Ic Functions; Vpc 3230; Video Processor - Loewe Q2500B Serviceanleitung

Technology of Q 2500 colour TV set
100 Hz principle
Half .
pic. A
Half .
Half
pic. B
picture
memory,
50Hz
3.5 Mbit
Sampling rate
13.5 MHz
In the Y signal path there is a peaking circuit.
It is used to produce black/white edges on
overshoots, which increases the sharpness of
the picture. The height of the overshoot can
be adjusted with the "Sharpness" operating
function.
With three output side DACs analogue Y-, R-
Y- and B-Y- signals are produced, which are
then output on pins 44, 46 and 48.
Finally the Y- and colour difference signals are
fed through low-pass filters to filter out inter-
ference pulses and the residue of digitisation.
The last IC is the TDA 9332 for the 100 Hz
colour signal processing. It controls the RGB
power output stages to the c.r.t plate.
The Y-, R-Y- and B-Y signals output on pins
26, 27 and 28 produce RGB signals using
analogue matrix circuits.
The IC carries out further processing of ana-
logue RGB signals (twice), CCU signals
(once) and signals from the optional VGA in-
terface or online module. Depending on the
associated blank information, both the inter-
nally produced and the two RGB signals from
a selection circuit are switched.
Document Q 2500
Half . .
Half
Half
pic. A . pic. B Half .
pic. A
pic. B
100Hz
Sampling rate 27 MHz
The following integrated modules are respon-
sible for colour saturation, brightness and con-
trast setting. Control is via the I²C bus from
the CCU. The same is true for the white and
black value setting. An automatic black value
setting is also available. With this cutoff con-
trol, signs of ageing, e.g. the c.r.t, are cor-
rected (see description of the RGB output
stages).
The signals reach pins 40, 41 and 42 via the
RGB output amplifier and are held there at 4
Vss for control of the speed modulator and the
RGB output stages.

4.2.15 IC functions

The following paragraphs give a more detailed
description of the functions of the ICs used for
picture processing.
In the descriptions, the processes are shown
in a much-simplified form. The operations
necessary for the execution of the functions
are inevitably much more complex.

4.3 VPC 3230

Video processor

The VPC 3230 is a recently developed video
processor from Intermetall in 0.8 µ CMOS-
technology. The functions are contained in an
80 pin PLCC housing.
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