CFS Lamphouse/Automation (LSX-4500)
Christie CXL-4200A lamp.

It seems to me (us) that we've somehow lost a leg of the three phase power.

I immediately changed all six diodes, figuring it's faster than trying to figure out which one was bad. -- Only got a couple more amps, otherwise, negative result.

Rapped on the power contactor(s) with the handle of a screwdriver, to see if they'd become wedged. -- No jump on the ammeter. Shuting of the breaker and clicking the contactor on/off had no effect either.

Checked all electrical connections: tightened screws/bolts on taps and feeder lines and power cables to lamp. (even used a little sandpaper for good measure) -- Got a couple more amps, but still negative result.

Replaced Xenon lamp. -- Was able to focus it to squeeze every ounce of available light out, but still nothing.

Tomorrow morning, I'll re check the diodes and connections. I'll also try a different tap setting. Maybe there's a bad winding in the transformer?

Our tech wants to order a new transformer but I just wanted to see if anbody has any ideas first. The thing will cost $2,500 and it will take a week to deliver. I'm hoping we can save some trouble.

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Voltage across each diode is about 12VDC.

Didn't check Phase-to-Phase, or across contactor. Will in the morning.

If not,remove the cover from the electrical panel, switch off the breaker, remove the three load wires, switch on the breaker and check (at the load side of the breaker) for 200- 220 volts phase-to-phase on all three legs. ie; Phase A to Phase B, Phase A to Phase C, and Phase B to Phase C should all be around this voltage.

Alternatively, a check from each phase to ground should be around 110 volts.

The reason for removing the load wires is to be sure you are not getting erroneous readings from voltage being fed back,from another phase, through the load.

P.S. It may be possible to "borrow" a breaker from somewhere else in the complex.

Yeah, 104 seems low. That's what I get if I put the meter in the wall outlet, too. Always have. The meter I have is a "True RMS" type. It automatically reads the RMS voltage, not the Pk-Pk voltage.
(I never liked that... At least not for THIS kind of work. I've always done it the way they taught us in Tech School... Multiply by 0.707 or 1.414. -- 9 times out of 10 you want the Pk-Pk in this line of work.)

Anyway, that's what we've always had in this building. All the proj. have worked fine.

There are two projectors on each breaker panel. Each panel has its own disconnect at the service panel in the electrical room. I'm assuming that if it was the feeder that's bad the other projector would have the same symptoms. It is OK.

If the voltage (Phase-to-Gnd.) going into the transformer (downstream of the contactor) is the same as the voltage that's comming into the contactor, doesn't that rule out the contactor?

The last couple of times I had a contactor go bad, I could rap on it with the handle of a screwdriver and the ammeter would jump. (Signaling that the contacts are either wedged or burned.) When I do it this time the meter stays steady.

Tomorrow, when I go in, I'll check all these things. and double check all the things I've looked at so far just to be sure.

BOY! Won't the Cinemark bean counters be PISSED if they have to pay for a new transformer!?

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Tested the incomming line voltage, the lines feeding to the contactor, comming out of the contactor and accross the contactor. Everything was normal, all within a few volts of each other.

Re tightened all the conections again.

Re checked all the diodes. -- All good.

Changed the tap settings. (From "Z-1" to "Y-4") -- That did it! I'm assuming it was a bad, but not yet totally fried winding. It's possible it could have fried on the last show of the previous night and whoever was in charge of the booth wasn't paying attention. (It wouldn't be the first time. )

Anyway, we're not going to tinker with it anymore until our Tech. can get here. Since it's running OK (for the time bering) he's downgraded us from "emergency" status to "get there soon" status.

Thanks guys! In situations like this, two heads are better than one. -- Two HUNDRED is even better.