IBM 9493-AG1, Service Manual

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DESCRIPTION OF BLOCK DIAGRAM
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1. Video Amp & PLL & A/D Converter Circuit
AD9884(U5) is one chip IC which it supports three function block of Video Amp, PLL and A/D converter.
Video signal (0.7Vp.p) clamped through C63, 64, 65 inputs to U5’s R, G, and B pins. The signal level is 0.7Vac added
4Vdc. This signal is processed as a proper 8 bit digital signal for input of MX88L281 (U1) by U5’s amplifying, phase
locking, and A/D converting operation.
U5 generates clock and horizontal sync for MX88L281 (U1) with MC14066B(U11)’s output horizontal sync signal.
Sync Process (U14)’s clamp output makes U5 keep video signal’s voltage from zero to AC signal’s minimum level
constantly regardless of various input video signals.
2. Macronix Circuit (Scaler chip)
The MX88L281 (U1) gets the video signal converted analog to digital from U18, and carries out four function of image
processing that interpolates input signal less than 1024x768 resolution to that of 1024x768 resolution, displays one to
one image without interpolation, mixes OSD(On Screen Display) signal by interfacing with OSD IC (U2), and controls
three memories(U6, 7, 8) as frame converter.
U1 outputs signals of HSYNC-OUT, VSYNC-OUT, DEN, CLKA-ODD, and each 8 bit R, G, B to transmitter IC (U16).
3. Memory Circuit
2M byte SDRAM(U6, 7 , 8) is used as a frame converter for supporting up to 85 Hz frame rate and controlled by
MX88L281(U1).
The control signals are CKA, CLK, UDOM, LDOM, /WE, /CAS, /RAS, /CS, /BA.
4. Panel-Link Circuit
Panel link transmitter (U16) delivers digital signal to the receiver inside LCD module by method of abstraction.
The abstracted signals are pairs of TX0+-, TX1+-, TX2+-, TXC+- of which voltage swing is 0.5V each.
Its swing is similar to LVDS (Low Voltage Differential Signal).
Transmitter (U16) gets signals of HSYNC-OUT, VSYNC-OUT, DEN, CLKA-ODD from U4, and outputs LVDS
through TX pin. When PD pin’s input is low, transmitter goes to power down mode.
5. System Controller (Microprocessor) Circuit
1) Microprocessor (U4) distinguishes polarity and frequency by calculating horizontal and vertical sync input from
signal source.
2) Microprocessor (U4) carries out power control by sending power-down trigger signal to each IC.
U1, U5, and U16 has PD(Power-down) pin which operates at active-low each.
3) Microprocessor (U4) communicates with EEPROM (U10), AD9884 (U5), MX88L281 (U1), and OSD IC (U2)
through SCL and SDA or 8 bit bus line. It makes all devices with communication channel operated properly.
4) Microprocessor (U4) let User adjust screen by each OSD function.
6. DC/ DC Converter
This circuit supplies DC power for each device needing DC voltage of 3.3VD, 3.3VD1, 3.3VA, PVD_ADC, 5VA and
5VSTD.
LM2674(U13)and LM2596(U15) , the DC/DC controller IC converts input 24Vdc into each voltage to be needed with
peripheral circuit composed of Choke Coil (L8, 9), condensing components (ZD5, ZD6) and Regulators
(U22, 19, 20,2 3, 24).
5VSTD is supplied for Microprocessor through regulators (U22).
MODPWR for LCD module power are supplied by switching FET(U12) and regulator(U16), controlled by
Microprocessor’s triggering signal (M-PWR ON).