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

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