Film-Tech Forum ARCHIVE: NEC 1200 Lamp issue

This is topic NEC 1200 Lamp issue in forum Digital Cinema Forum at Film-Tech Forum ARCHIVE.

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Posted by Richard May (Member # 2627) on 05-01-2013, 09:48 AM:

On this particular projector, the lamp power has been fluctuating from day to day. One day it's 73%, the next day it's 86%. Lamp has 1900 hours on it and looks fine. No flicker. Feedback sensor is disabled. Only one movie is playing so it's not a memory issue.

Posted by Gordon McLeod (Member # 33) on 05-01-2013, 03:01 PM:

probably either a ustable lamp or the connections between the lamp and the LPS are having issues what make of lamp

Posted by Richard May (Member # 2627) on 05-01-2013, 04:48 PM:

Ushio UXL-20

Posted by Monte L Fullmer (Member # 2797) on 05-01-2013, 05:26 PM:

I have a 2500 running a 4K lamp that does the same with slight fluctuating amperages, yet no screen issues.

I don't pay any attention to it due to being a xenon bulb where they have their own mind on how they want to run each day.

It also could be your power coming in the building having slight voltage variables were the rectifier amplifies the variables on the DC output.

On the three phase tap in the unit, take a VOM and touch red on each leg and black on chassis to see how each 120V leg is doing. Then red on one leg and black on the other leg to see how the 208V voltage is doing.

Posted by Richard May (Member # 2627) on 05-01-2013, 06:01 PM:

Good point Monte. I'll check the voltage.

Posted by Tony Bandiera Jr (Member # 2365) on 05-01-2013, 06:53 PM:

quote:
On the three phase tap in the unit, take a VOM and touch red on each leg and black on chassis to see how each 120V leg is doing. Then red on one leg and black on the other leg to see how the 208V voltage is doing.

Whoa up there!! Do NOT EVER do what I highlighted!! In the event that the projector is not properly grounded, even the voltage and current passed thru a typical VOM can damage the projector electronics.

When taking AC line voltage measurements, check at the receptacle or panel and use either a proper neutral terminal or proper ground terminal.

Better to be safe in this case.

Posted by Monte L Fullmer (Member # 2797) on 05-01-2013, 08:37 PM:

Thx, Tony for the help.

Should have said, black on Green earth just in case the case isn't grounded.

Posted by Tony Bandiera Jr (Member # 2365) on 05-01-2013, 09:10 PM:

Monte, I hope the tone of that post wasn't as harsh as it looks to me now, I did not in any way intend to impugn your skills. [Smile]

The advice to check voltages was sound. [Smile]

I have found out the hard way (thankfully with a much-less expensive consumer-grade projector) what happens when you use the chassis when measuring line voltages. Luckily the damage wasn't too bad or expensive to fix.

Now, like all rules, there are exceptions....many of the low-voltage test points in a lot of gear does indeed use the chassis as "ground" or "reference" so in those cases your advice was spot-on.

Posted by Monte L Fullmer (Member # 2797) on 05-02-2013, 12:29 AM:

Thx again, Tony. For that is what we are all on here for: to help each other out and get us all pointed in the right direction to where we need to arrive at.

Also, going to mention to Richard, that the xenon bulb is like a big ol' resistor that glows when DC current is passing from one end to the other ... and it's going to act slightly different each day as it ages as the gap between the anode and cathode wears down.

thx- Monte