Philips LC4.1E Service Manual page 53

Circuit Descriptions, Abbreviation List, and IC Data Sheets
The PLL tuner UR1316 (with FM radio) delivers the IF-signal,
via audio & video SAW-filters, to the Video Signal Processor
and FLASH embedded TEXT/Control/Graphics Micro
Controller TDA120x1 (item 7011, also called Hercules). This IC
has the following functions:
• Analogue Video Processing
• Sound Demodulation
• Audio Interfaces and switching
• Volume and tone control for loudspeakers
• Reflection and delay for loudspeaker channels
• Micro Controller
• Data Capture
• Display
The Hercules has one input for the internal CVBS signal and a
video switch with 3 external CVBS inputs and a CVBS output.
All CVBS inputs can be used as Y-input for Y/C signals.
However, only 2 Y/C sources can be selected because the
circuit has 2 chroma inputs. It is possible to add an additional
CVBS(Y)/C input (CVBS/YX and CX) when the YUV interface
and the RGB/YPRPB input are not needed. One SCART-
connector is used (SCART1). This connector is fully equipped.
The video part delivers the RGB signals to the Scaler IC.
The Genesis GM5221 Scaler IC receives either the SDTV
video input signals from the Hercules or the PC input signal
from an external computer. Switching between the two signals
is done via the SD/HD selection IC (7461).
After the video processing done by the Scaler, 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.
There are two I2C 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 (this
can be traced via the fault-finding tips, or by strange
phenomena), a new panel must be ordered (see table below for
ordering codes), and after receipt, the defective panel must be
sent for repair.
Table 9-1 Ordering codes power supply
Screen size (inches)
15
20
23
9.4 Tuner and IF
On models with FM radio, 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
Ordering Code
3341 101 20021
3122 137 23101
3122 137 23071
9.4.1 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 is depending of the standard(s)
that has 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 it could be that the AGC setting
is wrong. The AGC-setting could also be mis-aligned if the
picture deforms with perfect signal; the IF-amplifier amplifies
too much.
2
C.
LC4.1E AB 9. EN 53