Desisti "Rembrandt" 12K HMI

[Bob Hart]

Time for first try. Switch on. Nothing. Switch off. Switch on again. Nothing. Turns out a little rocker switch, which should switch on, no longer switches on, just feels like it does.

Here's hoping this easy trouble-shoot is not Murphy setting me up for a bigger headache. A bonus really because that switch has never been used in the whole history of the light since I have had it because it is normally out of reach with the lamp on a high stand.

So probably it laid down on being tested for the first time. Hopefully one more little ambush avoided when it counts.

[Chris Medico]

Originally Posted by Bob Hart

Here it is in its skeletal state

You are going all the way. No doubt about it!

[Bob Hart]

The latest in the adventure. There was a dead shutoff switch. The switches in the back of the lamphouse are momentary triggers. One is normally open and connects when operated and signals the ballast to strike the lamp strike. The other is normally connected and opens when operated to signal the ballast to kill the lamp. It is wired in series with the door safety switch.

The second switch is proving to be a mission to find a replacement for. For the meantime I have taken the broken switch apart and repaired it.

Set is all up and tested again. The old globe is really old, as in well past use-by. The envelope is full of dust holes, the gap is wider than it should be and the internal conductors have begun to crack the envelope near the ends. Obviously it should not be used. It strikes but is too much of a burden on the ballast which will drive it for a while but eventually will trip, not a good way to be treating an electronic ballast.

So having got the test out of the way, with everything nice, clean, shiny and well connected, the new globe could go in. - Wrong move. The new globe was gassy, went black in a heartbeat and would not strike at all.

When I bought it, I thought "GE, a good reputable US brand". Yep. Let's get this one. Then I discovered the globe is by an outfit called Koto. Any warranty is way expired as the globe has been stored for three years. Any chance of getting a replace by good grace is also gone. The Outfit "Koto" appears to be no longer making the item. No prize for guessing why.

So, any recommendations on 12K HMI double-ended globes, which are not about to lay down. They are a bit too expensive to be buying as garden curios or cute pretties to park the mantle shelf as novelty ornaments.

[Bob Hart]

The long road is done. The appliance is closed up and the yoke back on without any spare parts that were not replaced on purpose. A bonus was that a "spare" part found inside the electrical enclosure was in fact the missing anti-friction bearing one of the yoke pivots. Now to build some funds for a replacement globe.

[Bob Hart]

The reflector did not look quite right. The four tiny screws which hold it to the frame are 3mm. One screw on being unfastened turned and turned and turned and turned but come out it wouldn't. The reflector looks a bit dented and gouged, so may have been straightened out after a bulb explosion. The dodgey screw turns out to be a something from somewhere else. It seems it was forced. Out with the 3mm x 50 thread tap and four new screws later. Add two 6mm dome nuts to the back of the spot-flood carriage where uncovered sharp screw ends had worn through one of the old cable sleeves. Some stove window gasket to remount the fresnel glass and a lick of paint and the door's done. Lots of evidence of past hasty patchups and gettum-goes. I guess that happens over thirty years of use.

[Bob Hart]

THE 12K HMI LAMP SAGA. CONT'D.


There was an apparently insoluble problem encountered and one knew not which way to turn. It looked like being expensive. However the guru of all things "Lightmaker" branded, Gilbert Navarro of Galaxy Repair Service in the US west coast, generously put me right on track to getting it fixed.

So it lives again to burn moths another day. A double-bonus. A breeder rat has been hanging around this past two weeks or so. It has been trying to eat its way into the lamphouse through sheet metal to get at the nice new glassfibre cable sleeves for nesting material. It met the electric trap last night. So what sort of a bizarre world is it when you end up using a 12K lamp for rat bait?

As another bonus, the three years old G.E. globe, which was thought to be a dud from new, apparently was just a hard starter and has also come good after a fair few tries to light it up. The hard start in combination with the other glitch is what caused it to be apparently moribund. So fair's fair. It should be said, the G.E. globe has turned out to be okay.

[Bob Hart]

It lives. Local friend checking the lamp with his colour temp meter.

12K HMI LAMP COLOUR METERING TEST - YouTube

[Bob Hart]

The final installment,the lamp on a production meeting its purpose and without being consumed by catastrophe.

There is implied non-disclosure regarding the project, an indie being filmed in Western Australia. This much by way of image can do no harm.

Thanks again to contributors of advice and knowledge here at dvinfo and at reduser for making this happen.

All the best for the New Year one and all.

[Bob Hart]

A few months down the track and the edit of the indie movie "3RD NIGHT", for which I was tasked to shoot some BTS footage is now closer to lock off. This is the project the Desisti HMI lamp was restored for. Most of the exterior night work was lit with 1.2K, 2.4K HMI and a selection of modern LED lamps which worked a lot better than I thought they would. The big Desisti was used for moonlight effect on large areas for a few shots.

Here is the first teaser.

3RD NIGHT MOVIE OFFICIAL TEASER TRAILER 1 - YouTube