Arri HMI lamphead

JD Hartman · December 22, 2010

Had a problem with an ARRI 2.5/4K HMI PAR lamphead on my last shoot. This one: http://www.arri.de/lighting/americas/hmi_pars/arrisun_4025.html Fixture which was working the previous day, would not strike, despite swapping the ballast or head cable. The 4K globe appeared fine, supply voltage normal (120VAC). ARRI ballast powered up, but the LED indicators for 50Hz, 60Hz and Flicker Free would not light up regardless of switch setting. Finally noticed that the switch on the lamphead which sets the globe focal point (2.5 or 4.0) had been moved to the 2.5K position by someone. When it was moved back to the 4K position, the ballast "came to life" and the head stuck. Never having seen the internal structure of this lamphead, is that switch purely mechanical or does it also tell the ballast which globe is being used, via one of the head cable pins?

Frank Kistemann · December 24, 2010

What could be mistaken as a switch on the left side of the lamphead is actually the knob that tightens the lamp socket and holds the bulb firmly in place. Fully tightened, the little handle on the knob is more or less vertical and if you turn it counter-clockwise to open the socket, it turns about 90 degrees to the left, maybe even less (hence the potential to be mistaken as a switch). So if that knob wasn't completely vertical, it means that the socket wasn't fully closed and therefore couldn't properly establish contact.

Btw, the focusing knob is on the back of the fixture and as the socket's tightening knob obviously moves with the globe, it indicates the focal point position for each sort of globe (2,5K/4K) respectively.

Merry christmas,

Frank

JD Hartman · December 24, 2010

Thanks for the information Frank. Very little is said in ARRI technical document. The "switch" is supposed to have a hinged cover over it to prevent exactly what had happened, but was missing from both heads. I was not the person to discover the problem, I was checking connections and taking voltage readings at the time. This still doesn't explain the lack of illumination of indicator lights on the ballast. Even with the socket closed, the globe being an enclosed arc lamp would still read as "open" to any monitoring circuit.

Frank Kistemann · December 29, 2010

This still doesn't explain the lack of illumination of indicator lights on the ballast. Even with the socket closed, the globe being an enclosed arc lamp would still read as "open" to any monitoring circuit.

You're obviously right on that one, seems that I wrote a bit too fast for my brain to carry up ;) ... but next time I use an Arrisun I'll definitely check out if the ballast is able to recognize the lamphead when there's no bulb installed, or when the locking knob is left open.

About that hinged cover...it's missing from at least a third of all the Arrisuns I got to work with. It just seems to be a piece that cracks and gets lost once in a while, due to careless charging and rental houses don't seem to bother to replace them. Btw, if I recall correctly, there's a little drawing on the front of that very cover, which clearly identifies the underlying "switch" as the lamp locking knob...

Frank

timHealy · December 29, 2010

but the LED indicators for 50Hz, 60Hz and Flicker Free would not light up regardless of switch setting.

I don't have one right in front of me but off the top of my head, the led lights on Arri ballasts tend not to be on unless the lights are connected and the switch on the ballast and and the switch on the head are in the on position. I'm not talking about the bulb tightening knob on the side of the head. If you plug in the ballast and switch just the ballast on, I believe the default position for the led's is off. However I think there is a power led which shows power is supplied. I'll revisit on my next day of work after the holidays. Also dimmers on Arri HMI ballasts don't really work until the head is sufficiently warmed up.

Also the microswitch for the lens needs to be engaged for the leds to light up and the light to actually work. Sometimes they get banged around and get misaligned.

Best

Tim

JD Hartman · December 30, 2010

Ballast, as stated, powered up, head cable connected, switch on head in "on" position, door on head properly closed, no lights. Head cable swapped, no lights. Head directly connected to ballast, still no joy.

timHealy · December 30, 2010

Ballast, as stated, powered up, head cable connected, switch on head in "on" position, door on head properly closed, no lights. Head cable swapped, no lights. Head directly connected to ballast, still no joy.

Were you able to swap ballast too?

Micro switch problem?

One way to test the micro switch is to open the door to the lamp with it plugged in and switches on and then press the microswitch. If it comes on there you go. If not then there's another issue.

I assume the bulb looked OK?

Tim

PS how was this powered up? Generator or tie in? Some people have trouble with 4k's on certain legs of genny. Sometimes switching the phase will work. Maybe Guy Holt knows of this issue and the why.

Edited December 30, 2010 by timHealy

JD Hartman · December 31, 2010

We had two 4K HMI's. Both ballasts and many head cables were available. The second head was out on a roof and unavailable for observation. Both heads had performed flawlessly for the past 6 days, running off a single phase generator, globes were okay, not many hours on them. The head in question was displaying some electrical issue, but I was never able to determine exactly what. I was checking connections and making voltage reading when the head finally struck. My original question, still unanswered, relates to the guts of the lamphead, does the knob which opens the lampholder and sets focal point of the lamp also serve some additional function? Could it also serve as an electrical switch, which is wired in series with the door safety switch? Something was preventing the both ballasts from seeing that the lamphead was ready to strike. I guess I will have to get that answer from ARRI.

timHealy · December 31, 2010

Could it also serve as an electrical switch, which is wired in series with the door safety switch? Something was preventing the both ballasts from seeing that the lamphead was ready to strike. I guess I will have to get that answer from ARRI.

my professional guess is the bulb tightening knob is almost certainly just that. most hmi's will try and strike without a bulb in the head. but call Arri if you want to be sure. they are just up the road in Blauvelt NY. if they tried to wired something up in there that would be a recent addition to the technology. i would think the engineers would laugh and just say why would we need to put a device in there to defeat the lamp if a bulb wasn't in there when, if there wasn't a bulb in there, then that would defeat the light from coming on just as well. the electricians would figure out a bulb was missing soon enough. did anyone follow that?

the micro switch on the door however will prevent the light from operating if misaligned or the safety glass is not present.

do you recall if anyone tried playing with the micro switch during your trouble shooting?

Edited December 31, 2010 by timHealy

JD Hartman · January 1, 2011

I'm certain that the door was checked more than once. Why would there be an electrical interlock as part of the bulb tightening knob, wired in series with the door switch? To prevent the arcing that would occur between the contacts in the socket and the pins on the globe if the the lamp tightening knob was not in the fully closed position. They might also build it into the head, knowing that somewhere, some rental house would remove the protective metal guard over that switch, leaving it exposed to mishap or a curious crew member. When I have an answer from ARRI, I'll post my findings.

timHealy · January 2, 2011

I'm certain that the door was checked more than once.

it's not the door that needs checking it's the micro switch mechanism or the plunger making contact with the door or the safety glass that needs checking.

timHealy · January 2, 2011

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Edited January 2, 2011 by timHealy

JD Hartman · January 2, 2011

it's not the door that needs checking it's the micro switch mechanism or the plunger making contact with the door or the safety glass that needs checking.

Sorry, in my reply I sometimes forget that we're working in an art form that has components of Science and Engineering. We didn't merely check to see that the door was closed, but did check the mechanical action of the micro-switch and its activation by the door. To do more than that (test electrical continuity), would have required either probing the connector on the head cable with a meter (which I had) or disassembly of the lamphead. Neither seemed possible at the time, as the director was screaming about losing the location in an hour. As I previously stated, the problem disppeared, while I was checking checking in our power distribution.

Edited January 2, 2011 by JD Hartman

JD Hartman · January 4, 2011

Confirmed by the ARRI service department in Blauvelt, N.Y., the lamp lock/position knob on the head does incorporate an electrical switch wired in series with the door interlock micro-switch. Also found out that the metal cover over the lamp lock was an update on the 2.5/4.0 PAR heads, which explains why neither of the heads we rented had it. So if the head won't strike, check to see that the lamp lock switch is fully closed.