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How to change lens on NEC MT850 projector


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We have a NEC MT850 in excellent working order, but now want to swap the 112mm lens back to the original.  This is not a quick-change, user-friendly option, but must involve getting into the projector, which is not an obvious process.  Does anyone have any guidance, or know of any firms in the Manchester/W Yorkshire area who might have the back knowledge of how to do this, please?

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Buhl Series 771 Lenses for NEC Projector Models MT850, MT1050 and MT1055

1) Disconnect unit from power source. Remove the fan cover to the rear of the input panel on the left side of the projector and remove one small Philips head screw. Turn the projector up-side-down and remove four screws, each down a hole clearly visible on the underside of the projector. Remove two screws on the underside of the front cover. Turn projector back right-side-up and gently lift the top cover from the rear of the projector. The top and front covers may come off as one or they may come off separately. Note the wires that run from the front cover to the inside of the projector. Unplug these wires from where they connect on the inside. Set the top and front covers aside.

2) There are four screws, one at each corner of the metal sheet covering the top circuit board. Remove these four screws and set the metal sheet aside. There are two screws at the very back of the exposed circuit board, one right near the rear speaker and one slightly inward from that (it is not necessary to remove the two screws near the PC card slot). Disconnect the two ribbon connectors immediately in front of the PC card slot and gently lift the circuit board up and out of your way (note where the circuit board snaps into a connector near the input panel). 

3) Remove the four screws that hold the prime lens in place. The lens should lift out of the projector freely. Set the lens aside.

4) Place your Buhl lens in the cradle and secure with the same four screws. 

5) When replacing the top circuit board, ensure that it properly snaps into the connector up by the input panel. Replace the two screws at the rear of the circuit board, then replace the metal sheet. Reconnect the ribbon connectors along the side, then reconnect the wires from the front face cover to the underside of the circuit board. Gently replace the top and front covers and replace all the screws. Replace the fan cover.

**IMPORTANT** Be certain to replace all the screws that secure the top circuit board in place BEFORE powering up your projector. Failure to do so could damage the projector! 

6) To focus the lens, grab the outermost portion of it and turn it left or right. If you have a zoom lens, rotate the raised ring located toward the front of the lens to zoom.


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