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Matthew Macomber

HMI Bulb Orientation?

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I have an Arri M18 and M8. Can someone tell me as a matter of fact whether the bulbs are supposed to be installed with the internal bar/rod up or down?




Secondly, is it okay for the ceramic base to be cracked? I just noticed this upon close inspection.




And thirdly, is it okay to spray a tiny bit of lithium grease on the rails inside the housing? I'm trying to kill the squeaking when adjusting the focus knob.

Edited by Matthew Macomber

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Osram, Phillips, and Ushio all list their operating positions as "any", though maybe they would tell you something different if you called. It seems to me that the orientation simply doesn't matter with single-ended lamps. The crack on the base of your lamp is certainly not good news, but I would expect the lamp to keep on running for now. Eventually, the vacuum seal of your outer envelope will fail, and so will the lamp. You might notice a white buildup on the glass as the lamp gets worse.


As for greasing the worm-gear of your M18 focus drive, I would say go ahead, but be sure to use a high-temperature lubricant. It is possible that the squeaking is indicative of something other than corrosion of your focus drive. Perhaps the lamp-lock lever has been forced forward or backward by impact, maybe shipping. If that were to happen, the lamp carriage could become twisted slightly. When you move your lamp carriage into full flood position, does the lamp rotate slightly?

Edited by Brian Doran

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Thanks for your thoughts Brian. I won't worry about the bulb orientation until there's further evidence to then.


As for the worm-gear drive in the heads, I went ahead and sprayed a tiny bit of grease on em. They instantly quieted down. I tried to be very sparse on the grease - certainly don't want it catching fire or whatever.

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