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Philips 70w MHN-T Two protected quartz metal halide lamps with PG12-2 caps. The early lamps (along with the SDW-T) featured a while plastic base but this was changed to metal on the later lamps because the plastic tended to discolour when in use. An interesting lamp as it uses thulium, dysprosium and holmium iodides in the discharge mixture. Thulium is quite an aggressive halide and this would sometimes lead to arc tube explosions so two thick quartz shields were employed to allow safe operation. The prefocused PG12-2 cap was selected to ensure excellent optical control when the small arc gap was positioned at the focal point of a reflector.

Philips 70w MHN-T

Two protected quartz metal halide lamps with PG12-2 caps. The early lamps (along with the SDW-T) featured a while plastic base but this was changed to metal on the later lamps because the plastic tended to discolour when in use.

An interesting lamp as it uses thulium, dysprosium and holmium iodides in the discharge mixture. Thulium is quite an aggressive halide and this would sometimes lead to arc tube explosions so two thick quartz shields were employed to allow safe operation.

The prefocused PG12-2 cap was selected to ensure excellent optical control when the small arc gap was positioned at the focal point of a reflector.
DPP8.JPG DPP_3068.jpg DPP_3619.jpg ge250warcztream.jpg IMG_0201.jpg
File information
Filename:DPP_3619.jpg
Album name:FrontSideBus / HID: Metal Halide
Filesize:2061 KiB
Date added:15 Dec, 2015
Dimensions:1920 x 1280 pixels
Displayed:19 times
URL:http://80.229.24.59:9232/gallery/displayimage.php?pid=2474
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Comment 1 to 4 of 4
Page: 1

James   [15 Dec, 2015 at 10:21 PM]
The white-based one also in fact has a metal cap, but its overmoulded with a layer of white polybutylphthalate. The reason for the metal caps on these is because the cement used to bond glass lamps to their caps has to be heat-cured. Normally that is done by heating the cap with gas flames, but that would burn a plastic cap. The metal insert allowed the cap to be heated by radio-frequency induction. Due to the problem of the plastic degrading over life, it was later reduced in size to occupy only the area between the base pins Which runs much cooler than the area lose to the bulb.
AngryHorse   [15 Dec, 2015 at 11:27 PM]
I got 2 of these not long after they came out, cost me something like £140!!
Kev   [15 Dec, 2015 at 11:29 PM]
Why did you do that? Knowing you rich there was some kind of idea behind it?
AngryHorse   [15 Dec, 2015 at 11:44 PM]
They were the first halide lamps I ever got, but I still lived at home then, and had more money to waste! Very Happy

Comment 1 to 4 of 4
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