ECN Forum Forums General Topics of the Trade General Discussion Area The great Xenon power supply caper....

naperville:


Naw, you're not. But I have met Rob Reiner, lol.


Funny you should mention that. My next plan of attack was to be to add a relay with a 120vac coil, drive that from the control line from the lamp and then drive the power supply from one of its own phases. But the factory engineer swears that the control can be driven with 120vac from anywhere, it's supposedly completely isolated from the power supply's mains. And he agrees that there is a control board problem. Go figure.

Hi Joe:

Yeah, this thing is a stumper. To explain the hookup:

Each lamphouse is powered on a 20amp 120v circuit. This feeds power to the lamp's blower, high voltage ignitor and also the control circuit, after satisfying two safety interlocks. There is a double-pole switch on the lamphouse that kills power to the control circuit and ignitor when it is off, this is the switch the projectionist uses to control the lamps.

The control circuit sends the 120vac to the power supply "contactor" (in this "new and improved" version, it is a solid state circuit driving first an scr then a high-power triac array to heat up the supply.) The control circuit is designed to turn on with an input voltage range of min. 90 volts and max of 135 volts. See my first post for the measured voltages with the lamphouse switch "on" and "off".

The supply itself has a 208v, 3 phase input on a 30 amp 3pole breaker. This breaker in some installs is left "on" all the time.

So in summary, each lamphouse has its' own 120vac feed and each power supply has its' own 208 vac input. Edited to add: All these circuits are in the same panel.

The fire alarm cutoff is a simple set-up. Inside each lamphouse I have a 24vdc 4pdt relay. The normally closed contacts of this relay are in series with the 120vac hot control line. When the alarm is activated, this relay pulls in and interrupts the control circuit.

The 24vdc comes from the master projection control system (another major PITA, it is a homebrew from a former studio engineer and has lots of bugs.) The control system DOES NOT control the lamps.

The fire alarm system has dry contacts which are normally OPEN, and CLOSE and maintain in an ALARM condition. Resetting the alarm opens these contacts.

So the alarm system isn't part of the problem. If it were to chatter, the result would be that the xenon power supplies would shut down and lock out on their "multiple ignition failure" mode.

Bear in mind that even after I pulled my fire alarm cutoff relay, and even disconnected the control leads altogether, that blasted supply wouldn't shut off!!

***Update: I was back there today on another issue, and when tested the power supply worked properly for the first several rapid on-off cycles. But after it was left "ON" for about five minutes, it would fail to shut off again.***

The sad part of all this is that, despite the cost of this equipment, this manufacturer has always had serious quality control issues. The early generation switchers I mentioned above always had one of four "operation" modes:

It would work great, for about a few hundred hours or less, then quit;
It would work great and run virtually forever; (I actually have one on my home projector)
It would fail right out of the box; or
It would work for a few minutes, then literally go down in flames.


I can totally relate!! I can't go to movies anymore, I'm so programmed to watch for the wretched cues even when I'm sitting in a full house of people. That, and if there are ANY technical flaws in the presentation, I go ballistic.

I once got a house of over three hundred people refunded due to the total ineptitude of the alleged "projectionist" at a very major and famous theatre in Hollywood.

But that's a whole 'nother story.

edited to respond to napervillesoundtech

and to add panel comment




[This message has been edited by mxslick (edited 11-21-2006).]