Vibrant VM77S, Service Manual

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VM77S
Operation Theory Page 9
3 Operation Theory
This is a fully digital controlled multi-sync color monitor that is compliant with DDC1 and 2B Plug and Play
VESA standard and offers the following main features.
3-1 Main Features
1. Simplified design with minimum components.
2. The MYSON MTV212 M(A) 32 processor-- that has I
2
C BUS controlled geometric correction, contrast
and brightness-- offers the functions for: (a) Contrast, (b) Brightness, (c) H-size, (d) H-position, (e) V-
size, (f) V-position, (g) Pincushion, and (h) Trapezoid.
In addition, it also offers more functions as: (a) Sync. processor, I/P and O/P, (b) Mute, (c) Power saving
- Suspend & Stand-By, (d) Power saving override, (e) DDC1/2B, (f) I
2
C Bus for auto-alignment through
signal cable (g) CS1/CS2/CS3/CS4 for linearity and size compensation.
3. Stores up to 10 factory preset modes and offers 8 user modes. There are 16 function icons at OSD. They
are controlled by
1 2
keys on front panel.
4. Powerful PHILIPS TDA4863 and TDA4841 present the following useful functions: (a) Pincushion, (b)
Trapezoid, (c) V-Position, (d) V-Size, (e) Vertical’s “C” and “S” correction -- factory adjust, (f) Pincushion’s
V. position correction, (g) Corner correction -- factory adjust, (h) Pincushion unbalance correction --
factory adjust, (i) Parallelogram distortion -- factory adjust, (j) Moire cancellation, (k) X-ray protection,
and (l) Full horizontal and vertical auto sync capability.
5. Software controlled auto shut off function activated if fH < = 29 kHz and fH > = 70 kHz.
6. Full range AC input and simplified line filter design.
3-2 Microcontrol Section
1. This monitor uses MYSON MTV212 M(A) 32 CPU. It contains a 8051 8-bit CPU core, 256 bytes of
RAM used as working RAM and stack area, 32k bytes of OTP ROM, 13-channel 8 bit PWM D/A
converter, 2-channel A/D converters for key detection saving I/O pins, internal H. sync and V. sync
signals processor providing mode detection, and an I
2
C bus interface. When H/V sync through D-Sub
signal cable enter pin 41 and pin 42, the CPU performs frequency / polarity detection and calculate and
send to H/V sync OUT. Then CPU reads the data from I703 and transfer to device 4841 and some DAC
in CPU, above operation takes about 500 ms.
2. There allowed 8 factory preset modes and 8 user modes. There are 11 functions, Contrast, Brightness, H.
Size, H. Position, V. Size, V. Position, Pincushion, and Trapezoid, Rotation, H. Moire, V Moire, all controlled
by OSD icon which can be adjusted by user.
3. The pin 27 and pin 28 are used for ATE function. When CPU receives C6 as slave address, it will operate
in ATE mode which is used for auto-alignment. After alignment the data will be stored in I703.
4. The user control parameters are selected by OSD icons, through
1
&
2
keys, they are detected
by sensing the voltage through R710, R740, R741, R743, R716, R717 to pin 25 and 26 of I701.
3-3 Deflection Section
1. I
2
C -- autosync deflection controller is TDA4841.
2. The TDA4841 is a high performance and efficient solution for autosync monitors. All functions are
controllable by I
2
C bus. SDA and SCL signals coming from microprocessor feed to pin 19 and pin 18 to
control all functions.