3M
Multimedia Projector MP8670/8745/8755/8770
Theory and Diagrams
Copyright
2000, 3M IPC. All Rights Reserved.
4-1
4.
Theory and Diagrams
To truly understand what is taking place when making advanced projector adjustments, the following
concepts must be introduced and explained. An understanding of these principles increases your
efficiency when making advanced projector adjustments.
•
Theory of Operation
•
Color Theory
•
LCD Structure Theory
•
Lamp Theory
•
Optical System Layout
4-1.
Theory of Operation
Use the MP8670/8745 circuitry diagrams as a reference for the following topics.
4-1-1.
MP8670/8745 Power Supply Circuit
When the main power switch is on and the 110V AC power is supplied, two DC power circuits are
energized. The AC power passes through a filter then on to the ballast where the AC voltage changes to
DC voltage and is split. High voltage DC current is sent to the lamp where it will have six tries to light.
Low voltage DC current is sent to the power unit circuit then to the Micro processor to power the rest of
the projector.
4-1-2.
MP8670/8745 Video Input and AD Conversion
There are two sets of video inputs. Switching between them is done using the input button on the top of
the projector or the Video1/2 button on the remote control.
Signal Board
The video signal passes though the video signal selector then to the comb filter where it is split into the
chroma signal (C) sent to the RGB/video selector and the luminal (Y) signal is sent to the sync selector.
Driver Board
The signal passes through another selector then to the AD converter. The analog signal is changed to a
digital signal and passes though the on screen display and the gate array where a smoothing affect and
resizing takes place. The digital signal is then changed back to analog and sent to the video
amplifier/inversion amplifier. The luminal signal (Y) information that passed though the gate array and
timing generator. The sampling pulse of the AD converter is generated by PLL circuit depending upon the
detection of vertical and horizontal sync. pulse. The two signals are output though the video amplifier, the
sample/hold and the video rotation, then each LCD receives the appropriate information.
There are two sets of RGB inputs. Switching between them is done using the input button on the top of the
projector or the RGB1/2 button on the remote control.
Signal Board
The RGB signal goes through a RGB1/2 signal selector then the chroma signal (C) information is sent to
the video/RGB selector and the luminal signal (Y) information is sent to sync selection.
