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GE MVR250 Metal Halide

Resistor close-up.

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File information
Album name:Paul / Metal Halide
Power Consumption:250w
Cap Type:GES
Comments:Can anyone tell me what this little bimetallic strip is for? It appears to short back through a resistor?
Date / Code:Date code 68
Country Of Origin:USA
Filesize:37 KiB
Date added:Jul 02, 2011
Dimensions:600 x 630 pixels
Displayed:37 times
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Comment 1 to 2 of 2
Page: 1

SuperSix   [Jul 02, 2011 at 10:31 PM]
It might be used to short out the resistor once the lamp warms up.
James   [Jul 03, 2011 at 11:17 PM]
It short-circuits the auxiliary electrode to the main electrode, and has been a feature of all probe-started metal halide lamps since the 1970s. In case the two adjacent electrodes are not short-circuited and the arc tube filling contains sodium, the small voltage difference between them (caused by the probe tip just touching the edge of the plasma) will cause electrolysis of the quartz. That accelerates the rate of devitrification, and leads to weakend quartz and ultimately explosion of the arc tube. This was a serious problem which limited the life of the early metal halide lamps. But by short-circuiting the two electrodes to keep them at the same electrical potential this problem is overcome, and lamp life is increased dramatically.

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