      > If you dissipated the same power through a railroad spike it would not
      > produce light. But a railroad spike will produce light if the amps are
      > high enough. So what resistor would you put in series with a railroad
      > spike to get the same light as a 80mA bulb?
      >
      >



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    • Howard Hansen
      ... Yes you would be safer going under spec. The other Howard ... [Non-text portions of this message have been removed]
      Message 32 of 32 , Apr 29, 2013
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        On 4/28/2013 2:10 PM, Bruzman@... wrote:
        >
        >
        >
        > First off - THANK YOU to everyone for helping me out!
        >
        > Ok - I realize that a 70ma bulb will draw less current than an 80ma
        > bulb. I located a bulb identical in size and shape to the original (8v
        > / 80ma) but it is 8 v / 100ma.
        > Would I be safer going under spec rather than a little over?
        >

        Yes you would be safer going under spec.

        The other Howard


        > The 250ma bulbs I tried had started to darken the pc board and I'm
        > glad I pulled them before the burned up. I don't know why I didn't
        > think of the difference in amperage as causing more draw, more light
        > and more heat - live and learn!
        >
        > I posted some pictures of my "project" thinking it might be easier to
        > solve my problem.
        > http://imageshack.us/g/1/10126479/
        >
        > Again - THANKS for helping the newbie out! I loved electronics in High
        > School and I guess I've got to re-teach myself things.
        >
        > Bruce
        >
        > -
        >



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