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Author Topic: Power problem?  (Read 1774 times)

Thomas Lamb

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Re: Power problem?
« Reply #10 on: May 12, 2014, 10:24:58 am »

Did you ask anyone at the theatre if they're been experiencing any unexplained failures of equipment in the projection booth?
That's the question of the day as well as have they had any air conditioning work done or any othe service calls. Ice machines,etc.....
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bigTlamb

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Mike Sokol

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Re: Power problem?
« Reply #11 on: May 12, 2014, 11:05:02 am »

Biulding is maybe 6-8 yrs old. It is 120/208v wye. 16 theaters all digital projection. We run out of the same panel as some of the projectors each projector I presume are 208. However they have racks of QSC CX series amps 120v. Each projector has it's own sub panel mounted in the base of the projector stand.

How many amps are each service panel? 100, 200, ???

I can't imagine that any projector is going to be 3-phase/208, but I've never seen one up close and personal. Anything's possible for 3-D theaters. So does each theater have it's own HVAC powered by that particular service panel?

Tim McCulloch

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Re: Power problem?
« Reply #12 on: May 12, 2014, 11:58:11 am »

How many amps are each service panel? 100, 200, ???

I can't imagine that any projector is going to be 3-phase/208, but I've never seen one up close and personal. Anything's possible for 3-D theaters. So does each theater have it's own HVAC powered by that particular service panel?

It's been a couple of years since I've been in a projection booth, but I recall big Christie projectors and a sub-panel on the wall for each projection station.  Each booth in the complex had its own main panel that handled curtain motors, curtain warmers, auditorium lighting, sound system racks and feeds for projectors.  This was a recent (10 years or newer) build.  I believe the service was 120/208 3 phase wye to each main panel, with  primary distribution of 480v 3 phase delta in the building.

I don't recall auditorium HVAC powered from the panels in the projection booths, but it's possible that the smaller booths had local air handlers; the big booth that served 8 auditoriums had its own HVAC sub system that was independent of the auditorium air.
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Greg Cameron

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Re: Power problem?
« Reply #13 on: May 12, 2014, 03:19:52 pm »

I can't imagine that any projector is going to be 3-phase/208, but I've never seen one up close and personal.

We've got NEC, Christie, and Barco cinema projectors at my day job. They all use use 30A 3∅ wye PSUs, though at lease one has an option for single phase 240.
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Cameron Pro Audio

Mike Sokol

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Re: Power problem?
« Reply #14 on: May 12, 2014, 09:00:14 pm »

We've got NEC, Christie, and Barco cinema projectors at my day job. They all use use 30A 3∅ wye PSUs, though at lease one has an option for single phase 240.
Wow, that's a lotta juice. Is the power supply itself 3-phase, or are the phases split up for fan, bulb, whatever?

Greg Cameron

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Re: Power problem?
« Reply #15 on: May 13, 2014, 01:32:51 am »

Wow, that's a lotta juice. Is the power supply itself 3-phase, or are the phases split up for fan, bulb, whatever?

I haven't torn one down to see. We've got one parked in the hallway near my cubicle. I'll take a look tomorrow to see If I can figure it out.
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Thomas Lamb

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Re: Power problem?
« Reply #16 on: May 15, 2014, 08:00:11 am »

Well I went through all of my PDs last night and everything is fine. Tested it with the shop power source no deviation in voltage. Pulled all the PDs and cables apart and everything was good. So I'm getting into the theatre today hoping for a resolution.
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bigTlamb

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Thomas Lamb

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Re: Power problem?
« Reply #17 on: May 18, 2014, 10:32:16 am »

Well I went through all of my PDs last night and everything is fine. Tested it with the shop power source no deviation in voltage. Pulled all the PDs and cables apart and everything was good. So I'm getting into the theatre today hoping for a resolution.

Ok so when we tested it back at the office when I would flip on the breakers that had the pars hooked up the voltage would jump 2 10ths at the most. I was at the theatre this morning and when untested it there it jumped 3 maybe 4 10ths. So what do I do know? I'm kinda at a loss. I'm thinking ok maybe I did have a bad amp out of the box for the second one but.... It just seems weird. If it was a craptastic amp vs a voltage problem can the repair shop tell that? What do I do know? We are running off a generator this week. Don't really want to do that forever.
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bigTlamb

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Mike Sokol

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Re: Power problem?
« Reply #18 on: May 18, 2014, 11:27:34 am »

Ok so when we tested it back at the office when I would flip on the breakers that had the pars hooked up the voltage would jump 2 10ths at the most. I was at the theatre this morning and when untested it there it jumped 3 maybe 4 10ths. So what do I do know? I'm kinda at a loss. I'm thinking ok maybe I did have a bad amp out of the box for the second one but.... It just seems weird. If it was a craptastic amp vs a voltage problem can the repair shop tell that? What do I do know? We are running off a generator this week. Don't really want to do that forever.

So it sounds like your neutrals are stable, which is to be expected with a modern installation. I don't think that any repair shop is going to be able to determine the cause of the amp failure beyond a WAG, so there's more to think about. Let's boil this down to the basics.

There's really three principal failure mechanisms as I see it.

#1) There's some voltage spike incident that's trashing the power amps.
#2) The amplifiers have a design or build flaw.
#3) You're loading the outputs of the amplifier with too low impedance.

You can rule out #1 by actual testing or historical review. Historically, if other pieces of gear on this power feed have experienced recent failures, then that's the smoking gun. However, perhaps the other gear is more tolerant of voltage spikes (but I doubt it). See if you can rent a power quality monitor for a week or so. Fluke makes some nice ones that will report all voltage over and under conditions as well as log any spike incidents. Something like http://www.fluke.com/Fluke/r0en/Electrical-Test-Tools/Power-Quality-Tools/Fluke-43B-Series.htm?PID=56081 should do the trick.

You can rule out #2 by contacting the amplifier manufacturer or their user forum. Some amplifiers can be a bit sensitive to silly things. For instance, IIRC there was a pro amp design 20 years ago (Carver?) that wouldn't tolerate speakers being connected while the amp was powered up and passing signal. That would trash the output transistors a high percentage of the time.     

You can rule out #3 by double checking all speaker connections and confirming you're not driving too low of a load. And sometimes the load isn't obvious.  I was at a church in Texas a few years back that had a rack full of Crown amps, some of which had blown output channels. Everything appeared to be wired properly and none of the amps was driving under 4 ohms. However, I found one NL4 cable that was improperly wired and shorting between the 1+ and 2+ terminals on one end. This was a bi-amped monitor system so this short in the cable produced a direct connection between the high and low freq outputs of the amplifier. Now how did this problem travel across multiple amps in the rack? Well this cable was used to connect floor monitor speakers every Sunday, so it was wrapped after every gig and hung on the wall during the week. The following Sunday it would be used to connect another floor monitor randomly, thus it eventually found it's way on a bunch of different amplifiers and it would burn out an amp output with any sustained music.

Most apparently random events are not truly random if you can locate what's really changing. 
« Last Edit: May 18, 2014, 01:48:32 pm by Mike Sokol »
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Stephen Swaffer

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Re: Power problem?
« Reply #19 on: May 18, 2014, 06:06:34 pm »

If running on a genny fixes the problem, it would appear that both 2 and 3 are ruled out?  The only difference is the power supply at that point.

Depending on when "this morning" and what else was happening it could be an issue in some other part of the building.  For example, I know that at at our church on a summer Sunday morning, the AC will be running hard for several hours.  If you tested when nothing much was going on, there still might be an issue with harmonics on a neutral once all lighting in other areas is powered up.

Three power supplies in 6 months is certainly suspicious-but consider how many hours you have run without a problem, and how much time you have actually spent with a meter connected.  How likely are you to actually catch an anomaly "in the act"? 
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