Film-Tech Forum ARCHIVE: nec900c zoom problems

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Posted by David J Hilsgen (Member # 2614) on 10-02-2015, 04:02 AM:

Lens zoom failure, stays in flat any ideas shows scope on the menu screen, took lens in/out did'nt make a difference i'm thinking that motor on the side of lens

Posted by Ian Freer (Member # 1940) on 10-02-2015, 05:47 AM:

It could be a motor failure, but I've had a similar thing happen on a couple of different NC-900's.
In my case, simply "helping" the lens zoom seems to get things back on track.
I.e. Take the front cover of the machine, press the SCOPE button on the side panel and jiggle the lens a little. Press the FLAT button and jiggle the lens again.

I don't know what is actually causing the issue, but gently rocking the lens zoom mech while driving it to flat or scope seems to sort it out.

Sorry I don't have a more technical description, but it really has been a case of just helping the zoom mech while the lens is trying to move between flat / scope that seems to help.
NOTE; If you remove the front panel you need to know the tamper clearance password...

Posted by Steve Guttag (Member # 268) on 10-02-2015, 07:11 AM:

It is also best to never be at the extreme of a lens (or shifter's) range. On an NEC, you are supposed to check on the shift to ensure you are in the shift range before saving the preset (it will say out of range if you are not...but you actually have to tell it to check).

Posted by Carsten Kurz (Member # 5396) on 10-12-2015, 05:22 AM:

Some early production NC900C had a misplaced lens motor cable that could become damaged after repeated lens change operations. NEC has a technical paper on it. Typically, with the defect, the motor driver board will be burnt, and either the driver IC or the whole board has to be replaced. Wether this is the cause of your issue, I don't know.

- Carsten

Posted by Mark Gulbrandsen (Member # 72) on 10-12-2015, 12:34 PM:

Well, the forst thing I;d do is test your lens in another NC-900. Otherwise what Carsten said! There actually exists a tech bulletin on this shorting issue. If the cable shorts it blows out the lens motor driver chip. USUALLY causes the shift to run either completely up or down though. Pull the top (if you are qualified) and carefully inspect the board that's on top near the front of the projector for burn marks right on the chips. You must repair that cable before the lens driver board is replaced or you will also immediately blow a new board!! I've this failure mode happen on two of almost 40 NC-900's I've installed. Getting to that wire that shorts is a bitch! Replacing the lens mount or repairing the wire is even more difficult!! Some major disassembly required.

Mark

Posted by Steve Guttag (Member # 268) on 10-12-2015, 02:45 PM:

Oddly enough, NEC doesn't post the tech bulletin on this one.

Posted by Mark Gulbrandsen (Member # 72) on 10-12-2015, 03:24 PM:

I am sure I sent it to you. It's from Wrong, not Right.

Mark

Posted by Steve Guttag (Member # 268) on 10-12-2015, 07:58 PM:

I might have it...I was noting that it is not on the NEC site in the tech bulletins for the NC900.

Posted by Mark Gulbrandsen (Member # 72) on 10-12-2015, 10:13 PM:

You are correct!

Posted by Carsten Kurz (Member # 5396) on 10-13-2015, 07:32 AM:

I was discussing this issue with a german NEC integrator. He had never heard of the issue and said NEC wouldn't know about it. It seems indeed that the only reference to it come from 'Wrong'. Mark sent the file to me then, thanx for that.

Talked to a german NEC service tech later and he told me he already had serviced a couple of machines with this fault.

- Carsten

Posted by Mark Gulbrandsen (Member # 72) on 10-15-2015, 03:53 PM:

Thankfully it is not a very common problem because for NEC Warranty they send out a new lens mount and that thing is a bitch to replace!

Mark

Posted by David J Hilsgen (Member # 2614) on 10-16-2015, 05:17 AM:

Thanks everybody for your help,i Switched the lens between projectors ,there 3 900s in this theatre & it don't work in the other projector either then i took one that worked & put in that projector w/ the lens problem & it worked were the other lens did'nt i'm just waiting for a response on warranty from nec but i,ll check the wiring by those motors.but like you guys said, if it would of, chewed up those wires it would of burned the lens driver board.

Posted by Carsten Kurz (Member # 5396) on 10-16-2015, 08:05 PM:

If switching the lens makes a change, then it's not the motor driver/cable issue, but simply a defective lens/motor or lens motor contact.

- Carsten