Philips LC4.5E Service Manual page 63

Circuit Descriptions, Abbreviation List, and IC Data Sheets
The video part delivers the RGB signals to the Scaler IC.
The Genesis GM1501 Malibu Scaler IC can receive two video
input signals: SDTV (from the Hercules), DVI (from an external
DVI source), or PC (from an external computer).
After the video processing, the digital data is sent via a Low
Voltage Differential Signalling bus to the LCD panel. LVDS is
used to improve data speed and to reduce EMI significantly.
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There are two I C lines and two interrupt and communication
lines (TV_IRQ and TV_SC_COM) for the Scaler control. The
Scaler communicates with the Hercules as a slave device. To
avoid buffer overflow at the Scaler side, the TV_SC_COM line
provides the necessary hardware flow control. To allow bi-
directional communication, the Scaler can initiate a service
interrupt-request to the Hercules via the TV_IRQ line.
The Hercules and EEPROM are supplied with 3.3 V, which is
also present during STANDBY.
The EEPROM, or NVM (Non Volatile Memory), is used to store
the settings.
The sound part is built up around the Hercules. The Source
Selection, Decoding and Processing are all done by the
Hercules.
Power supply input are several DC voltages coming from a
supply panel.
9.3 Power Supply
For Service, this supply panel is a black box. When defect a
new panel must be ordered.
9.4 Input/Output
The I/O is divided over two parts: Rear I/O and Side I/O. The
rear has two SCART inputs, a PC (VGA) input, a DVI input, and
an Audio input. The side has a CVBS and Y/C (SVHS) input.
EXT1: The input of SCART1 is CVBS + RGB + L/R and the
output is the video (+ sound) signal from the tuner
(SC1_CVBS_RF_OUT).
EXT2: The input of SCART2 is Y/C + CVBS + L/R. The output
signal is CVBS_SC2_MON_OUT (+ sound).
SCART2 is meant for VCR and has therefore some additional
signals in relation to EXT1 but no RGB: it has the possibility for
Y/C_in: Y_in on pin 20 and Chroma_in on pin 15.
The selection of the external I/O's is controlled by the Hercules.
PC (VGA) in: This input is directly going to the Scaler IC. See
paragraph "Video: Scaler Part".
9.5 Tuner and IF
A Philips UR13xx Tuner with second input (for FM Radio) is
used in the TV board. The SIF and FM signals are decoded by
the Hercules. Tuning is done via I
9.5.1 Video IF Amplifier
The IF-filter is integrated in a SAW (Surface Acoustic Wave)
filter. One for filtering IF-video (1328) and one for IF-audio
(1330). The type of these filters depends on the standard(s)
that has/have to be received.
The output of the tuner is controlled via an IF-amplifier with
AGC-control. This is a voltage feedback from pin 31 of the
Hercules to pin 1 of the tuner. The AGC-detector operates on
top sync and top white level. AGC take-over point is adjusted
via the service alignment mode "Tuner" -"'AGC". If there is too
much noise in the picture, then possibly the AGC setting is
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C.
LC4.5E AA
wrong. The AGC-setting could also be mis-aligned if the picture
deforms with perfect signal. In that case, the IF-amplifier
amplifies too much, resulting in a distorted video-signal.
9. EN 63