Picture Improvement - Philips Tda 9178; Tuner; Rgb Processor - Tda 9330 - Hitachi CL32W35TAN Serviceanleitung

PICTURE IMPROVEMENT - PHILIPS TDA 9178.

The picture improvement IC is an analogue video processor offering three main processing functions; luminance vector, colour
vector and spectral processing. Features presently being implemented are; luminance transient improvement (LTI), colour transient
improvement (CTI), variable gamma control and picture dependant non-linear Y and U, V processing by luminance histogram
analysis.
The spectral processor provides luminance transient improvement, luminance detail enhancement by smart peaking and colour step
improvement (CTI). The linewidth control may be user defined. The luminance vector processor, the transfer function is controlled in
a non-linear manor by histogram analysis of measured luminance values measured in a picture. As a result the contrast ratio of the
most important parts of the scene will be improved. A variable gamma function after the conversion offers the possibility of
alternative brightness control or factory adjustment of the picture tube.
The following functions sharpness, noise reduction and colour transient improvement (CTI) are provided by the picture improvement
IC for digital models, while 100Hz/progressive scan models provide these functions within the double scan module. All functions
2
described are switchable/adjustable via I C control using the options in the service menu.
Y, U and V signals are taken from I200 pins 49, 50 & 51 and go straight into Y U and V (pins 6, 8 and 9 of IE01). The enhanced
in in in
Y, U & V outputs originate from IE01 (pins 19, 17 & 16 respectively) and are directed to IE02 (pins 28, 27 & 26 respectively).

TUNER.

The tuner U100, is a frequency synthesis type with an unbalanced input, powered from the +5V rail while the tuning voltage is
supplied by the +33V rail, supplied from the horizontal deflection circuit. Direct frequency access, channel selection, AGC and AFC
2
functions are controlled via the I C bus. AGC, AFC and Offset controls may be selected by entering the service menu and selecting
the 'tuner' option.
Pin 1, AGC is taken from pin 62 of TDA 9320. The balanced I.F. output is taken from pins 10 & 11, which are then arrive at both the
inputs of the vision and sound SAW filters (pins 1 & 2). The outputs from X200 and X202 (pins 4 & 5 respectively) pass through to
pins 2 & 3 and pins 63 & 64 of I200, where they are demodulated.

RGB PROCESSOR - TDA 9330.

VERTICAL DEFLECTION & GEOMETRY CONTROLS.
The drive circuit for the vertical and E-W deflection circuits are generated by means of a vertical divider which gets its clock from the
line oscillator. The divider is synchronised by the incoming vertical pulse, generated by the input processor or the feature box.
The vertical drive is realised by means of a differential output current. The outputs must be DC coupled to the vertical output stage.
2
The vertical geometry can be adjusted by I C control via the service menu.
HORIZONTAL SYNCHRONISATION & DRIVE CIRCUIT.
The horizontal drive signal is obtained from an internal VCO which is running at a frequency of 13.75MHz. This oscillator is
stabilised to this frequency by means of a resonant oscillator 12 MHz. The internal VCO is synchronised to the incoming horizontal
H pulse by means of a PLL with an internal time constant. The horizontal drive signal generated by means of a second control loop
d
which compares the phase of the reference signal from the internal VCO with the flyblack pulse. The time constant loop is internal.
The I.C. has a dynamic horizontal phase correction input which can be used to compensate phase shifts which are caused by beam
current variations. Additional settings of the horizontal deflection which are realised via the second loop are the horizontal shift and
the parallelogram correction.
The horizontal drive signal is switched on and off via the so called soft-start/soft-stop procedure. This function is realised by means
of a variation to the T of the horizontal drive pulse. For EHT generators without bleeder the I.C. can be set in a fixed beam current
on
mode. In that case the picture tube capacitance is discharged with a current of about 1mA which is determined by the black current
feedback loop. With the fixed beam current option activated it is still possible to have a black screen during switch-off. This can be
realised by placing the vertical deflection in an overscan position.
An additional function of the I.C. is the low-power start-up feature. This mode is activated when a supply voltage of 5V is supplied to
the start-up pin. The required current for this function is 3mA typical. In this condition the horizontal drive signal has the normal T
off
and T grows gradually from zero to about 30% of the normal value. This results in a line frequency of about 50kHz or 25kHz. The
on
output signal remains unchanged until the mains voltage is switched-on. Then the horizontal drive signal will gradually change to the
normal frequency and duty cycle via the soft-start procedure.
The I.C. has a general purpose bus controlled DAC output with a resolution of 6 bits and with an output voltage range between 0.2
to 4V.
INPUT SIGNALS.
The RGB control circuit of the TDA 9330 contains three sets of input signals.
Y, U, V, input signals which are supplied by the input processor or feature box. The nominal input signals for u and V are 1.33 V
Peak-
and 1.05V respectively. These input signals are controlled by brightness, contrast and saturation.
to-Peak Peak-to-Peak
Two RGB sources are intended for use by the Scart, while the second is used for the OSD and teletext. The required input signal
has an amplitude of 0.7V . The switching between the internal signal and the OSD signal can be realised via a fast blanking
Peak-to-Peak
. this input is only controlled by brightness.
2
Switching between various sources can be realised via the I C bus and by fast insertion switches. The circuit contains switchable
matrix circuits for the colour difference signal so that the colour reproduction can be adapted for PAL/SCAM and NTSC.
OUTPUT AMPLIFIER.
The output signal has an amplitude of around 2V black-to-white at nominal settings. The required white point setting of the picture
tube is implemented by 3 separate gain settings for the RGB channels.
15