HMI705 in place of a MSR700S/A?

[TimMiller]

I was replacing some lamps and i realized our lamp place sent us HMI 705, which is a 700W single ended HMI lamp. It looks just like the S/A. I then asked the person who ordered them whats up with these and they told me that they were told by the supplier that they would work and they were about 30 bucks cheaper. So i figured what the heck, and threw one into a test fixture and it fired up and ran for a good hour with no explosion. But before actually replacing my rental unit lamps with HMI's what is the difference? The strike voltage and operating voltages were the same. I know ship will have an answer. I am guessing a color temp difference?

 

[SAWYeR]

I think (and I very well could be wrong) that a major difference between HMI and MSR-type lamps is the gasses that are used inside the globe and the outer tube. We have an Arri Sun HMI fresnel here at my school ( I think it's a 705) and I know that the color temperature is somewhat different to that of the usual MSR lamp that most movers use. But other than that I don't know. If it ran for as long as you said without problems I can't think of anything else to say. Except I always think of HMI lamps being used mainly more in larger fresnels and more movie-based lighting equipment, and also in streetlights if I'm not mistaken. Streetlights use Sodium vapor lamps (orange) and Mercury vapor lamps (white), and the Mercury vapor is close to an HMI lamp. I'm surprised that an HMI worked in place of an MSR though. Learn something new everyday though, right?

 

[JD]

Street lights- Not so much Mercury Vapor but Metal Halide lamps, which are basically long arc low pressure HMIs. There is a big problem with color balance between batches of MH lamps, and the same thing shows up sometimes in HMI and other multivapor arc lamps. The trick is to relamp in batches with the same date code and manufacturer. As for the MSR / HMI, there are quite a few things to check, such as LCL, amps, volts, temp, etc. The best thing to do is get the word from the manufacturer.