Film-Tech Forum ARCHIVE: NC-900 Vertical Lens Shift Failure

This is topic NC-900 Vertical Lens Shift Failure in forum Digital Cinema Forum at Film-Tech Forum ARCHIVE.

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Posted by Mark Gulbrandsen (Member # 72) on 07-10-2014, 02:23 PM:

I've had two NC-900's lens shift mechanism's go all the way up or down and get stuck there. Warranty service fixed one I have to fix the other.

Beware! There is a wire going to the vertical positioning motor on the lens mount from the driver PCB that is likely to be pinched, especially on projectors delivered before the service bulletin. I found my wire jammed in between the spongy grounding material and a metal shield. There is a fix for it and the factory has been clipping the wire in a new position to the metal shield so this can't happen. When it gets pinched it shorts out the driver IC on the lens control board and puts the driver amp way out of balance causing the lens to go all the way up or down depending on failure mode. Those with early NC-900's may want to have their tech get a copy of this bulletin from NEC and check your machine to be sure it is not going to happen. Removing the lens mount in this projector to repair the pinched wire is a bitch! And above all do not install a new lens driver board until you know absolutely the wire is not pinched. It will blow the new board instantly.

If you're comfortable with SMT soldering the IC looks easy to replace and In the future I'm going to carry a half dozen of the $2.00 IC's (L2726) in my tool kit and fix the boards in the booth on location instead of waiting for a replacement board to arrive.

Note that you can keep the projector on screen by raising either the back end or the front end of the projector with 2X4's to keep the unit on the screen.

I found the black wire in this one pinched down by the motor.

Mark

Posted by Steve Guttag (Member # 268) on 07-10-2014, 06:52 PM:

Thanks for the heads up Mark! Thankfully, we don't have any early NC900s.

Note, I looked for the bulletin regarding this and didn't see it. Is it posted?

Posted by Ian Freer (Member # 1940) on 07-10-2014, 08:51 PM:

On the topic of NC-900 lenses, has anyone experienced an NC-900 lens ZOOM function stick? I have two particular projectors where this has happened.
When changing to Scope, the shift and focus functions work but the zoom does not, so Scope ends up as a small image within a larger screen after the masking has opened.
The projector/DCC does not report any error.

The simple fix I've found is to take the front cover off, then change between flat/scope while giving the zoom-ring a little jiggle for a second. This free's it up and it then operates perfectly for many months.
(Note: for those that don't know, taking the front cover off will activate a physical tamper alarm that will need to be cleared by a tech).

One site has had it happen just once, the other has had it occur about three times on the one projector. (Both PJ's have been installed for around 9-12 months).

I cannot recall now if the Flat position is at one extreme end of the zoom range. If it is that might partially explain why it sticks, but I'll need to double check that next time I'm on site.

Cheers,
Ian

Posted by Mark Gulbrandsen (Member # 72) on 07-10-2014, 10:06 PM:

I'll send the bulletin to you Steve...

First you need to be sure the projector has "learned" the lens. Some tech's overlook this. I had the motors on one lens die but NEC replaced it pronto. You should have your technician look at yours...

Posted by Ian Freer (Member # 1940) on 07-11-2014, 01:14 AM:

Hi Mark

The lens was definitely calibrated during installation. I don't think I've missed a lens calibration yet. (The Setup Date, now that's another story... I missed setting that a few times in the early installs...)

Cheers,
Ian