MH lamp dimple

[CSMReef]

Is the dimple on the metal halide lamp suppose to be up or down?

Thanks for your help!

CSMReef

[DarG]

Nipples up :D

Im not sure it matters, usually anyway. Some people swear that it does. There was a thread here this morning where somebody stated that the colors were WAY off if the nipple was down.

I use DE and have never seen a difference in the 150 watt DE's that can be oriented either way. In the 250 watt DE you dont have a choice. I have a bulb pair now where one is up when installed in the socket and the other is down. Actually two pairs like that. Apparently the 250W DE bulb manufacturers, some of them anyway, dont even worry about it when orienting the contacts on the bulbs. Maybe it matters more with SE ...

Anyway ... common wisdom says nipples up.

[CSMReef]

I believe it's because the gas in the bulb won't burn correctly if it faces down... but I could be wrong.

[tadashi123]

phoenix bulb instructions for 250 DE says to install dimple up as doing otherwise may cause premature color shift, or decreased bulb and/or ballast life. i have never tried installing dimple down so i have no reference for comparison. hope that helps

[CSMReef]

Thanks for the responses DarG and Tadashi.

[DarG]

<a href=showthread.php?s=&postid=11995171#post11995171 target=_blank>Originally posted</a> by tadashi123
phoenix bulb instructions for 250 DE says to install dimple up as doing otherwise may cause premature color shift, or decreased bulb and/or ballast life. i have never tried installing dimple down so i have no reference for comparison. hope that helps

Then they better make the bulbs so that the contacts orient them nipple up. You dont have a choice on how to orient the nipple on a bulb with a FC2 "base". That is the 250 and 400 watt DE. They only go into the socket in one direction.

BTW, my Iwasaki 150 watt DE's have arrows on the contact insulators pointing to show the direction of orientation in the socket ... it is nipple up.

Youre welcome CSMreef.