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Strange Issue With HMI?

HMI Lighting Head Cable

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#1 Blade Mages

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Posted 11 November 2014 - 07:50 PM

Now... I say this is a "strange issue" and maybe it is more common than I think but I'm hoping someone can help me out! 

 

I picked up a used Arri 1200 Compact HMI with a magnetic ballast on eBay a few weeks ago. Today, we were setting up for a shoot and realized a strange quirk with the light. 

 

Just for the record. The lamp is brand new. The 50' head cable is brand new. Fuses are good. Everything seemingly checks out. 

 

So, the problem: With the light attached to the head cable, it will not strike. 

 

The solution: Remove the head cable and attach the light directly to the ballast - turn it on. Voila! It works. We run the light for 2-3 seconds then power off, add the head cable, turn back on. Works fine - the light will run problem free for hours. Right now, we've just determined that the light has "character" and needs a little extra love to work properly. We we're just fortunate to come across this strange fix as we really needed the light for this shoot! Now, we're looking for a more elegant long-term fix. 

 

Any ideas as to what is causing this? Admittedly, I don't regularly work with HMIs - typically tungsten, kinos and LED. Any advice/help is greatly appreciated! 

 

Cheers!


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#2 Stuart Brereton

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Posted 12 November 2014 - 01:43 AM

When you say 'attach the light directly to the ballast' how exactly are you doing that?


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#3 Blade Mages

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Posted 12 November 2014 - 08:06 AM

When you say 'attach the light directly to the ballast' how exactly are you doing that?

 

The light itself has a 18" or so cable coming from it. We just run that short cable directly into the ballast. 


Edited by Blade Mages, 12 November 2014 - 08:08 AM.

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#4 Phil Rhodes

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Posted 12 November 2014 - 08:59 AM

That's so strange it sounds to me more like you're running into a random bad-connection issue that's just coming up sometimes.

 

P


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#5 Guy Holt

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Posted 12 November 2014 - 12:23 PM

That's so strange it sounds to me more like you're running into a random bad-connection issue that's just coming up sometimes.

 

There could be a couple of possibilities:

 

1) the ignition kill switch in the door needs adjustment. It was not engaged the first time, but moving the head around caused it to click in.

 

2) head cable connection was not properly seated so not all the pins were making good contact.  Make sure it clicks into place when making connection.

 

Guy Holt, Gaffer, ScreenLight & Grip, Lighting Rental & Sales in Boston.


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#6 George Suarez

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Posted 13 November 2014 - 01:19 PM

I run a HMI repair shop in North Hollywood called GFS Lighting Repairs.

 

First:

1. Did you hear a loud thump sound when you hit the start button? Since this is a magnetic system you will hear the large contactor inside the ballast engage once you hit start. 

 

2. If No. Then we are dealing with a safety loop issue and you can follow Guy Holts explanation.

 

3. If yes, then it was a failed strike. There are several factors that can cause a globe to fail a strike.

 

But I'm thinking that by plugging the head directly to the ballast you provided it a stronger ignite ( more power since you get rid 50-100ft of resistance in the cables), this jump probably allowed the chemicals and metals in the globe to mix easier. Since it was a newer globe it might of just not been burnt in yet. 

 

If you ever need HMI help over the phone or countinue to have this problem. I offer free help. 818-767-6927 - George Suarez


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#7 Phil Rhodes

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Posted 13 November 2014 - 01:48 PM

I once had an ancient Lee Colortain 1200W HMI PAR that would strike direct connected but not via the cable - reterminated the cable and it worked fine.

 

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#8 Guy Holt

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Posted 13 November 2014 - 03:46 PM

But I'm thinking that by plugging the head directly to the ballast you provided it a stronger ignite ( more power since you get rid 50-100ft of resistance in the cables), 

 

This reminds me of a situation I once encountered trying to strike a CMC Silver Bullet 4k Par. At first the head didn't strike. We eliminated the head cable and patched the head straight into the ballast and it struck. Figuring we had a bad head cable, we grabbed what we knew to be a good head cable from another 4k that had been operating. The head wouldn't strike with the good head cable either. Grasping at straws I began to wonder if the added resistance created by the coil of head cable was a contributing factor. We dressed the head cable in a figure 8 and the head struck without difficulty with both head cables.  Since that day I have always dressed the head cables of larger HMIs in a figure 8.

 

Guy Holt, Gaffer, ScreenLight & Grip, Lighting Rental & Sales in Boston


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#9 Blade Mages

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Posted 15 November 2014 - 07:02 PM

Seems to have been the ignition kill switch - at least I'm fairly sure. I used a little black foil to make a shim of sorts so that the kill switch would be depressed further and the light worked fine. Didn't have time on set to actually fix it but the short term solution help up for two days. Going to adjust the kill switch and hope that takes care of it. 

 

Thanks everyone for the suggestions! 

 

 


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