Operation Theory - HP CRT Monitor s7500 Service Manual

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 NOVA NT6865 32 processor-- that has I
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
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
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4. Powerful PHILIPS TDA4863AJ A5 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 NOVA NT6865 CPU. It contains a 8051 8-bit CPU core, 512 bytes of RAM used as
working RAM and stack area, 32k bytes of MASK ROM, 10-channel 8 bit PWM D/A converter, 4-
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
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 25 and pin 26 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
by sensing the voltage through R710, R740, R741, R743, J007, J008 to pin 16 and 17 of I701.
3-3 Deflection Section
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1. I C -- autosync deflection controller is TDA4841.
2. The TDA4841 is a high performance and efficient solution for autosync monitors. All functions are
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controllable by I C bus. SDA and SCL signals coming from microprocessor feed to pin 12 and pin 13 to
control all functions.
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C BUS controlled geometric correction, contrast and
keys on front panel.
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C bus interface. When H/V sync through D-Sub signal cable enter pin
HP S7500/MV7500/CV7500
2
C Bus for auto-alignment through
& keys, they are detected
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