Basic questions about HMI lights. (Hot strike) at
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Old May 3rd, 2008, 10:05 AM   #1
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Basic questions about HMI lights. (Hot strike)

I have a friend, through inexperience, who just blew a HMI bulb by trying to strike it the wrong way. It was a 575, but still, those bulbs are mighty expensive. I think he just screwed the pooch and struck a non-strike bulb. Does that make sense? The truck op was too peeved to answer him on what he did wrong, so he's clueless as to how to prevent that from happening again.

I know there's a "Hot Strike" and "Cold" style of HMI bulbs, and there is some issue with ballasts that I don't quite understand, but what I do know is that you can totally bone a bulb with a bad method. Someone enlighten me in English on this, so I will know permanently what a "Hot Strike" is, what the difference is, correct ballast settings, and how I can make sure to not end up like my friend getting funny looks like I'm an idiot.

Is there a "safe" way of starting all HMIs so you're guaranteed not to lose the bulb?
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Old May 3rd, 2008, 02:19 PM   #2
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Here's some thoughts that I had on the subject.

1). Its not possible to mix a hot strike and cold strike bulb as they use different bases (and therefore sockets). A hot strike 575w uses a G22 base. A cold strike version uses a GX9.5. So different that it's impossible to mix them up.

2). Hot restrike capability is murderous on bulbs regardless of whether they are hot strike capable or not. Its tough on all the components in the system from the socket and ignitor to the ballast itself. You're talking about a start pulse of several thousand volts from the ignitor to get it to light. Try to do that over and over several times in a row and you are pushing your luck. IMHO, the safest way is to never really use the hot restart unless you really have to. Let the bulb cool down for at least 5m.

3). I never push hot restart too much as its not completely reliable nor is it safe to over use it too much. Even a hot restart ballast may not light every time and it may be best to let everything cool off a bit. The reason a hot restart bulb has such a short life compared to a cold start one is all this extra stress (750 to 1000 hours for HR vs. 1,000 to as many as 10,000 hours for a "cold" one).
Richard Andrewski - Cool Lights USA - RED #114
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Old May 6th, 2008, 08:33 AM   #3
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575 _double_ ended bulbs do come in both hot and non-hot restrike.

a non hot restrike bulb is around $35, a hot restrike $75-90.

now if this guy kept hitting the start button and fried the igniter, not just the bulb, thats another story.... ballasts don't have any settings besides some that dim, or can switch from 60hz to FF. a few have power settings, but usually they use two connectors. maybe it was a 575/1200 ballast and he flipped it to 1200 :(
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Old May 8th, 2008, 08:08 PM   #4
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I've got a bron kobold 200 and the bulb is looking a little cloudy and has a hard time striking. Is that a sign of the bulb going bad or ballast issues?
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Old May 10th, 2008, 08:38 AM   #5
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If it is possible to generalise, will the lifetimes of bulbs used in hot-restrike capable setups reach the lifetimes of regular bulbs, if they are allowed to cool fully?
Or if I can be fairly confident that I won't be in that much of a hurry, should I go with non-hot-restrike? With the difference in lifetimes, plus the fact that they're nowhere near as bad for raising the temperature, I can afford to leave them on for brief interruptions of filming.
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Old May 10th, 2008, 10:05 AM   #6
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I just would not worry about it. look at it this way

1000hr run time / 8hrs a day = 125 days of burn time. for a 575, a bulb is $80 or so, rental rate runs from $50-$100/day. one day pays for the bulb, the other 124 days @ even $50 / =$6250.... so who really cares once you look at it that way. even a 1200par with a $150-$200 bulb rented at $100-$125/day works out, so gain, very acceptable return on your investment.
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Old May 10th, 2008, 10:46 AM   #7
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It depends on the light, but a 575 for an Arri is around $175.

What Richard said is good info. Just because you can doesn't mean you should. Most HMIs I rent are Arris, from 200 watt to 1200, all are hot strike, but I rarely have done it for the very reason Richard mentions.

As far as your friend's mea culpa, it could be that the bulb was close to the end of its life anyway and that strike killed it, but you'll never know.
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