Barco DP-2k Image Problem

[Steve Guttag]

NEC is the least precise and the S2K projectors (NC900, NC1000, NC120x and any other based on the .69" chips that use those lenses can't hit their marks...EVER...they are always pixels off...which can be inches on the screen. The NC1200/NC2000 take forever to move their lenses between formats ("Wait a Moment") as it seems to find where the lens is by zooming, shifting then moving to the new position. It's, typically a 10-15 second ordeal. NEC has a "Calibrate" and "Center" setting on the install tab of most/all of their machines. It is worthwhile to calibrate the lens before commissioning the projector. The lens is going to drift over time. I have not found that "Calibrate" really restores it.

Periodically, all projectors need their lenses recalibrated, if the lens is moving between formats (constant height screens).

[Marcel Birgelen]

Jim, The lens controller on the NEC is not really a true servo. It does get feedback but not from a generator on the same shaft per say, but in the form of electrical impulses off the motor commutator. If you examine the control board and things on the lens mount you will only see two wires to each motor and no other means of feedback. So that leaves either brush noise, or time as the feedback factor. There is a lot of stuff on the lens driver board...

Brush noise seems a bit too unreliable to me, especially if you factor in that over time, you'll face different types of motors. Given the general inaccuracy of NECs zoom, you'd say the controller action is only time-based. A real servo would've cost just a few bucks more or a rotary encoder in the lens could also do the trick.

Still, it's crazy how much stuff there is on that controller board and how much interconnects it has, if it's just a simple time-based mechanism...

[Marco Giustini]

"homing" a lens is a must on Barco and Christie. As Leo pointed out it takes a few seconds and must be done if the lens is touched/removed. (Cover your ears when "calibrating" a Christie ILS...)

It's honestly a must before servicing a projector - which should include removing the lens, inspect and clean if necessary BTW. The lens files might/will drift over time and if you don't reset the lens before do final adjustments you're just adding to the pain of the next engineer who might reset the lens only to find that suddenly the projected picture now sits on the ceiling.

[Mark Gulbrandsen]

Brush noise seems a bit too unreliable to me, especially if you factor in that over time, you'll face different types of motors. Given the general inaccuracy of NECs zoom, you'd say the controller action is only time-based. A real servo would've cost just a few bucks more or a rotary encoder in the lens could also do the trick.

Still, it's crazy how much stuff there is on that controller board and how much interconnects it has, if it's just a simple time-based mechanism...

Exactly! And their lens adjusters are not 100% reliable and also drift a little over time. But with proper filtering of the brush noise, it is possible to use it.

[Kevin Roudebush]

Thanks for everyone's input. Definitely the lens. Looking now for someone that can take it apart, clean it and put it back together. Know anyone?