Philips L04A AB Скачать руководство пользователя страница 77

Страница: 77 / 90

Circuit Descriptions, List of Abbreviations, and IC Data Sheets

voltage > 3.8 V and period < 900 us. Any signal out of this
range will be considered as fault, and the chassis will be shut
down.

9.3.8

CRT panel

The RGB amplifier stage is exactly the same as in L01.1/M8.
However, the RGB amplifier IC has been changed to
TDA6107AJF or TDA6108AJF. The “A” indication is with gain
of “80” rather than “50” in L01.1/M8. The diode D6332 used in
the former chassis, to solve the bright screen during start up, is
not required because this IC has the error correction
implemented.

Scavem

In certain versions, the Scavem feature is used to enhance the
sharpness of the picture. The RGB signals are first
differentiated and subsequently amplified before feeding to an
auxiliary coil known as the SVM coil. The current, flowing
through the SVM coil during the picture intensity transients,
modulates the deflection field and thus the scan velocity.

During the first half of the intensity increase, the scan velocity
is increased (thus decreasing the current density by spreading
it on a wider area). During the second half of the intensity
increase, the scan velocity is decreased (increasing the current
density by concentrating it on a smaller area). The increasing
current density transition is sharpened. A decreasing current
density transition is processed in a similar way and is also
sharpened.

In this chassis the SCAVEM signal is different from its
predecessor because the Hercules generates the differential
SCAVEM signal inside the IC.
The supply of the SCAVEM is taken from V_bat through a 1k5
/ 5 W resistor. Compared with the L01.1/M8, this has the
advantage of getting better performance for the pattern with
tremendous SCAVEM current (like V_sweep). In this former
chassis, because the supply was taken from the 200 V through
a 8k2 / 5 W resistor, the supply dropped significantly during a
large SCAVEM current. In this chassis, the drop due to the
pattern will be less because of the lower supply voltage
impedance.
In the Main Board, 1st stage amplification is taken care by 7208
with the pull up resistors (3361, 3387) located in the CRT panel.

TS7361 and TS7362 is the current buffer delivering the current
to the output stage. The diode D6361 is to lightly bias these
transistors, to get rid of the zero crossover of the stage.
After that, the signal is ac-coupled to TS7363 and TS7364
where the emitter resistors (R3364 and R3370) will determine
the final SCAVEM current. TS7363 and TS7364 are biased by
R3363, R3366, R3367 and R3368.
C2387, R3388, R3389, R3365, R3369, C2384, and C2385 are
used for suppressing unwanted oscillations.
The function of TS7376 is to limit the SCAVEM current from
going too high. It basically senses the voltage after R3373 and
clamps the SCAVEM signal through D6367 and C2376.

9.3.9

2fh synchronisation

The 2fh sync generation is done by the DPTV SVP (IC7201).
This IC converts the H and V sync signals (Hs and VS) coming
from the UOC into 2fh sync signals (HSYNC and VSYNC)
which are outputted to the TDA9332 (HOP).
The HOP again generates the necesarry deflection signals like
VD+ and VD- for the Frame deflection; HD for Line deflection;
EW_DRIVE.

9.4

Control

The Micro Controller is integrated in the UOC (Hercules). For
dynamic data storage, such as SMART PICTURE and SMART
SOUND settings, an external NVM IC is being used.
Another feature includes an optional Teletext/Closed Caption
decoder with the possibility of different page storage depending
on the Hercules type number.

9.4.1

Block Diagram

The block diagram of the Micro Controller application is shown
below.

Figure 9-5 Micro Controller block diagram

9.4.2

Basic Specification

The Micro Controller operates at the following supply voltages:
•

+3.3 V_dc at pins 33, 125, and 19.

•

+1.8 V_dc at pins 126, 36, and 33.

•

I2C pull up supply: +3.3V_dc.