The PANASONIC CHASSIS Z8 is the first type using the PHILIPS UOC (Ultimate One Chip) for the development and a ITT-Micronas MSP processor in sound sections.
The chassis is a 2 chip development therefore is higly integrated.
The technology used in this set is featuring the first PANASONIC with PHILIPS UOC BASED CHASSIS development, The Ultimate One Chip Television provides manufacturers with a single chip, global TV concept with a wide range of options using advanced proven technologies for both mixed-signal and digital processes.
By integrating the core functions of picture and sound decoding, digital processing and teletext and on-screen display into a single package, the Ultimate One Chip Television reduces the number of peripheral devices required. It allows the manufacturer to design a single chassis for a world family of television receivers. The same chassis can be used for different size tubes, for single and multiple transmission standard receivers (PAL/NTSC/SECAM), and can provide a range of facilities including stereo sound and different teletext standards.
The analog circuitry, built in Philips' BiMOS process technology, is primarily concerned with the colour decoding and other picture and sound processing. The digital circuitry, built with Philips' CMOS technology, looks after on screen display using a microprocessor core and specialist caption decoder and teletext circuitry. Also included as part of the digital circuitry is one time programmable (OTP) memory and up to 2K RAM. The process technologies are both regarded as amongst the most advanced in the industry, providing higher levels of integration and lower levels of power consumption than competitive processes.
The Ultimate One Chip Television requires lower power at start up, for operation and for standby, than other solutions currently available, providing the opportunity for 'green' sets. The TV signal processor includes a single, automatic search, PAL/NTSC or multi-standard decoder, with a multi-standard IF circuit incorporating an alignment free PLL (Phase Loop Lock) demodulator. Other features include multi-standard FM sound, with a choice of mono or stereo, an audio switch, which removes the need for separate external band-pass filters, and an automatic volume levelling circuit. The design was carried out initially at two of Philips Semiconductors design centres, with Southampton, UK, carrying out digital design and software development and Nijmegen, Netherlands responsible for analog design. The design team in Taiwan has since become involved in tailoring the design for specific applications. (CHASSIS Z8).
Even by his grade of integration is slighlty complex.
It was reliable except for the classic rate of dry joint and a HOT running Frame deflection output IC Which sometimes was failing and it was in some cases a really powerful CRT TUBE NECK CUTTER ! ! ! !!!!!!!!!!
PANASONIC TX-25CK1C/M CHASSIS Z8 BACKGROUND OF THE INVENTION1. Field of Invention
The present invention relates to television technology, and more particularly to providing television functionality on a single integrated circuit chip.
Television systems have become increasingly complex as consumers continue to demand greater functionality and performance from television sets. Furthermore, the miniaturization of television systems demands that while complexity is increasing, that the size of electronic circuitry to support this complexity and performance must be reduced. At the same time, market forces continue to drive prices lower for television sets. Current electronic circuitry to support the functionality needed to receive audio and video signals that are either analog or digital and process those signals to provide a signal suitable for display on a television often consist of several integrated circuits. Furthermore, additional functionality related to value added features, such as teletext or e-commerce often requires additional integrated circuits.
What is needed is a system for providing television functionality and ancillary functionality on a single integrated chip to reduce costs and support the continued miniaturization of electronics for televisions.
The present invention addresses the conflicting consumer demands of television system miniaturization and reducing the cost of televisions.
PANASONIC Z8 Chassis Circuit Explanations / functions and features:
PANASONIC TX-25CK1C/M CHASSIS Z8 Power Supply
Themains ACvoltage used for Z8 is fed via connector
E2 situated on the E-Board. From the connector E2
the mains AC power supply is fed via the main TV
On/Off switch S801 and line suppression filter L801
before being fed to the standby transformer T801.
At the standby transformer T801 the AC supply splits
into two paths.
The first path sees the AC supply being fed to the
normally open contact of the standby relay RL801.
The second path has the AC supply being fed via the
windings P2/P1 of the standby transformer T801.
3.1. Standby Power Supply Circuit
The standby transformer T801 has the AC supply as
just mentioned being fed via the primary winding
The output of the secondary windings S2/S1 of the
standby transformer is fed to the bridge rectifier
D1201, where the AC voltage is full rectified. Here the
supply takes two paths.
The first path provides smoothing to the supply via
capacitor C1201 before being fed to IC1202 pin 1.
The output at pin 3 is smoothed further by capacitor
C1203, and the 5V standby supply output is fed to the
EEPROM IC1103, the remote control receiver
IC1104 and the Q-Link circuit. The 5V standby supply
is also fed to IC1201, where the output at pin 3 is
smoothed via C1204, to provide 3.3V standby supply
to the Ultimate One Chip (UOC) IC IC601 pin 61, and
the reset IC IC1102. This 3.3V is also used to bias the
standby relay control transistor Q1204.
The second path from the bridge rectifier sees the
supply voltage being fed via resistor R1202 to the
standby relay RL801 and the relay winding to the
collector of transistor Q1201. Transistor Q1201,
which is controlled by Q1204, is responsible for
switching the TV in and out of standby, under the
control of the UOC IC IC601 pin 1.
The two supplies mentioned allow the circuits to
operate during standby, which is required to process
the switch ON command from the remote control or
local keys, allowing the TV to be switched out of
To reduce the load on the standby transformer T801,
a 10V supply is fed from transformer T552 pin 6 via
rectifying diode D554, R1209 and D1205, to pin 1 of
3.2. Power Supply Circuit
The STR-F6523, IC801 is used in the Z8 power
supply to control and regulate the power supply
operation. This device features over-voltage
protection and thermal shutdown. The output stage of
the IC incorporates a built-in MOSFET switching
The supply voltage for the main power supply circuit
is fed via the standby relay RL801 to the bridge
rectifier D802 where the AC voltage is fully rectified
and smoothed by capacitor C809.
This smoothed DC voltage of approximately 300V
then feeds the supply to pin 3 of the switched mode
power supply IC IC801, where the DC voltage is held
at the drain of the internal MOSFET, by its parallel
3.4. Start Up
A start-up circuit is used to start and stop the
operations of the control IC IC801 (STR-F6523), by
detecting the voltage appearing at the VIN terminal,
At start-up, capacitor C810 is charged via R804,
which causes the voltage at pin 4 of IC801 to
increase. Once VIN terminal pin 4 voltage reaches
approximately 16V, IC801 begins to operate anddrive
the internal power MOSFET, causing current to flow
through the drain/source terminals at pins 3 and 2,
and to the winding B1-B2 of switching transformer
T802 via L803 and R809. The current at terminal B1
is split into two paths.
The first path follows the current being fed to the
winding B1-B2 and back to pin 4 of IC801 via R811
and D805. Once the control circuit starts operation,
the voltage at the VIN terminal pin 4 of IC801 starts to
decrease. However, the drive winding voltage
reaches the set value before pin 4 voltage drops to the
shutdown voltage of 10V. Hence the voltage supply to
pin 4 is maintained.
The second path is connected from terminal B1 to P2
of the FBT. This causes current to flow via the winding
P2-P1, which provides the +B supply to the FBT T552
3.5. Oscillator and Constant Voltage
The oscillator within IC801makes use of the charging
and discharging of internal capacitor C1 (4700pF)
and generates pulse signals which turn the internal
power MOSFET On and Off. The constant voltage
control of a switch mode power supply is performed
by fixing theOFF time of theMOSFET (around 50uS)
and changing the ON time in the pulse width control
3.5.1. ’ON’ Condition and Time
When the switching power MOSFET is ON, C1
begins to charge.
3.5.2. From ’ON’ to ’OFF’
When the voltage on C1 reaches (approx.) 6.5V, the
output from the oscillator is reversed, and the internal
switching power MOSFET switches OFF.
3.5.3. ’OFF’ Condition and Time
With the power MOSFET now OFF, Capacitor C1
starts discharging through R1, at the fixed time
determined by the time constant C1, R1.
3.5.4. From ’OFF’ to ’ON’
When C1 voltage has dropped to around 3.7V, the
output from the oscillator is reversed again and the
power MOSFET again turns ON, thus repeating the
The power supply ON time is changed by controlling
the the charge current of the internal capacitor C1.
D804 is a photocoupler, which provides the drive
current to the ’FB’ (Feedback) terminal of IC801 pin
1 via D812 and R806. The photocoupler current
varies in response to the output from pin 2 of
comparator IC IC802.
IC802 pin 1 monitors the +B supply voltage via the
zener diode D814 by comparing it with a reference
voltage established internally within IC802.
If the AC mains input voltage to the switched mode
power supply increases, the +B voltage level tends to
rise. This results in an increased current flow to theFB
terminal, pin 1 of IC801 via the photocoupler D804,
diode D812 and resistor R806. Increasing the rate at
which C1 charges, causes the power MOSFET ON
time to reduce. This in turn causes the +B level to
return to its nominal value.
3.7. Drive Circuit
The drive circuit charges and discharges the
capacitance between the gate and the source
terminals of the internal powerMOSFET, by receiving
pulses from the oscillator. The basic circuit
configuration is a totem-pole type connection of
transistors. Since the maximum sink current (0.3A)
can become active even when theVIN voltage is lower
than the shutdown voltage, the drive circuit turns off
the MOSFET without fail.
3.8. Protection Circuitry
3.8.1. Over-voltage Protection (OVP)
Over-voltageProtection is used to protect IC801 ifVIN
pin 4 terminal rises to approximately 22V. Although it
basically functions as protection for pin 4 against
overvoltage, it is also used to protect against
overvoltage of the secondary output (in the event of
failure of the regulation, for example). This is because
pin 4 is supplied by winding B1-B2 of transformer
T802, this voltage being proportional to the output
voltage of the secondary side.
3.8.2. Over-current Protection (OCP)
Overcurrent Protection is performed pulse-by-pulse
by directly detecting the drain current of the internal
power MOSFET. Since the detection voltage is
monitored by an internal comparator of IC801,
constant temperature stabilisation is also achieved.
The Drain-Source current through the power
switching MOSFET is passed via the resistor R809,
which develops a voltage across it. The input voltage
to IC801 pin 1 (OCP/FB) is passed to an internal
comparator. When this input voltage exceeds a
pre-determined value, the drive output is pulledLOW,
resulting in the power MOSFET switching OFF.
The latch circuit is used to pull the output of the
oscillator LOW (switching MOSFET OFF) when the
over-voltage protection or thermal shutdown circuits
In this condition the VIN terminal pin 4 decreases until
the shutdown voltage of 10V is reached. At this point
pin 4 begins to rise again but when it reaches the start
up level of 16V, the latch circuit continues to stop the
When the latch is on, VIN voltage at pin 4 increases
and decreases within the range 10V to 16V, as shown
in the above diagram, and is prevented from rising
Cancellation of the latch circuit operation is achieved
by restarting the AC input to the circuit after switching
off the TV.
3.8.4. Thermal Shutdown
This circuit triggers the latch when the body
temperature of the IC exceeds 140EC. The
temperature is sensed by the control IC, but also
works against overheating of the MOSFET, as both
are mounted on the same lead frame.
3.9. Secondary Supplies
On the secondary side, the transformer T802
supplies the following voltages:
+12V to supply the horizontal driver stage.
+20V to supply the East/West correction IC
+27V to supply the audio output IC IC251.
3.9.1. +12V Supply
The signal from pin 16 of T802 is rectified by diode
D851 and smoothed by capacitor C856. The 12V
supply voltage is then applied to the horizontal driver
transformer T553 via diode D501 and resistor R503.
During start-up, the 12V supply feeds the horizontal
stage asmentioned. However, when the whole power
supply is up and running normally, the supply voltage
fromthe secondary of T802 is no longer required. The
horizontal stage now takes its 12V supply from the
FBT T552. This is required to reduce the load on the
secondary and provide drive current to the horizontal
driver transformer T553.
3.9.2. +20V Supply
The signal from pin 14 of T802 is rectified by diode
D853 and applied to the series regulator IC702 to
supply +20V to the East/West circuit (model
3.9.3. +27V Supply
The signal from pin 14 of T802 is rectified by diode
D853 and applied to the emitter terminals of
transistors Q851 and via resistor R855 to Q852. This
voltage to Q852 is fed via the emitter/collector
junction. At the same time, the signal from pin 13 of
T802 is rectified by diode D852 to provide a voltage
of +27V, which is fed to the audio output IC IC251.
This supply voltage of +27V however is too large for
the abovementioned ICs when under load and so the
supply voltage has to be reduced. As the load on the
above ICs increases, the voltage drop across R856
increases causing the base of Q851 to becomemore
negative with respect to its emitter. With Q851
conducting the base bias of Q852 becomes more
positive with respect to its emitter, thus causing the
supply voltage to the ICs to be reduced.
However by reducing the supply voltage to IC251, the
output power is also reduced. This is compensated
for by the increased current flow via R853/ R854. This
in turn ensures that the output power of the ICs is not
3.10. Voltage Supplies
3.10.1. +12V Supply
The +12V supply is output from transformer T552 pin
4 and is rectified by diode D553. This rectified voltage
is smoothed by capacitor C566 before being fed to the
vertical output IC IC451 pin 6. The +12V supply also
feeds the horizontal driver transformer T553 via diode
D510 and resistor R503.
3.10.2. -12V Supply
The -12V supply is output from transformer T552 pin
5 and is rectified by diode D559. This negative voltage
is smoothed by capacitor C564 before being fed to the
ground terminal pin 1 of the vertical output IC IC451.
3.10.3. +10V Supply
A supply of approximately 10V is output from
transformer T552 pin 6, and fed to diode D554. This
rectified voltage signal is then smoothed by capacitor
C554 before being fed to the series regulator IC852
and the standby voltage regulator IC1202.
3.10.4. +8V Supply
The 8V supply is derived from the 10V supply line
which is fed to the series regulator IC852 pin 1. The
output of IC852 pin 3, smoothed by capacitor C857,
is used to supply 8V to the TV control processor IC
IC601, RGB output stage (Y-Board) via connectors
E8 and Y2 pin 6, sound processor IC2001 and
SECAM IF audio switching IC IC201 (Frenchmodels
only). IC852 also supplies the 5V series regulator IC
3.10.5. +5V Supply
The 5V supply is derived from the 8V supply line
which is fed to IC851 pin 1. The output at pin 3,
smoothed by capacitor C851, is used to supply 5V to
the tuner, reset IC IC1105 and the sound processor
IC2001 (model dependant).
PANASONIC TX-25CK1C/M CHASSIS Z8 TV Signal, Control and Teletext Processing
The TDA9350/60/80 series IC601 used on Z8
chassis, is a one chip solution in TV processing. The
Philips Ultimate One Chip (UOC) IC combines the
functions of a TV signal processor and teletext
decoder as well as an embedded microcontroller
used to perform control processing. The TV signal
and teletext processing stages will be looked at later.
First, the control processing stage of the UOC IC will
Control Processing Stage
The elements that theUOCIC required to performthe
control functions are:
12MHz internal clock
32 - 128K x 8 bit late programmed ROM
3 - 12K x 8 bit Auxiliary RAM
Interrupt controller for individual enable/disable
Two 16 bit Timer/Counter registers
IDLE and Power Down (PD) mode
14 bits Pulse Width Modulation for Voltage
8 bit A/D Converter
Programmable as general I/O, ADC input or
PWM (6-bit) output
4.1.1. Input Control
Pin 6 - Keyscan
The local commands are fed to the UOC IC IC601 as
serial data. This data is input via pin 6. This pin is held
at 3.3V due to the pull-up resistor R1140, which is
connected to the 3.3V standby supply. This means
that the High level is also maintained during standby
condition. Operating commands fed from the local
keys results in varying voltages being applied to pin
6, which in turn initiates the various controls.
When operating commands are fed via the remote
control to pin 64 of IC601, pin 6 of IC601 also outputs
a pulse, which feeds transistors Q1102 and Q1107 to
provide a flashing standby LED D1104.
Operating commands issued from the local and
remote control are treated with equal status.
Pin 8 - Slow Switching
The circuit is designed so that it is possible to switch
over to AV operation from all programme locations to
the AV interface. The AV 21 pin scart socket JK3102
allows composite video and RGB signal input. Slow
switching being provided via pin 8 for composite video
Pin 36 - EHT / Short Circuit Protection
This input to the UOC IC which is normally biased by
R2202 and R621, provides protection by switching
the TV into standby mode.
Short circuit protection is provided via transistor
Q603. The supply lines which are monitored are:
+200V supply monitored by D603.
A voltage drop in the +200V supply causes the
voltage across resistor R631 to decrease. This in
turn causes diode D603 to conduct. The base of
Q603 is held high by resistor R622. The voltage
drop applied to the base of transistor Q603,
causes Q603 to switch On. The protection input
at pin 36 of IC601 is now pulled High, switching
the TV into standby.
+5V supply monitored by D601.
A drop in the +5V supply is applied to the base
of transistor Q603, causing the transistor to
switchOn. The protection input at pin 36 of IC601
is pulled High, switching the TV into standby.
In addition to the supplies mentioned above,
protection is provided for the +8V supply, which is
carried out internally within the UOC IC via pins 14
and 39. When the voltage drops below the
pre-determined reference, the TV is switched into
Protection is also provided for the Automatic Beam
current Limiting (ABL) circuit via D403, discussed in
Pin 49 - Automatic Beam Current Limiting
Beam Current Limiting is performed internally within
the UOC IC IC601, and is used tomonitor the voltage
at the BCL terminal pin 49. The brightness and
contrast varies in response to the voltage at pin 49 of
The control paths to the BCL input pin 49 is discussed
in the CATS Eye control section 4.1.2. and Colour
Output section 9.1.3.
Pins 58 / 59 - XTALIN / XTALOUT
The internal oscillator of the UOC IC is synchronised
with an external 12MHz quartz crystal X601 which is
connected to pins 58 and 59.
The clock frequencies for the I2C bus systemare also
obtained from this frequency by internal dividing.
The same 12MHz clock signal is also divided down
and used to synchronise the video processing stage.
Pin 60 - Reset
During power On/Off operation, or during a fall in
voltage to the UOCIC, incorrect operationmay occur.
To prevent this incorrect operation, the UOC IC has
a reset signal input via pin 60.
The reset signal is provided by reset IC IC1102 pin 1,
which keeps theUOC IC in a stable condition until the
voltage level has risen and become stabilised. This
reset IC IC1102 which is fed a 3.3V standby supply,
is input via pin 2.
Pin 64 - Remote IN
The commands required for control of the TV receiver
are applied from the remote control.
The command from the remote control transmitter is
applied via IC1104, RPM-637BRS remote control
receiver to pin 64 of the UOC IC. This command data
is received in serial format.
4.1.2. Output Control
Pin 1 - Standby
This output port of the UOC IC is used to control the
switching of the TV in and out of standby. The signal
path from this output at pin 1 follows two paths.
The first path is fed via the controlling transistor
Q1204. A High level is applied from pin 1 to the base
of transistor Q1204, causing Q1204 to switch On.
This in turn causes Q1201 to switch Off, preventing
current flow via the winding of the standby relay
RL801. This results in the mains AC supply being
removed from the power supply circuit.
Likewise when a low level is fed to the base ofQ1204,
the transistor is biased Off, thus allowing transistor
Q1201 to conduct by a High level which is applied via
R1205. When Q1201 conducts, current via the
standby relay causes the relay contact to close and
feed the mains AC voltage to the power circuit.
The second path is fed via resistor R1141 to the
collector of transistor Q1109. During standby, the
High level applied from pin 1 to collector Q1109
causes Q1107 to conduct, switching the LED D1104
When an operating command is used either from the
local keys or remote control, the keyscan output pin
6 of IC601 is pulled Low, causing transistor Q1102 to
switchOff. This results in the base of transistorQ1109
to go High due to pull up resistor R1146, to switch
Q1109 On. Q1110 also conducts pulling the base of
Q1107 Low, thus switching it Off. This results in the
standby LED D1104 switching Off.
Pin 4 - L/L’
Pin 4 of the UOC IC IC601 is used to select between
the two types of SECAM standards L/L’. This control
signal is used on SECAM L models only.
Pin 5 - CATS Eye
Pin 5 of theUOC IC is used to control a feature known
as CATS (Contrast Automatic Tracking System).
This is used to adjust the contrast level depending on
the external light surrounding the TV. The level of the
adjustment made is dependant upon the mode
selected via the OSD (Medium / Maximum).
The light sensed by the LDR (Light Dependant
Resistor) R1283 is used to control the conduction of
transistor Q1101 which in turn, controls the voltage
level at pin 49 of IC601 and thus, the contrast level.
Pin 7 - Neg / Pos
This output control is used to select between
PAL/NTSC (Negative modulation) and SECAM
(Positive modulation) standards selection.
Pin 7 is also used as an input on UK models only, to
achieve the highest possible signal from the tuner via
Pin 11 - Mute
Themute control which is output from the UOC IC pin
11 is fed to the audio output IC IC251 pin 3 via Q255.
Pin 11 of IC601 which is pulled Low for normal
operation, is biased by resistor R1141 to the 5V
During channel change, tuning and muting
operations, the Low level output from pin 11 is
disabled causing the base of Q255 to go High,
switching it On. This results in pin 3 of IC251 being
pulled Low, resulting in the audio output beingmuted.
Muting is also provided for audio POP during On/Off
operation via transistor Q253,
Pin 62 - Q-Link_In / Pin 63 - Q-Link_Out
Q-Link input and output is a model dependant
function used to control the transfer of information
and user functions to and from the TV / VCR via AV
21 pin socket JK3102.
The AV link control line fed from pin 10 of the 21 pin
AV socket is fed to the Q-Link circuit made up of
Q1103, Q1106, Q1105 and Q1104.
Where data is fed from the TV to the VCR, theQ-Link
output terminal pin 63 of the UOC IC IC601 is used.
This results in the data being fed from pin 63 of the
UOC IC IC601 via Q1106.
Where data is input from the VCR to the TV, then the
Q-Link In terminal pin 62 of theUOC ICIC601 is used.
This results in data being fed via Q1103, Q1105 and
Q1104 to the UOC IC IC601 pin 62.
The type of data and function control information fed
via the Q-Link is as follows:
TV Auto Power ON: TV automatically turns ON
when the VCR starts play-back.
VCR Auto Standby: VCR will automatically
switch to standby when the TV is turned OFF,
unless the VCR is in recording mode.
TV On screen Display of VCR status.
Download of Country selection.
These above features will only work with a Panasonic
TV / video combination which are both Q-Link
(Project 50+) compliant.
The features below will work with different brands of
TV and video combinations, again as long as both TV
and video are Project 50 compliant.
Tuner preset data down load (TV->VCR)
What You See Is What You Record (Direct TV)
In addition to these features the TV/Video also
include in their protocol Automatic signal matching
(signal quality). Here the TV/video at first time of
connecting, exchange information regarding features
and operational capabilities, such as signal standards
and the ability to process and display 16:9 format, for
4.1.4. I2C Bus
Pins 2 / 3 - SCL / SDA
The I2C bus is a two-wire Bus system consisting of a
data line and a clock line. This BUS system allows
serial and bidirectional communications exchange
between several devices which include an I2C bus
interface. The number of connections are therefore
reduced, which results in a simplified circuit design
and increased reliability (less soldered
joints/connections and contacts).
Within the the UOC IC, the microcontroller stage and
the signal processing stage utilise this Bus.
4.2. Colour TV Signal Processing
The TDA9350/60/80 series of the Ultimate One Chip
(UOC) IC IC601 incorporates all the functions
necessary for processing of audio and video signals.
The following sections will include the video input and
output control, IF signal path, colour decoder and
RGB processing stages. Horizontal and Vertical
synchronisation are also included. The elements
required by the UOC IC to perform these functions
Multistandard vision IF circuit with constant PLL
Mono intercarrier sound FM demodulator or
QSS IF amplifier
Internal IF AGC timing
CVBS (internal/external) or Y/C signal source
Integrated chrominance trap circuit
Integrated luminance delay line with adjustable
Asymmetrical peaking in the luminance channel
Black stretching for non-standard luminance
Integrated chroma bandpass filter with
switchable centre frequency
PAL/NTSC or multistandard colour decoder with
automatic search system
internal baseband delay line
RGB control circuit with ’Continuous Cathode
Calibration’ and colour temperature option
Linear RGB or YUV input with fast blanking for
external RGB/YUV sources
Horizontal synchronisation with two control loops
and alignment-free horizontal oscillator
Vertical count-down circuit
Vertical driver optimized for DC coupled vertical
Horizontal and vertical geometry processing
Horizontal and vertical zoom function for 16:9
Horizontal parallelogram and bow correction for
large screen picture tubes.
4.3. IF Signal Processing
The IF signal processing for the Z8 chassis is carried
out by IC601. There are two main types of IF circuit
configurations used depending on the UOC IC device
used, these differences will be covered in the
4.3.1. Video (VIF) Processing Signal Path
TheRF signal received by the tuner TNR001 is output
via terminals IF1 and IF2. This IF signal is necessary
for processing of video (VIF) and sound (SIF) signals.
Here the signal path varies, depending on the version
of UOC IC used.
For stereomodels, the IF signal is passed through the
SAWfilter X103, where separation of the VIF and SIF
signals occur. Here, the VIF signals are fed to IC601
pins 23 and 24 where video processing takes place.
The internal circuit provides amplification,
demodulation and filtering. The signal level is
monitored by the internal AGC detector and the
information is fed back to the tuner via pin27 of IC601.
Formonomodels, the IF signal path sees the IF signal
being fed to the intercarrier SAW filter X102. From
here the signal feeds the UOC IC IC601 via pins 23
and 24 where video processing takes place internally.
4.3.2. Sound (SIF) Processing Signal Path
As alreadymentioned, the IF signal fed fromthe tuner
is necessary for the processing of sound (SIF)
signals. Once again, the signal path varies,
depending on the version of UOC IC used.
For stereo models, the SIF signal fed from the SAW
filter X103 is applied to IC601 pins 28 and 29, where
signal processing is provided internally within the IC.
Here the signal is split into two paths.
The first path feeds the signal through an internal
QuasiStereo Sound (QSS)mixer and bandpass filter,
to produce a QSS IF output at pin 35 via the audio
For mono models, the SIF signal path is fed to IC601
pins 23 and 24 via the intercarrier SAWfilter X102. As
already mentioned, separation of the VIF and SIF
signals occur internally within the UOC IC.
4.4. SECAM IF Signal Processing
Those models which are capable of processing
SECAM L signals have an additional IF signal path
from the tuner to the relevant video and audio signals
that are required.
The IF signal is fed from the tuner TNR001 via two
trap circuits, made up of X101, L105 and L106. For
SECAM processing, the IF signal splits into two
paths. These are discussed in the following sections.
4.4.1. Video (VIF) Processing Signal Path
For VIF processing of mono TVs, the IF signal is fed
from the tuner and via the intercarrier SAW filter
X102. This results in the VIF signal being input via
pins 23 and 24 of the UOC IC IC601.
For stereo models, the IF signal is fed via the SAW
filter X102 where the VIF signal is extracted before
being fed to IC601 pins 23 and 24.
4.4.2. Sound (SIF) Processing Signal Path
For mono models, the IF signal is fed from the tuner
and via the amplifier transistor Q204 and L/L’
switching circuit, made up of transistors Q202, Q203
and filter X201. The L/L’ operation is controlled by the
UOC IC IC601 pin 4 where the signal path is
determined by the switching of the control transistor
During L mode operation, pin 4 of IC601 is pulled low
causing transistor Q202 to be switched Off. With the
voltage at the collector of Q202 being High, the IF
signal will flow via transistor Q204, diode D202 and
pin 2 of filter X201. At the same time, transistor Q203
switches on causing the L’ input pin 1 of X201 to be
pulled Low, muting its operation.
During L’ mode operation, pin 4 of IC601 is held high
by resistor R209 causing transistor Q202 to switch
on. The voltage at the collector of Q202 is Low,
causing the IF signal to flow via transistor Q204,
diode D201 and pin 1 of filter X201. At the same time,
the L input pin 2 of X201 is pulled Low via transistor
Q203, muting its operation.
The SIF signal from X201 is fed via the IF inputs pins
1 and 16 of the AM demodulator/audio switch IC201.
The audio output at pin 8 is fed to the buffer transistor
Q208. Transistor Q209 is used to provide muting of
the audio signal when no SECAM signal is present at
the tuner input. Pin 7 of IC601 provides the trigger
voltage to Q209, the level being determined by the
presence of either positive (SECAM) or negative
(PAL/NTSC) modulation. From here the signal
follows two paths.
The first path feeds the audio signal to the UOC IC
IC601 pin 28 for further processing.
The second path sees the audio signal being output
via transistors Q3101 and Q3102 to the AV 21 pin
scart pins 1 and 3.
For stereo models, the IF signal is fed from the tuner
via the amplifier transistor Q204 and L/L’ switching
circuit asmentioned above. The SIF signal fromX201
is fed via pins 28 and 29 of the UOC IC IC601.
PANASONIC TX-25CK1C/M CHASSIS Z8 4.5. Video Signal Processing
The UOC IC IC601 carries out all the necessary
control operations required for video and audio
On stereomodels, the VIF signal is fed from the tuner
via the IF stage (discussed in section 4.3.1.) pins 23
and 24. Here the VIF signal is fed to the first
processing stage of IC601, which provides
amplification, demodulation and filtering, with the
resultant VIF signal being output via pin 38.
The SIF signal however, is input via pins 28 and 29,
the processing of which is discussed in section 4.3.2.
On mono models, the VIF / SIF signals are again fed
fromthe tuner via the IF stage. The IF signals are both
input via pins 23 and 24 to the first processing stage,
which again provides amplification, demodulation
and filtering. Here the VIF and SIF signals follow
different processing paths, which results in the VIF
signal again being output via pin 38, and the SIF
signal being fed to the internal audio processing stage
of IC601 discussed in section 4.7.
4.6. Video Processing
The VIF signal fed from the first stage of IC601 is
output via pin 38, as mentioned in the previous
At the output of pin 38, the VIF signal is fed back to
transistor Q601 where the VIF signal is buffered and
fed via a sound trap. This sound trap which is model
dependant, may consist of L601, X602, X603, L603
and X604. The VIF signal is then fed to buffer
transistor Q602 and is output at the emitter. Here the
video signal is split into two paths.
The first path sees the video signal being fed via
the buffer transistor Q3104, to pin 19 of the AV
21 pin scart terminal.
The second path from the emitter of Q602 feeds
the video signal back to IC601, where the signal
is input via pin 40.
The video signal which is input via pin 40 is fed to the
internal stages consisting of a video switch, video
ident and filters. The video switch of this stage is used
to select between following signals:
RF video input via pin 40 as already discussed.
Video input via pin 42, this video signal being
input via either the RCA video (located at the
front of the TV) or pin 20 of the AV 21 pin scart
The selected video signal is then fed to the video ident
stage, which is used to detect the presence of a video
signal input via either pin 40 or 42. Where a video
signal is present at the input of IC601, internal
synchronisation using the video signal occurs.
However, where the absence of a video signal is
detected, then synchronisation is internally
The selected video signal is also fed via the video
filters which produce luminance and chrominance
signals that follow separate processing paths.
4.6.1. Luminance Processing
The luminance signal is now fed via a delay line,
which compensates for the processing time
difference between the luma and chroma signals. The
luma signal is fed via a peaking circuit and a black
stretch correction stage, which provide black level
correction. The luma signal is then fed to the RGB
PANASONIC TX-25CK1C/M CHASSIS Z8 4.6.2. PAL Chrominance Processing
To process chroma signals, the output from the video
switching circuit is fed to the colour decoder stage.
Here the chroma signals are demodulated with the
resultant U/V signals being fed to the following
baseband delay line, which ensures the chrominance
and luminance signals are at the same timing.
The U/V signals are then fed to the RGB processing
Timing and synchronisation of the colour decoder
processing stage is achieved by using a 12MHz clock
signal fed from an internal reference oscillator of the
microcontroller stage. During SECAM processing,
this timing and synchronisation of the colour decoder
stage is achieved using the 12MHz clock and is set by
C604, located at pin 13 of IC601.
4.6.3. RGB Processing Stage
The luminance and chrominance signals fed fromthe
previously discussed processing stage are fed to a
switching circuit within the RGB processing stage.
Here at this switching circuit, the RGB and fast
blanking signals input via the AV 21 pin scart terminal
(JK3102) pins 15, 11 and 7 respectively, are fed to
IC601 pins 46, 47 and 48 with the blanking signal
being input via pin 45.
The signals fed to the switching circuit are firstly fed
via and RGB to YUV converter. From here the newly
converted YUV signals are then fed to the YUV
This YUV switching circuit which is controlled by the
fast blanking pulse input via pin 45, is used to select
between the internally processed luminance and
chrominance signals and newly converted YUV
The selected signals being fed via a saturation control
stage are then converted to RGB. The RGB signal is
then fed to the RGB stage of IC601.
4.6.4. RGB Output Stage
In this final processing stage of IC601 the RGB
signals from the RGB processing stage and the RGB
from the text / OSD generator (discussed in section
4.9.1.) are fed to a switching circuit. The selected
RGB signal is then fed via the contrast and brightness
control stages, which are also controlled by the Beam
Current Limit (BCL) information input via pin 49 of
IC601, as well as information fed from the CATS Eye
The RGB signal is then fed via the RGB output
amplifiers, which are controlled by the leakage and
cutoff currents (discussed in section 8.1.1.) fed back
from the colour output stage to IC601 via pin 49.
The RGB signal is then finally output from IC601 via
pins 51 (R), 52 (G) and 53 (B). The RGB signal is then
fed to connector E8 where this signal is fed to the
Y-Board and the colour output stage.
PANASONIC TX-25CK1C/M CHASSIS Z8 4.7. Audio Signal Processing
As already mentioned in section 4.3.2. the SIF signal
fed from the tuner follows a number of different paths
dependant upon the model and UOC IC IC601
4.7.1. Stereo Models
The SIF signal input via pins 28 and 29 of IC601 are
processed internally, with the signal being fed via a
Quasi Stereo Sound (QSS) mixer and bandpass filter
which is used to produce a QSS IF output at pin 35
This QSS IF signal is then fed via transistors Q2004
/ Q2003 to the MSP3415D pin 47 of IC2001
(described in section 10.).
4.7.2. Mono models
On mono models the UOC IC IC601 internal
processing differs from that used by the stereo
versions of the UOC IC.
The SIF signal fed from the tuner is input via pins 23
and 24. Here the SIF signal which is fed via the first
processing stage, provides amplification and filtering
using an internal bandpass filter.
The SIF signal is then fed via the following
demodulator stage to the audio switch and Automatic
Volume Level (AVL) control stage. Also input directly
to this stage via pin 35 of IC601 is the audio signal
input via either the 21 pin scart terminal or the RCA
Here these signals are fed to a selection switch where
the selected audio signal is then fed to the AVL control
stage, this feature being model dependant.
The AVL control stage is used to automatically
stabilise the audio signal output to a set level,
reducing the effects of varying audio levels which
occur between different programmes.
The audio signal is then output via pin 44 of IC601,
where the signal is then fed to the audio output IC
The audio signal output via pin 28 of IC601 to
transistors Q3101 and Q3102 where the signal is
amplified and buffered before being fed to pins 1 and
3 of the 21 pin scart terminal.
PANASONIC TX-25CK1C/M CHASSIS Z8 4.8. SECAM Audio Signal Processing
4.8.1. Stereo Models
On SECAM stereomodels, the SIF signal is input via
pins 28 and 29 where the processing mentioned in
section 4.4.2. is performed. This results in a QSS IF
signal being output via pin 35. This signal being fed
via transistors Q2004 and Q2003 to the MSP3415D
pin 47 of IC2001 (discussed in section 10.).
Where an AM audio signal is required for further
sound processing, the SIF signal is passed through
an AM demodulator and output via pin 44. This signal
being fed to the MSP3415D pin 44 of IC2001
(discussed in section 10.).
4.8.2. Mono Models
On SECAM mono models, an FM modulated SIF
signal fed from the tuner is also input via pins 23 and
24 (mentioned in section 4.4.).
However, where an AM modulated SIF signal is
received, this signal is fed to an additional IC in the
form of IC201 (TDA9830), discussed in section 12.1.
This ICis required todemodulate theAMsignal as the
mono version of the UOC IC IC601 does not contain
an AM demodulator stage.
This AM signal which is output from X201 is fed to
IC201 pins 1 and 16. The resultant signal is output at
pin 8 and fed viaemitter follower transistorQ208. This
AMSIF signal is then split into two paths as discussed
in section 4.4.2, with one path feeding the AM audio
signal to pin 28 of IC601.
Here the audio signal undergoes the processing
discussed in section 4.7.2. which results in the audio
signal being fed via the Automatic Volume Level
(AVL) control stage.
The audio signal is then output via pin 44 of IC601,
where the audio signal is fed to the audio output IC
IC251. The audio signal which is output from the 21
pin scart terminal is fed from IC201 via transistors
Q3101 and Q3102.
It should be noted that pin 28 of IC601 has two
functions depending on the signal being processed.
Where SECAM signals are being processed, pin 28
is an input for the AM SIF signal fed from IC201.
For PAL / NTSC operation, pin 28 is an output which
allows the audio signal to be fed to the 21 pin scart
PANASONIC TX-25CK1C/M CHASSIS Z8 4.9. Teletext Processing Stage
In addition to the TV signal and control processing
capabilities of the UOC IC IC601 already briefly
mentioned earlier, the device also performs teletext
processing. The features included within the IC to
perform teletext processing are shown below.
Text memory for 1 or 10 pages
Data Capture for US Closed Caption
Data Capture for 525/625 line World System
Teletext (WST), Video Programme Signal (VPS)
and Wide Screen Signalling (WSS) bit decoding
Automatic selection between transmission
Real time capture and decoding for WST in
hardware, to enable optimized UOC IC
Automatic detection of FASTEXT transmission
Signal quality detector for video and WST/VPS
Comprehensive teletext language coverage
Full Field and Vertical Blanking Interval (VBI)
data capture of WST data
4.9.1. Teletext Operation
To enable teletext processing, the CVBS signal and
sync pulse is applied to the teletext acquisition stage.
Here the signal is converted into a digital formand the
synchronisation information is used to produce a
The acquisition stage extracts the transmitted text
data and stores it into the page memory, where it is
held until this data is requested. The microcontroller
detects the requisition of the teletext data and when
selected, the information is fed to the display/OSD
generator. The pixel information from the page
memory is translated into RGB values. The
generation of the pixel clock is created internally by
the display timing stage which is fed a horizontal and
vertical sync signal via the internal drive circuits.
The RGB text data and fast blanking information is
translated via the internalRGB processing stage. The
output path is described in section 4.6.4.
PANASONIC TX-25CK1C/M CHASSIS Z8 4.10. Synchronisation and Deflection
The UOC IC IC IC601 contains separator circuits for
the horizontal and vertical sync pulses. These signals
are used to produce the horizontal, vertical and E/W
drive pulses. Synchronisation is processed internally
within IC601. This processing circuit allows the
following geometry parameters to be adjusted, which
are carried out by software control.
For those models which have East-West correction
included, the additional adjustments are given below.
EW parabola width
EW upper and lower parabola correction
To carry out synchronisation and deflection
processing, the luma signal from the video switch
circuit is applied to the internal sync separator.
PANASONIC TX-25CK1C/M CHASSIS Z8 4.10.1. Horizontal Drive Processing
The horizontal signal fed from the sync separator is
passed via an internal PLL which is controlled by a
25MHz Voltage Controlled Oscillator (VCO).
The horizontal drive pulse is then output from pin 33
of IC601, synchronised by the horizontal flyback
pulse input via pin 34.
The horizontal output frequency decreases from
35KHz to 15.625KHz during switch On/Off times,
thereby reducing the load on the horizontal output
transistor Q501 during these periods.
4.10.2. Vertical Processing
The vertical pulse produced by means of a vertical
divider circuit is fed a vertical sync signal and is output
fromthe separator stage. This pulse is fed to a vertical
sawtooth generator, which is used to produce the
vertical and EW drive signals. The vertical pulse is
also input to the sandcastle generator which outputs
a two level sandcastle pulse via pin 34. The clock
signal to the vertical divider is achieved by means of
a burstkey pulse fed from the horizontal oscillator.
The sandcastle pulse, output via pin 34 of IC601 is
used to generate a higher level signal on to the
incoming flyback pulse which is used to provide
horizontal blanking of the RGB outputs
4.10.3. Geometry Processing
The vertical pulse fed to the vertical sawtooth or ramp
generator is then processed, thus producing a
sawtooth whose amplitude is determined by the
external RC components at pins 25 and 26 of IC601,
made up of R603 and C614. The output path of the
vertical sawtooth generator is split into two paths.
The first path sees the signal being input to the
vertical geometry processor. This provides a
differential drive signal which is output from pins 21
and 22, and fed to the vertical output IC IC451 pins 4
(V+) and 5 (V-).
The second path feeds theEast-West (EW)geometry
processor. This function is available for large screen
TVs of 25" and above, and is used to provide
additional vertical correction. The EW drive to the
correction stage is output from pin 20 of IC601.
An overvoltage protection input is provided at pin 36,
which is fed via the internal overvoltage detector, to
trigger the slow start and stop circuits, switching the
TV into standby.
PANASONIC TX-25CK1C/M CHASSIS Z8 5. Horizontal Output
The line frequency pulses for the horizontal driver
stage are output from pin 33 of IC601 and fed to the
horizontal drive transistor Q501. The transistor has a
transformer T553 at its collector, which is used to
provide AC coupling and impedance matching with
the horizontal transistor Q551.
To ensure that transistor Q501 is not damaged by
excessive spikes generated by back EMF of the drive
transformer, a filter network R504 and C502 are
connected across the collector-emitter terminals of
The horizontal output transistor Q551 is used to drive
the horizontal deflection coils and FBT.
Linearity is provided by a group of components made
up of R561, C562, L502, C563, L501, R560, L551 and
diode modulators D556 and D557.
The horizontal output stage provides deflection
current for the scan coils, EHT for theCRT and supply
lines for peripheral circuits.
PANASONIC TX-25CK1C/M CHASSIS Z8 6. Vertical Output
The vertical timebase functions are provided in two
parts, IC601 which produces the synchronisation,
vertical oscillation and control, while the vertical drive
for the deflection coil is provided by IC451.
The vertical drive signal outputs, Vout(-) and Vout(+)
are fed from IC601 pins 21 and 22, to form a
differential output current which is fed to the vertical
output IC IC451 pins 4 and 5. A resistor R602 is
connected across the vertical drive signal path and is
responsible for determining the output current
through the deflection coil.
This vertical output IC IC451 consists of an
operational amplifier. The pre-amplified sawtooth
waveform is passed to the op-amp, resulting in a
vertical drive pulse being output via pin 2 of IC451.
The gain of the internal op-amp is controlled by the
negative feedback pulse. This pulse is fed via R415
and R407, connected between pin 2 and pin 5.
IC451 also contains a Pump Up circuit which is used
to provide a switching voltage for the vertical flyback
period. This is required since the energy requirement
of the vertical output stage is highest during flyback,
where the electron beam has to be passed rapidly
from the bottom right hand corner of the screen to the
top left corner of the screen.
During vertical sweep, the bootstrap capacitor C406
is charged up to almost supply voltage via D402. The
output of the pump up generator pin 7 of IC451 is at
ground potential at this time.
As a result of the DC, displacement at the negative
pole of capacitor C408 (rising to the supply voltage),
build up of the supply voltage for the output stage at
pin 3 rises to almost twice the supply voltage. At the
same time, D402 is reverse biased and thus prevents
discharge of C406 into the supply line.
6.1. Vertical Protection
The vertical protection circuit is made up of
transistors Q401 and Q402, whichmonitors the state
of the vertical output and feeds the result back to the
UOC IC IC601 pin 36 via the EHT / over-voltage
protection circuit, made up of D603 and Q603.
During normal operation Q402 is baised On by the
switching voltage output from pin 7 of IC451. With
Q402 conducting, transistor Q401 is switched Off
resulting inQ603 remainingOff and pin 36 of theUOC
IC IC601 remains High. This High level being fed via
R2022, which ensures that the protection circuit does
In the event of a vertical output failure the base bias
of Q402 falls, resulting in Q402 switching Off.
ConsequentlyQ401 is biasedOn via R410 and C410.
WithQ401 conducting, D603 also conducts due tothe
voltage drop at its cathode, which causes transistor
Q603 to conduct. Hence, the protection input via pin
36 of theUOCICIC601 is switched High. After a short
delay, IC601 switches the TV into standby.
As well as the safety circuit just described the output
at pin 2 of IC451 is also thermally protected by an
internal protection stage. This thermal protection
stage is used to respond to temperature change and
limit the driving currents so that no further
temperature rise can occur. This ensures that the
output stage can only be operated within the
permissible operating range.
PANASONIC TX-25CK1C/M CHASSIS Z8 7. East-West Correction
The Z8 chassis includes an improved East-West
correction circuit, which compensates for the
pincushion distortion in the east-west direction (for
110 degreeCRT’s). This is achieved by increasing the
horizontal deflection current at vertical centre in
relation to vertical start and vertical end.
East-West correction is achieved by the horizontal
deflection current being influenced by a vertical
frequency parabola signal in the east-west diode
modulator D556 and D557.
The EW drive signal is output from pin 20 of IC601
and applied via resistor R715 and buffer transistor
Q701 before being input at pin 7 of the East-West IC
The EWdrive signal is fed to a comparator, where the
signal is compared with the horizontal flyback pulse,
input at pin 8. A parabola waveform is then output
from pin 5 of IC701 where the signal is fed via
transistor Q702. Here the parabola waveform is
inverted, and fed to D701.
D701 is a photocoupler which provides drive current
to the ’hot’ side of the circuit as well as isolation
between ’hot’ and ’cold’ circuits.
The parabola signal is fed to transistor Q751, where
the signal is amplified and applied to the drain
terminal of the FET transistor Q752. This ensures
that the deflection current is increased at field scan
centre and reduced towards the start and end of field
The EW signal is superimposed onto the deflection
current with the aid of the diode modulator D556 and
D557, thus performing EW correction.
Transistor Q753 is used to monitor and regulate the
output current of the EW modulator circuit D556 and
When and increased current occurs, a voltage drop
is developed across resistor R762, resulting in an
increased conduction of Q753. This in turn reduces
the charge of capacitor C754 and hence, the
conduction of the photocoupler D701. In this way the
EW current is regulated.
PANASONIC TX-25CK1C/M CHASSIS Z8 8. Memory (EEPROM)
Thememory IC IC1103 is interfaced with the UOC IC
via the I2C bus. The following data is memorised by
the memory IC.
Picture Geometry adjustments
Model features (option bytes)
Tuning data for 100 programme positions
SIF data SC1/SC2
Colour system (PAL, SECAM or NTSC)
Last Memory Information
Power on/off condition
PANASONIC TX-25CK1C/M CHASSIS Z8 9. Colour Output
The colour output stage receives the RGB signals
and provides processing for display on the CRT. This
is performed by the Triple Video Output IC IC351,
which is located on the Y-Board.
The Z8 chassis uses two variations.
TDA6107 is used on TVs with CRT’s below 25".
TDA6108 is used on 25" and 28" TVs and has an
increased bandwidth as well as being able to
withstand higher current.
Besides the differences mentioned above, both
devices are pin compatible and their basic operation
9.1. Colour Output Stage
In order to avoid damage caused by long cathode
lines and thereby trim the frequency response, the
RGB output stage is mounted onto the CRT board.
The use of IC351 means that the number of
components are reduced to a minimum.
The RGB signals fed to the colour output stage are
driven from the UOC IC IC601, located on the
E-Board from pins 51, 52 and 53 via connectors E8
and Y2 pins 3, 2 and 1. The signals are fed directly to
IC351 pins 1(B), 2(G) and 3(R).
The RGB signals input to IC351 are amplified before
being output via pins 7(R), 8(G) and 9(B).
9.1.1. Cut-off Control Circuit
The leakage current and cut-off evaluation circuits of
UOC IC IC601 are used for the adjustment of the
output amplifiers, which are used to keep the picture
independent of ageing.
The cut-off control is a scan regulating circuit, which
electronically regulates for dynamic component
tolerances and the effects of wear and tear on the
picture tube etc.
It also offers the following advantages:
Automatic black level compensation
Prevention of colour purity errors during CRT
heating up time and stabilisation of excessive
ageing in the initial hours of operation.
During field flyback, the leakage current from theCRT
system is measured at ultra black before the RGB
cathode currents are measured. These measured
values are output at pin 5 of IC351 via connector Y2
pin 5, and applied to theUOCIC IC601 pin 50, located
on the E-Board.
The results of these measurements are then used in
the internal RGB processing and control stages of
IC601, compensating for CRT and component
9.1.2. Switch-off Fluorescence Suppression
If the CRT is slow to discharge at switch-off, afterglow
flecks would occur. This is suppressed by transistor
At switch on and during operation of the colour output
stage, C370 is charged. However, Q351 has no
effect, since the base of Q351 is more positive with
respect to its emitter so Q351 is non-conducting.
At switch-off, Q351 is switched On by the rapid
decrease of the supply line. Diode D373 becomes
reversed biased due to the charge held in capacitor
C370. This causes Q351 to become conductive so
C370 discharges via the emitter/collector junction of
Q351 and diodes D370, D371 and D372. This drives
the internal op-amps further and increases the output
of the op-amp, preventing afterglow. By the time the
capacitor C370 has discharged and the circuit
becomes inoperative, the CRT has discharged.
9.1.3. Beam Current Limiting
The CRT beam current is monitored from pin 3 of the
FBT T552, which works with virtual earthing. As the
beam current increases, an increasingly negative
charge is developed across capacitor C558. This
negative charge is fed to the BCL input of the UOC IC
IC601 pin 49 via resistors R628 and R624, where the
current level ismonitored and compared to an internal
reference within the UOC IC. The result is used to
reduce the drive of the brightness and contrast
However, If the beam current fails to be reduced, the
safety circuit is used to switch the TV off. If the beam
current reaches the maximum control range of the
FBT, the zener diode D403 conducts, causing diode
D603 to conduct. This negative charge is applied to
the base of transistor Q603, causing Q603 to switch
On. With the protection input pin 36 of the UOC IC
IC601 biased by resistors R2022 and R621, the
switching action of Q603 now increases the voltage
at pin 36 of IC601, switching this input High. After a
short delay the TV will be switched into standby.
PANASONIC TX-25CK1C/M CHASSIS Z8 10. MSP3415D Audio Signal Processing
The MSP3415D IC2001 is designed as a
Multi-standard Sound Processor for processing of
analogue and digital audio signals. This device is
model dependant and is used on stereo models only.
The MSP3415D IC2001 provides full TV sound
processing, starting with analogue sound IF signal-in,
down to processed analogue AF-out, within a single
chip which covers all European TV standards. As well
as processing of the analogue audio signals, theMSP
also processes the NICAM signal fed from the IF
The MSP3415D IC2001 is designed to
simultaneously perform digital demodulation and
decoding of NICAM-coded TV stereo sound, as well
as demodulation of FM-mono TV sound.
Alternatively, two carrier FM stereo can also be
processed within the MSP.
However when receiving an AM sound carrier the
demodulation is still carried out in the IF stage, from
here the AM sound is fed to the MSP for further
IC2001 offers the following advantages :
Analogue Sound IF input
Automatic Gain Control (AGC) for analogue
Stereo baseband input via integrated A/D
All demodulation and filtering is performed on
chip and individually programmable
Simple switching between NICAM standards.
(B/G, I, L and D/K)
No external filter hardware required
Only one crystal clock required (18.432MHz)
The features of the IC2001 section are:
Flexible selection of audio sources to be
Performance of all terrestrial de-emphasis
systems (FM, NICAM)
Digitally Performed FM-identification decoding
Digital baseband processing: volume, bass,
treble, loudness, and spatial effects
Simplified controlling of volume, bass, treble etc.
10.1.1. Architecture of the MSP3415
The diagram below shows a simplified block diagram
of the MSP. Its architecture is split into three
Demodulator and decoder section
Digital signal processing (DSP) section,
performing audio baseband processing
Analogue section containing two A/D converters
and four D/A converters and SCART switching
10.2.1. Analogue Sound IF - Input
The tuner/IF stage located on the E-Board, feeds the
SIF signal, either Wagner stereo or NICAM from the
UOC IC IC601 pin 35, and via amplifier transistors
Q2004 and Q2003, before being input via pin 47
(ANA_IN1) of IC2001.
Models which are able to process SECAM L standard
use two traps X2002 and X2003 which are placed at
the base of Q2004, these being 6.5MHz and 7.0MHz
respectively. The traps are used to prevent
interference of the Wagner or NICAM stereo signal
present in the IF signal. The signals at this stage have
not been demodulated.
If AM sound is being received, this signal is firstly
demodulated in the UOC IC IC601 and output at pin
44 before being passed to the MSP. The AM
demodulated sound is fed to the MSP3415D IC2001
via pin 44.
NICAM which is a high quality stereo signal, uses the
sound coding format known as Near Instantaneous
Companding Audio Multiplex system, the NICAM
system being added to the already existing FM
When in NICAM / FM mode there are three different
audio modes possible :
NICAM - Stereo transmission
Dual language transmission (where available)
Information regarding the transmission type and
about the quality of the NICAM signal can be read by
the NICAMdecoder via the I2C bus. In the case of low
quality (high bit error rate) the MSP can decide to
switch to an analogue FM mono sound signal.
When Wagner stereo, which is a 2 carrier system, is
transmitted an identification signal is also transmitted
along with the second sound carrier.
This identification signal which is a 54.7KHz
amplitude modulated pilot signal carrier is
suppressed so that only themodulated characteristic
frequencies are made available for further
Operating mode Characteristic Frequency
Dual Tone 274.1Hz
These characteristic frequencies are fed to the signal
identification circuit, here the type of signal
transmission is identified, with the following switching
being made available :
FM - Stereo transmission
Dual tone transmission (where available)
FM. - Mono
This identification signal is also used to inform the
MSP as to which of the above three modes is being
transmitted, this information being fed via the I2Cbus.
The UOC IC IC601 then uses this information to
trigger the required switching and OSD display for
When NICAM/ FMorWagner stereo IF sound signals
are input to theMSP IC2001, the signals are firstly fed
via an analogue AGC circuit. This AGC circuit is used
to provide an optimum signal level for a wide range of
input levels. This AGCcircuit can also be set to a fixed
input range. To provide the optimum level the input
range of the A/D converter should be completely
covered by the sound source. From the output of the
AGC circuit the SIF signal is then fed to an A/D
converter, where the signal is converted to digital.
From the output of the A/D converter, the signal
processing splits into two paths.
SIF channel 1
SIF channel 1 is used to process NICAMor FM2,
this being sound carrier 2 of the FM stereo
SIF channel 2
SIF channel 2 is used to process FM mono or
FM1, again this being sound carrier 1 of the FM
10.2.2. Clock Generator
To aid processing an external crystal is connected to
pins 51 and 52 of IC2001. This provides the required
audio clock frequency for audio processing.
For NICAM / FM Mono processing, theMSP requires
a clock frequency of 18.432MHz, which it uses to lock
to the sampling rate of the NICAM signal.
When processing FM-stereo, the system clock runs
free on the crystal’s 18.432MHz signal.
10.2.3. Demodulation Stage
The digitised IF sound signals fed from the A/D
converter are then fed to two Quadrature mixer
circuits. By means of the two programmable
quadrature mixers, two different audio signals e.g.
NICAM and FM-mono signals can be input.
Depending on the selected standards, this audio
information could have a frequency range of 0 to
From the Quadrature mixers the signals are then fed
via a lowpass filter, these filters being programmable
make it possible to process both NICAM standards.
Control of these filters are carried out by the UOC IC
via the I2C bus.
From the output of the low pass filters the signals are
then fed to the Phase and AM Discriminator stage.
From the output of this stage the FM and NICAM
processing follow different paths.
The NICAM signal is fed via the DQPSK decoder,
from the output of the decoder we now have a data
stream of 728k bits/sec which is fed to the NICAM
For FM processing the demodulated signals are fed
to two differentiator circuits which differentiate the
phase information output from the demodulator
circuit to complete the FM demodulation.
10.2.4. NICAM Decoder
Before any NICAM decoding can start, IC2001 must
first lock to the NICAM frame structure by searching
and synchronizing to the Frame Alignment Word
To reconstruct the original digital sound samples, the
NICAM - bitstream has to be descrambled,
deinterleaved and rescaled, as well as performing bit
error detection and correction, all of which are carried
out in this section.
To switch the TV set to the actual soundmode, control
information on the NICAM mode and bit error rate are
supplied by the NICAMdecoder via the I2C bus to the
UOC IC IC601. The UOC IC then, as mentioned for
FM processing, initiates the required switching and
OSD display for user information. From the output of
the NICAM decoder the left and right channels in
digital format are fed to the DSP processor stage.
10.2.5. FM Processing
After the FM signal has been demodulated the signal
is fed to aMute stage which is controlled by the carrier
detector circuit. If no FMcarrier is detected in channel
2 of the MSP then the subsequent FM1 output is
muted by the muting stage in that channel. Likewise,
if no FM2 carrier is detected in channel 1, the FM2
output will bemuted. This muting stage is provided to
prevent the processing of a noise signal to the
Fromthe output of themuting circuit, the signal is also
fed to the DSP after passing a lowpass filter, here the
demodulated FM/ AMsignals are decimated to a final
sampling frequency of 32KHz.
The usable bandwidth of the baseband signal being
10.2.6. MSP3415D Audio Baseband
By means of the DSP processor all audio functions
are performed by digital signal processing. The DSP
functions being grouped into three processing parts
The input pre-processing is intended to prepare the
various signals of all input sources in order to form a
standardised signal at the input to the channel
selector. The signals are adjusted in volume, by the
prescaler, before being processed with the
appropriate de-emphasis. When transmitting an FM
stereo signal, sound carrier1 is made up of L + R/2
while the second sound carrier FM2 ismade up of just
right hand signal. To produce a stereo signal the R/2
has to be removed from the ’Left’, this is performed in
the FM matrix stage.
Having prepared all the input signals to a
standardised level it is now possible with the aid of the
channel selector to distribute all possible signal
sources to the desired outputs.
All input and output signals can be processed
simultaneously with the exception of FM2, which
cannot be processed at the same time as NICAM.
This is due to the fact that NICAM and FM2
processing use SIF channel 1 in the demodulator
section. The processing of the NICAM and FM2
signals follow different paths controlled by an internal
switch, used to switch between the two processing
paths. This causes a delay during switching between
the two signal processing paths.
10.3. AM and SCART Processing
As mentioned at the start of the section on MSP3415
IC2001 processing, when receiving an AM
modulated signal, as is system ’L’, the signal is
demodulated in the IF stage. The audio signal is then
fed to IC2001 pin 44 mono input. The demodulated
AM audio signal is then fed to an internal analogue
scart switching circuit which is used to select between
the scart signals input via pins 41 and 42. The
selected audio signals are then fed via an A/D
converter before being input to the DSP processing
stage. Once the audio signals are fed to the DSP
stage, the signals are fed via a prescaler circuit which,
as mentioned previously, adjusts the volume of the
audio signals, thus ensuring the signals are at the
same standard as the other signal sources at the
channel select circuit.
10.4.1. Loudspeaker Output Path
When a signal source has been selected by the user
for output via the loudspeaker the signal is fed via a
stereo separation matrix circuit which is used only
when processing an FM stereo signal, at any other
time the circuit is switched off. From the output of this
circuit the signal is then fed to an Automatic Volume
Correction circuit, as well as Bass, Treble and
10.4.2. Automatic Volume Correction (AVC)
Different sound sources such as terrestrial and
satellite channels often have different volume levels.
Advertisements during movies usually have a higher
volume level than the movie itself. The Automatic
Volume Correction (AVC) solves this problem and
equalises the volume levels.
10.4.3. Bass and Treble adjustments
The Bass and Treble adjustments consist of two
separate filters. The control range is +20dB to -12dB
for Bass adjustment, and +15dB to -12dB for Treble
adjustment. These adjustments are carried out via
the OSD. The two filters coefficients for the selected
range are set to the required value via the I2C bus.
The volume modifications which occur during bass
and treble adjustments are stabilised by limiting the
internal volume, to prevent clipping, this limitation is
carried out via software.
The audio signal fed to the loudness stage is
examined for loudness and aurally compensated for.
Loudness increases the volume of low and high
frequency signals while keeping the amplitude of the
1KHz reference frequency constant.
As the loudness is set according to the actual volume
setting, the required filter coefficients must be
established first, before the signals are acted upon
with varying degrees of severity according to the
11. AF Output Stage
The Z8 chassis uses two audio output ICs. TDA7253
is a mono audio amplifier and TDA7263 is the stereo
version. Both versions include internal muting, short
circuit protection and thermal overload protection.
11.1. Audio Output Devices
TDA7253 is a single output audio amplifier used on
mono models only. The amplitude controlled AF
signal is output from the audio out terminal pin 44 of
the UOC IC IC601. The AF signal is fed to the audio
output stage via C263 and R256. This capacitor may
be charged up very quickly as all control processes
together with the baseband switch over are
processed in the UOC IC.
The AF signal is then input via pin 5 of the audio
output IC IC251. From here it is amplified and output
via pin 8. The AF signal is then fed via the headphone
terminal JK3101 to the internal speaker via connector
TDA7263 is a dual output audio amplifier used on
stereo models only. Both amplitude controlled AF
signals are output from pins 24(R) and 25(L) of the
MSP IC2001. The signals are fed to the base of
transistors Q2001 and Q2002. The transistors are
used for impedance matching in order that the
interference on the audio lines between the MSP
IC2001 and the audio output IC IC251 is kept at a
The left audio signal is fed via transistor Q2002,
R2001, C266 and R261 before being applied to the
audio output IC IC251 pin 1. The right audio signal is
fed via transistor Q2001, R2002, C263 and R256
before being applied to the audio output IC IC251 pin
5. These capacitors may be charged up very quickly
as all control processes (volume, balance) together
with the baseband switch over are processed in the
The AF signals input via pins 1 (L) and pin 5 (R) of the
audio output IC IC251,.are then amplified and output
via pins 8 (Rout) and 10 (Lout). Both AF signals are
fed via the headphone terminal JK3101 to the internal
speakers via connectors E6 and E7.
11.2. Mute Functions
11.2.1. POP Mute
At pin 3 of IC251, a muting transistor Q255 is used to
prevent the internal amplifiers producing POP at
switch Off times. This is achieved by muting the
internal audio amplifiers during these periods.
The POP mute control is input at pin 3 of the audio
output IC IC251. Transistor Q255 provides the
switching of the mute function via R241. The control
signal that causes switching of Q255 is provided by
the POP mute control transistor Q253, which is used
to prevent POP during switch Off times. The base of
Q253 is held high via resistor R262 which is fed from
the standby rectifier output D1201.
At switch On, Q253 is non-conducting since the base
and emitter are near the same potential. Capacitor
C257 begins to charge towards the +8V supply at the
anode terminal of diode D260.
At switch Off, transistor Q253 base voltage
decreases, causing Q253 to switchOn. This is due to
the charge held by capacitor C257, which is
prevented from discharging into the decreasing
supply line by diode D260. C257 now begins to
discharge via the collector / emitter junction of Q253.
The increased voltage present at the potential divider
R264 and R268 causes transistorQ255 to switchOn.
This in turn, causes pin 3 of IC251 to be pulled Low,
resulting in the audio signals of IC251 being muted.
11.2.2. Active Mute
The active mute control is input at pin 3 of the audio
output IC IC251. Transistor Q255 provides the
switching of the mute function via R241. The control
path is fed from the mute terminal of the UOC IC
IC601 pin 11, which is pulled Low during normal
operation, is biased by resistor R1141 to the 5V
standby supply. During channel change, tuning and
muting operations, the Low level output from pin 11 is
disabled. This causes the voltage at the base of
transistorQ255 to increase, switchingQ255 On. This
results in pin 3 of IC251 being pulled Low, resulting in
the audio output being muted.
12.1. SECAM AM Demodulator
French SECAM mono models require an additional
switching IC to process mono SIF signals. IC201
TDA9830 is a TV sound AM demodulator and audio
The SIF signal used for AM mono operation is fed
from the tuner via the IF processing stage (discussed
in section 4.4.2.) and fed via the IF inputs at pins 1 and
16 of the AM demodulator / audio switch IC201.
IC201 performs demodulation by passing the signal
through its internal processing stages. The
demodulated signal is output at the AM out terminal
at pin 6 of IC201, and is fed back into pin 7 of IC201
via decoupling capacitor C214, where the switch is
held permanently On by pin 9 being inactive.
Capacitor C214 is used to prevent any effects of
switching on the input stage.
The audio switch is an operational amplifier whose
output is determined by the mute control at pin 12 of
IC201. This is controlled by the presence of either
positive (SECAM) or negative (PAL/NTSC)
modulation, the trigger voltage being provided by the
NEG/POS control terminal fed from pin 7 of the UOC
The audio signal path from the switch, output at pin
8 of IC201, is discussed in section 4.4.2.
12.2. Monitor Output
The Z8 chassis may be used as a monitor for use in
specialised applications such as surveillance. The Z8
monitor differs from the TV such that it does not
require an RF transmission signal via the tuner since
all video inputs and outputs are routed via the AV
sockets. Therefore, the tuner and IF input stages are
omitted in the Z8 monitor.
The Monitor Output circuit is used to provide
impedancematching to and from external video input
sources via the AV sockets. This allows several
monitors to be connected in cascade.
The video signal is input viaRCA video (located at the
front of the monitor) or pin 20 of the AV 21 pin scart.
From here the video signal input level and impedance
are matched by the terminator resistor R3115 to
provide a 1V video input level. This video input is split
into two paths.
The first path sees the video signal being input via pin
42 of the UOC IC IC601 where processing is
performed as discussed in section 4.6.
The second path is fed via capacitor C3106 and
resistor R3113 to amplifier transistor Q3105. The
signal is then fed via resistor R3135 to matching
transistor Q3106. This provides the matching
necessary to output to an external video source.
Fromhere the signal is fed to the video output path via
buffer transistor Q3104 as discussed in section 4.6.
The video signal is output via pin 19 of the 21 pin scart
PANASONIC TX-25CK1C/M CHASSIS Z8 CIRCUIT DESCRIPTIONS:
LA7845 Vertical Deflection Output Circuit
The LA7845 is a vertical deflection output IC for highresolution
television and CRT display systems that use a
bus controller system signal processing IC. It can directly
drive the deflection yoke (including the required DC
component) from the bus controller system signal
processing IC's sawtooth waveform output. Connecting
the LA7845 and a Sanyo TV bus control system signal
processing IC in the LA7615 series allows all functions of
a color television signal system to be processed by the bus
system. Since the LA7845 has a maximum deflection
current of 2.2 Ap-p, it is optimal for use in large aperture
products, and is capable of driving 33 to 37 inch class
• Low power dissipation due to the provision of a built-in
• Vertical output circuit
• On-chip thermal protection circuit
• Good crossover characteristics
• Supports DC coupling.
PANASONIC TX-25CK1C/M CHASSIS Z8 TEA2031A COLOR TV EAST-WEST CORRECTION
The TEA2031A is intended to ensure frame rate
modulated parabolic and keystone corrections to
the horizontal deflection circuitry of 110° color TV
The linear frame saw-tooth is applied to appropriate
circuitry from which a corresponding parabolic
waveforms is obtained. This waveform is then fed
to a comparator together with the linear line sawtooth
for comparison. Comparator’s output drives
the output power stage which is capable of sinking
the external coil currents of up to 0.5A.
An internal recovery diode feeds back to the power
supply the coil fly-back current pulses of as high as
■ BUILD IN FRAME PARABOLA FROM
■ PARABOLA CORRECTION ADJUSTMENT
■ KEYSTONE CORRECTION ADJUSTMENT
■ LINE SIZE ADJUSTMENT
■ LINE DYNAMIC CORRECTION POSSIBILITY
■ D CLASS OUTPUT MODULATOR WITH
BUILD IN RECOVERY DIODE
■ 50 OR 60Hz OPERATION
■ LOW DISSIPATION
■ FEW EXTERNAL COMPONENTS.
The TEA2031A is intended to provide to 110° color
TV sets a parabolic and keystone frame rate modulated
correction in addition to the main horizontal
A stable 6.3V internal reference provides current
and voltage references to the whole IC.
Pins 1 and 2 are two symmetrical inputs of an onchip
multiplier circuit and are internally held at
6.3V reference potential level. Current inputs to
these pins are drawn from external sources via appropriate
resistors. The frame saw-tooth waveform
which has a peak-to-peak value of around 3
volts and a mean value of about 2.5 volts, supplies
Likewise, the current to pin 2 is drawn through a
series resistor from an external dc voltage source.
These series resistors can have values of around
40kΩ resulting in input currents of approximately
0.1mA ± modulation current.
Pin 7 should be loaded to ground through a 100kΩ
resistor which as a result will produce a parabola
of 5 volts peak-to-peak at pin 7. This parabola is
symmetrical if the DC current flowing into pin 2 is
equal to the mean input current of pin 1. Otherwise,
the parabola becomes dissymmetrical and
produces a keystone effect correction.
The line saw-tooth at pin 8 is obtained by feeding
the line fly-back voltage through an integrator network
formed by a diode and a grounded capacitor
(see typical application diagram). The DC component
of the line saw-tooth is compensated by an internal
current sinking source ; so that the mean DC
values of line saw-tooth and frame parabola voltages
Line saw-tooth and frame parabola signals are applied
to a comparator whose output is in the form
of width modulated pulses. During every pulse duration,
the output (pin 5) can sink external coil currents
of up to 0.5A associated with diode
modulator of the main horizontal scanning circuit.
An internal recovery diode feeds back the fly-back
energy of the coil to the power supply. This diode
can carry currents of up to 0.5A.
PANASONIC TX-25CK1C/M CHASSIS Z8 MSP 34x1G Multistandard Sound Processor Family with Virtual Dolby Surround
The MSP 34x1G family of single-chip Multistandard
Sound Processors covers the sound processing of all
analog TV-Standards worldwide, as well as the NICAM
digital sound standards. The full TV sound processing,
starting with analog sound IF signal-in, down to processed
analog AF-out, is performed on a single chip.
Figure 1–1 shows a simplified functional block diagram
of the MSP 34x1G.
The MSP 34x1G has all functions of the MSP 34x0G
with the addition of a virtual surround sound feature.
Surround sound can be reproduced to a certain extent
with two loudspeakers. The MSP 34x1G includes our
virtualizer algorithm “3D-PANORAMA” which has been
approved by the Dolby1) Laboratories for compliance
with the "Virtual Dolby Surround" technology. In addition,
the MSP 34x1G includes our “PANORAMA” algorithm.
These TV sound processing ICs include versions for
processing the multichannel television sound (MTS)
signal conforming to the standard recommended by
the Broadcast Television Systems Committee (BTSC).
The DBX noise reduction, or alternatively, MICRONAS
Noise Reduction (MNR) is performed alignment free.
Other processed standards are the Japanese FM-FM
multiplex standard (EIA-J) and the FM Stereo Radio
Current ICs have to perform adjustment procedures in
order to achieve good stereo separation for BTSC and
EIA-J. The MSP 34x1G has optimum stereo performance
without any adjustments.
All MSP 34x1G versions are pin and software downward-
compatible to the MSP 34x0D. The MSP 34x1G
further simplifies controlling software. Standard selection
requires a single I2C transmission only.
The MSP 34x1G has built-in automatic functions: The
IC is able to detect the actual sound standard automatically
(Automatic Standard Detection). Furthermore,
pilot levels and identification signals can be evaluated
internally with subsequent switching between mono/
stereo/bilingual; no I2C interaction is necessary (Automatic
The ICs are produced in submicron CMOS technology.
The MSP 34x1G is available in the following packages:
PLCC68, PSDIP64, PSDIP52, PQFP80, and
Architecture of the MSP 34x1G Family
Fig. 2–1 on page 9 shows a simplified block diagram of
the IC. The block diagram contains all features of the
MSP 3451G. Other members of the MSP 34x1G family
do not have the complete set of features: The
demodulator handles only a subset of the standards
presented in the demodulator block; NICAM processing
is only possible in the MSP 3411G and
2.2. Sound IF Processing
2.2.1. Analog Sound IF Input
The input pins ANA_IN1+, ANA_IN2+, and ANA_IN-
offer the possibility to connect two different sound IF
(SIF) sources to the MSP 34x1G. The analog-to-digital
conversion of the preselected sound IF signal is done
by an A/D-converter. An analog automatic gain circuit
(AGC) allows a wide range of input levels. The highpass
filters formed by the coupling capacitors at pins
ANA_IN1+ and ANA_IN2+ see Section 8. “Appendix
E: Application Circuit” on page 100 are sufficient in
most cases to suppress video components. Some
combinations of SAW filters and sound IF mixer ICs,
however, show large picture components on their outputs.
In this case, further filtering is recommended.
2.2.2. Demodulator: Standards and Features
The MSP 34x1G is able to demodulate all TV-sound
standards worldwide including the digital NICAM system.
Depending on the MSP 34x1G version, the following
demodulation modes can be performed:
A2 Systems: Detection and demodulation of two separate
FM carriers (FM1 and FM2), demodulation and
evaluation of the identification signal of carrier FM2.
NICAM Systems: Demodulation and decoding of the
NICAM carrier, detection and demodulation of the analog
(FM or AM) carrier. For D/K-NICAM, the FM carrier
may have a maximum deviation of 384 kHz.
Very high deviation FM-Mono: Detection and robust
demodulation of one FM carrier with a maximum deviation
of 540 kHz.
BTSC-Stereo: Detection and FM demodulation of the
aural carrier resulting in the MTS/MPX signal. Detection
and evaluation of the pilot carrier, AM demodulation
of the (L-R)-carrier and detection of the SAP subcarrier.
Processing of DBX noise reduction or
MICRONAS Noise Reduction (MNR).
BTSC-Mono + SAP: Detection and FM demodulation
of the aural carrier resulting in the MTS/MPX signal.
Detection and evaluation of the pilot carrier, detection
and FM demodulation of the SAP subcarrier. Processing
of DBX noise reduction or MICRONAS Noise
Japan Stereo: Detection and FM demodulation of the
aural carrier resulting in the MPX signal. Demodulation
and evaluation of the identification signal and FM
demodulation of the (L-R)-carrier.
FM-Satellite Sound: Demodulation of one or two FM
carriers. Processing of high-deviation mono or narrow
bandwidth mono, stereo, or bilingual satellite sound
according to the ASTRA specification.
FM-Stereo-Radio: Detection and FM demodulation of
the aural carrier resulting in the MPX signal. Detection
and evaluation of the pilot carrier and AM demodulation
of the (L-R)-carrier.
The demodulator blocks of all MSP 34x1G versions
have identical user interfaces. Even completely different
systems like the BTSC and NICAM systems are
controlled the same way. Standards are selected by
means of MSP Standard Codes. Automatic processes
handle standard detection and identification without
controller interaction. The key features of the
MSP 34x1G demodulator blocks are
Standard Selection: The controlling of the demodulator
is minimized: All parameters, such as tuning frequencies
or filter bandwidth, are adjusted automatically
by transmitting one single value to the
STANDARD SELECT register. For all standards, specific
MSP standard codes are defined.
Automatic Standard Detection: If the TV sound standard
is unknown, the MSP 34x1G can automatically
detect the actual standard, switch to that standard, and
respond the actual MSP standard code.
Automatic Carrier Mute: To prevent noise effects or
FM identification problems in the absence of an FM
carrier, the MSP 34x1G offers a carrier mute feature,
which is activated automatically if the TV sound standard
is selected by means of the STANDARD SELECT
register. If no FM carrier is available at one of the two
MSP demodulator channels, the corresponding
demodulator output is muted.
2.2.3. Preprocessing of Demodulator Signals
The NICAM signals must be processed by a deemphasis
filter and adjusted in level. The analog demodulated
signals must be processed by a deemphasis filter,
adjusted in level, and dematrixed. The correct
deemphasis filters are already selected by setting the
standard in the STANDARD SELECT register. The
level adjustment has to be done by means of the FM/
AM and NICAM prescale registers. The necessary
dematrix function depends on the selected sound standard
and the actual broadcasted sound mode (mono,
stereo, or bilingual). It can be manually set by the FM
Matrix Mode register or automatically set by the Automatic
2.2.4. Automatic Sound Select
In the Automatic Sound Select mode, the dematrix
function is automatically selected based on the identification
information in the STATUS register. No I2C
interaction is necessary when the broadcasted sound
mode changes (e.g. from mono to stereo).
The demodulator supports the identification check by
switching between mono compatible standards (standards
that have the same FM mono carrier) automatically
and non-audible. If B/G-FM or B/G-NICAM is
selected, the MSP will switch between these standards.
The same action is performed for the standards:
D/K1-FM, D/K2-FM, and D/K-NICAM. Switching
is only done in the absence of any stereo or bilingual
identification. If identification is found, the MSP keeps
the detected standard.
In case of high bit-error rates, the MSP 34x1G automatically
falls back from digital NICAM sound to analog
FM or AM mono.
Table 2–1 summarizes all actions that take place when
Automatic Sound Select is switched on.
To provide more flexibility, the Automatic Sound Select
block prepares four different source channels of
demodulated sound (Fig 2–3). By choosing one of the
four demodulator channels, the preferred sound mode
can be selected for each of the output channels (loudspeaker,
headphone, etc.). This is done by means of
the Source Select registers.
The following source channels of demodulated sound
– “FM/AM” channel: Analog mono sound, stereo if
available. In case of NICAM, analog mono only
(FM or AM mono).
– “Stereo or A/B” channel: Analog or digital mono
sound, stereo if available. In case of bilingual broadcast,
it contains both languages A (left) and B
– “Stereo or A” channel: Analog or digital mono
sound, stereo if available. In case of bilingual broadcast,
it contains language A (on left and right).
– “Stereo or B” channel: Analog or digital mono
sound, stereo if available. In case of bilingual broadcast,
it contains language B (on left and right).
Fig 2–2 shows the source channel assignment of the
demodulated signals in case of manual mode. If manual
mode is required, more information can be found in
the section “Demodulator Source Channels in Manual
Mode” on page 96. Fig 2–3 and Table 2–2 show the
source channel assignment of the demodulated signals
in case of Automatic Sound Select mode for all
Note: The analog primary input channel contains the
signal of the mono FM/AM carrier or the L+R signal of
the MPX carrier. The secondary input channel contains
the signal of the 2nd FM carrier, the L-R signal of the
MPX carrier, or the SAP signal.
2.3. Preprocessing for SCART and
I2S Input Signals
The SCART and I2S inputs need only be adjusted in
level by means of the SCART and I2S prescale registers.
2.4. Source Selection and Output Channel Matrix
The Source Selector makes it possible to distribute all
source signals (one of the demodulator source channels,
SCART, or I2S input) to the desired output channels
(loudspeaker, headphone, etc.). All input and output
signals can be processed simultaneously. Each
source channel is identified by a unique source
For each output channel, the sound mode can be set
to sound A, sound B, stereo, or mono by means of the
output channel matrix.
If Automatic Sound Select is on, the output channel
matrix can stay fixed to stereo (transparent) for
2.5. Audio Baseband Processing
2.5.1. Automatic Volume Correction (AVC)
Different sound sources (e.g. terrestrial channels, SAT
channels, or SCART) fairly often do not have the same
volume level. Advertisements during movies usually
have a higher volume level than the movie itself. This
results in annoying volume changes. The Automatic
Volume Correction (AVC) solves this problem by
equalizing the volume level.
To prevent clipping, the AVC’s gain decreases quickly
in dynamic boost conditions. To suppress oscillation
effects, the gain increases rather slowly for low level
inputs. The decay time is programmable by means of
the AVC register (see page 34).
For input signals ranging from -24 dBr to 0 dBr, the
AVC maintains a fixed output level of -18 dBr. Fig. 2–4
shows the AVC output level versus its input level. For
prescale and volume registers set to 0 dB, a level of
0 dBr corresponds to full scale input/output. This is
– SCART input/output 0 dBr = 2.0 Vrms
– Loudspeaker and Aux output 0 dBr = 1.4 Vrms
2.5.2. Loudspeaker and Headphone Outputs
The following baseband features are implemented in
the loudspeaker and headphone output channels:
bass/treble, loudness, balance, and volume. A square
wave beeper can be added to the loudspeaker and
headphone channel. The loudspeaker channel additionally
performs: equalizer (not simultaneously with
bass/treble), spatial effects, and a subwoofer crossover
2.5.3. Subwoofer Output
The subwoofer signal is created by combining the left
and right channels directly behind the loudness block
using the formula (L+R)/2. Due to the division by 2, the
D/A converter will not be overloaded, even with full
scale input signals. The subwoofer signal is filtered by
a third-order low-pass with programmable corner frequency
followed by a level adjustment. At the loudspeaker
channels, a complementary high-pass filter
can be switched on. Subwoofer and loudspeaker output
use the same volume (Loudspeaker Volume Register).
2.5.4. Quasi-Peak Detector
The quasi-peak readout register can be used to read
out the quasi-peak level of any input source. The feature
is based on following filter time constants:
attack time: 1.3 ms
decay time: 37 ms
2.6. Virtual Surround System Application Tips
2.6.1. Sweet Spot
Good results are only obtained in a rather close area
along the middle axis between the two loudspeakers:
the sweet spot. Moving away from this position
degrades the effect.
For the test at Dolby Labs, it is very important to have
no clipping effects even with worst case signals. That
is, 2 Vrms input signal may not clip. The SCART Input
Prescale register has to be set to values of 19hex
(25dec) or lower (see SCART Input Prescale on page
Test signals: sine sweep with 2 VRMS; L only, R only,
L&R equal phase, L&R anti phase.
Listening tests: Dolby Trailers (train trailer, city trailer,
2.6.3. Loudspeaker Requirements
The loudspeakers used and their positioning inside the
TV set will greatly influence the performance of the virtualizer.
The algorithm works with the direct sound
path. Reflected sound waves reduce the effect. So it’s
most important to have as much direct sound as possible,
compared to indirect sound.
To obtain the approval for a TV set, Dolby Laboratories
require mounting the loudspeakers in front of the set.
Loudspeakers radiating to the side of the TV set will
not produce convincing effects. Good directionality of
the loudspeakers towards the listener is optimal.
The virtualizer was specially developed for implementation
in TV sets. Even for rather small stereo TV's,
sufficient sound effects can be obtained. For small
sets, the loudspeaker placement should be to the side
of the CRT; for large screen sets (or 16:9 sets), mounting
the loudspeakers below the CRT is acceptable
(large separation is preferred, low frequency speakers
should be outmost to avoid cancellation effects). Using
external loudspeakers with a large stereo base will not
create optimal effects.
The loudspeakers should be able to reproduce a wide
frequency range. The most important frequency range
starts from 160 Hz and ranges up to 5 kHz.
Great care has to be taken with systems that use one
common subwoofer: A single loudspeaker cannot
reproduce virtual sound locations. The crossover frequency
must be lower than 120 Hz.
PANASONIC TX-25CK1C/M CHASSIS Z8 TDA9365 series TV signal processor-Teletext decoder with embedded m-Controller
The various versions of theTDA935X/6X/8X series
combine the functions of a TV signal processor together
with a m-Controller and US Closed Caption decoder. Most
versions have a Teletext decoder on board. The Teletext
decoder has an internal RAM memory for 1or 10 page text.
The ICs are intended to be used in economy television
receivers with 90° and 110° picture tubes.
The ICs have supply voltages of 8 V and 3.3 V and they
are mounted in S-DIP envelope with 64 pins.
· Multi-standard vision IF circuit with alignment-free PLL
· Internal (switchable) time-constant for the IF-AGC circuit
· A choice can be made between versions with mono
intercarrier sound FM demodulator and versions with
QSS IF amplifier.
· The mono intercarrier sound versions have a selective
FM-PLL demodulator which can be switched to the
different FM sound frequencies (4.5/5.5/6.0/6.5 MHz).
The quality of this system is such that the external
band-pass filters can be omitted.
· Source selection between ‘internal’ CVBS and external
CVBS or Y/C signals
· Integrated chrominance trap circuit
· Integrated luminance delay line with adjustable delay
· Asymmetrical ‘delay line type’ peaking in the luminance
· Black stretching for non-standard luminance signals
· Integrated chroma band-pass filter with switchable
· Only one reference (12 MHz) crystal required for the
m-Controller, Teletext- and the colour decoder
· PAL/NTSC or multi-standard colour decoder with
automatic search system
· Internal base-band delay line
· RGB control circuit with ‘Continuous Cathode
Calibration’, white point and black level off set
adjustment so that the colour temperature of the dark
and the light parts of the screen can be chosen
· Linear RGB or YUV input with fast blanking for external
RGB/YUV sources. The Text/OSD signals are internally
supplied from the m-Controller/Teletext decoder
· Contrast reduction possibility during mixed-mode of
OSD and Text signals
· Horizontal synchronization with two control loops and
alignment-free horizontal oscillator
· Vertical count-down circuit
· Vertical driver optimized for DC-coupled vertical output
· Horizontal and vertical geometry processing
· Horizontal and vertical zoom function for 16 : 9
· Horizontal parallelogram and bow correction for large
screen picture tubes
· Low-power start-up of the horizontal drive circuit
· 80C51 m-controller core standard instruction set and
· 1 ms machine cycle
· 32 - 128Kx8-bit late programmed ROM
· 3 - 12Kx8-bit Auxiliary RAM (shared with Display and
· Interrupt controller for individual enable/disable with two
· Two 16-bit Timer/Counter registers
· WatchDog timer
· Auxiliary RAM page pointer
· 16-bit Data pointer
· IDLE and Power Down (PD) mode
· 14 bits PWM for Voltage Synthesis Tuning
· 8-bit A/D converter
· 4 pins which can be programmed as general I/O pin,
ADC input or PWM (6-bit) output
· Text memory for 1 or 10 pages
· In the 10 page versions inventory of transmitted Teletext
pages stored in the Transmitted Page Table (TPT) and
Subtitle Page Table (SPT)
· Data Capture for US Closed Caption
· Data Capture for 525/625 line WST, VPS (PDC system
A) and Wide Screen Signalling (WSS) bit decoding
· Automatic selection between 525 WST/625 WST
· Automatic selection between 625 WST/VPS on line 16
· Real-time capture and decoding for WST Teletext in
Hardware, to enable optimized m-processor throughput
· Automatic detection of FASTEXT transmission
· Real-time packet 26 engine in Hardware for processing
accented, G2 and G3 characters
· Signal quality detector for video and WST/VPS data
· Comprehensive teletext language coverage
· Full Field and Vertical Blanking Interval (VBI) data
capture of WST data
· Teletext and Enhanced OSD modes
· Features of level 1.5 WST and US Close Caption
· Serial and Parallel Display Attributes
· Single/Double/Quadruple Width and Height for
· Scrolling of display region
· Variable flash rate controlled by software
· Enhanced display features including overlining,
underlining and italics
· Soft colours using CLUT with 4096 colour palette
· Globally selectable scan lines per row (9/10/13/16) and
character matrix [12x10, 12x13, 12x16 (VxH)]
· Fringing (Shadow) selectable from N-S-E-W direction
· Fringe colour selectable
· Meshing of defined area
· Contrast reduction of defined area
· Special Graphics Characters with two planes, allowing
four colours per character
· 32 software redefinable On-Screen display characters
· 4 WST Character sets (G0/G2) in single device (e.g.
Latin, Cyrillic, Greek, Arabic)
· G1 Mosaic graphics, Limited G3 Line drawing
· WST Character sets and Closed Caption Character set
in single device
FUNCTIONAL DESCRIPTION OF VIDEO PROCESSOR
Vision IF amplifier
The vision IF amplifier can demodulate signals with
positive and negative modulation. The PLL demodulator is
The VCO of the PLL circuit is internal and the frequency is
fixed to the required value by using the clock frequency of
the m-Controller/Teletext decoder as a reference. The
setting of the various frequencies (38, 38.9, 45.75 and
58.75 MHz) can be made via the control bits IFA-IFC in
subaddress 27H. Because of the internal VCO the IF
circuit has a high immunity to EMC interferences.
QSS Sound circuit (QSS versions)
The sound IF amplifier is similar to the vision IF amplifier
and has an external AGC decoupling capacitor.
The single reference QSS mixer is realised by a multiplier.
In this multiplier the SIF signal is converted to the
intercarrier frequency by mixing it with the regenerated
picture carrier from the VCO. The mixer output signal is
supplied to the output via a high-pass filter for attenuation
of the residual video signals. With this system a high
performance hi-fi stereo sound processing can be
The AM sound demodulator is realised by a multiplier. The
modulated sound IF signal is multiplied in phase with the
limited SIF signal. The demodulator output signal is
supplied to the output via a low-pass filter for attenuation
of the carrier harmonics. The AM signal is supplied to the
output (pin 44) via the volume control.
It is possible to get the AM output signal (not controlled on
amplitude) on the QSS intercarrier output. The selection is
made by means of the AM bit in subaddress 29H.
Another possibility is that pin 35 is transferred to external
audio input pin and pin 32 to (non-controlled) AM output
pin. This can be realised by means of the setting the
control bits CMB0 and CMB1 in subaddress 22H.
FM demodulator and audio amplifier (mono versions)
The FM demodulator is realised as narrow-band PLL with
external loop filter, which provides the necessary
selectivity without using an external band-pass filter. To
obtain a good selectivity a linear phase detector and a
constant input signal amplitude are required. For this
reason the intercarrier signal is internally supplied to the
demodulator via a gain controlled amplifier and AGC
circuit. The nominal frequency of the demodulator is tuned
to the required frequency (4.5/5.5/6.0/6.5 MHz) by means
of a calibration circuit which uses the clock frequency of
the m-Controller/Teletext decoder as a reference. The
setting to the wanted frequency is realised by means of the
control bits FMA and FMB in control byte 29H.
When required an external sound band-pass filter can be
inserted in front of the narrow-band PLL. In that case pin
32 has to be switched to sound IF input by means of the
bits SIF (subaddress 21H) and CMB0/CMB1 (subaddress
22H). When the sound IF input is selected the subcarrier
output (90° versions) or AVL function (110° versions) are
From the output status bytes it can be read whether the
PLL frequency is inside or outside the window and whether
the PLL is in lock or not. With this information it is possible
to make an automatic search system for the incoming
sound frequency. This can be realised by means of a
software loop which switches the demodulator to the
various frequencies and then select the frequency on
which a lock condition has been found.
The deemphasis output signal amplitude is independent of
the TV standard and has the same value for a frequency
deviation of ±25 kHz at the 4.5 MHz standard and for a
deviation of ±50 Khz for the other standards.
The audio control circuit contains an audio switch and
volume control. In the mono intercarrier sound versions
the Automatic Volume Levelling (AVL) function can be
activated. The pin to which the external capacitor has to be
connected depends on the IC version. For the 90° types
the capacitor is connected to the EW output pin (pin 20).
For the 110° types a choice must be made between the
AVL function and a sub-carrier output for comb filter
applications. This choice is made via the CBM0 and
CMB1bits (in subaddress 22H). When the AVL is active it
automatically stabilises the audio output signal to a certain
The signal on the deemphasis pin (28) can be supplied to
the SCART connector via a buffer stage. It is also possible
to use this pin as additional audio input. In that case the
internal signal must, of course, be switched off. This can
be realised by means of the sound mute bit (SM in
subaddress 29H). When the IF circuit is switched to
positive modulation the internal signal on the deemphasis
pin is automatically muted.
The video switch has one input for an external CVBS or
Y/C signal. The switch configuration is given in Fig.40. The
selected CVBS signal can be supplied to pin 38, the IF
video output. The selection between both signals is
realised by means of the SVO bit in subaddress 22H.
The video ident circuit can be connected to the incoming
‘internal’ video signal or to the selected signal. This ident
circuit is independent of the synchronisation and can be
used to switch the time-constant of the horizontal PLL
depending on the presence of a video signal (via the VID
bit). In this way a very stable OSD can be realised.
Because of the availability of the Y/C input and the
subcarrier output an external comb-filter can be applied. In
that case an external video switch (or comb-filter with
integrated switch) must be used.
The subcarrier output is combined with a 3-level output
switch (0 V, 4 V and 8 V). The output level and the
availability of the subcarrier signal is controlled by the
CMB1 and CMB0 bits. The output can be used to switch
sound traps etc. It is also possible to use this pin for the
connection of the AVL capacitor, external sound IF input or
as AM output. The possibilities are illustrated in table 1.
The IC contains separator circuits for the horizontal and
vertical sync pulses and a data-slicing circuit which
extracts the digital teletext data from the analog signal.
The horizontal drive signal is obtained from an internal
VCO which is running at a frequency of 25 MHz. This
oscillator is stabilised to this frequency by using a 12 MHz
signal coming from the reference oscillator of the
The horizontal drive is switched on and off via the soft
start/stop procedure. This function is realised by means of
variation of the TON of the horizontal drive pulses. In
addition the horizontal drive circuit has a ‘low-power
The vertical synchronisation is realised by means of a
divider circuit. The vertical ramp generator needs an
external resistor and capacitor. For the vertical drive a
differential output current is available. The outputs must be
DC coupled to the vertical output stage.
In the types which are intended for 90° picture tubes the
following geometry parameters can be adjusted:
· Horizontal shift
· Vertical amplitude
· Vertical slope
· Vertical shift
The types which are intended to be used in combination
with 110° picture tubes have an East-West control circuit
in stead of the AVL function. The additional controls for
these types are:
· EW width
· EW parabola width
· EW upper and lower corner parabola correction
· EW trapezium correction
· Vertical zoom
and in some versions:
· horizontal parallelogram and bow correction.
Chroma and luminance processing
The chroma band-pass and trap circuits (including the
SECAM cloche filter) are realised by means of gyrators
and are tuned to the right frequency by comparing the
tuning frequency with the reference frequency of the
colour decoder. The luminance delay line and the delay
cells for the peaking circuit are also realised with gyrators.
The circuit contains a black stretcher function which
corrects the black level for incoming signals which have a
difference between the black level and the blanking level.
The ICs can decode PAL, NTSC and SECAM signals. The
PAL/NTSC decoder does not need external reference
crystals but has an internal clock generator which is
stabilised to the required frequency by using the 12 MHz
clock signal from the reference oscillator of the
Under bad-signal conditions (e.g. VCR-playback in feature
mode), it may occur that the colour killer is activated
although the colour PLL is still in lock. When this killing
action is not wanted it is possible to overrule the colour
killer by forcing the colour decoder to the required standard
and to activate the FCO-bit (Forced Colour On) in
The Automatic Colour Limiting (ACL) circuit (switchable
via the ACL bit in subaddress 20H) prevents that
oversaturation occurs when signals with a high
chroma-to-burst ratio are received. The ACL circuit is
designed such that it only reduces the chroma signal and
not the burst signal. This has the advantage that the colour
sensitivity is not affected by this function.
The SECAM decoder contains an auto-calibrating PLL
demodulator which has two references, viz: the divided 12
MHz reference frequency (obtained from the m-Controller)
which is used to tune the PLL to the desired free-running
frequency and the bandgap reference to obtain the correct
absolute value of the output signal. The VCO of the PLL is
calibrated during each vertical blanking period, when the
IC is in search or SECAM mode.
The base-band delay line (TDA 4665 function) is
integrated. This delay line is also active during NTSC to
obtain a good suppression of cross colour effects. The
demodulated colour difference signals are internally
supplied to the delay line.
RGB output circuit and black-current stabilization
In the RGB control circuit the signal is controlled on
contrast, brightness and saturation. The ICs have a linear
input for external RGB signals. It is possible to use this
input for the insertion of YUV signals. Switching between
RGB and YUV can be realised via the YUV-bit in
subaddress 2BH. The signals for OSD and text are
internally supplied to the control circuit. The output signal
has an amplitude of about 2 Volts black-to-white at
nominal input signals and nominal settings of the various
To obtain an accurate biasing of the picture tube the
‘Continuous Cathode Calibration’ system has been
included in these ICs. A black level off set can be made
with respect to the level which is generated by the black
current stabilization system. In this way different colour
temperatures can be obtained for the bright and the dark
part of the picture.
The black current stabilization system checks the output
level of the 3 channels and indicates whether the black
level of the highest output is in a certain window (WBC-bit)
or below or above this window (HBC-bit). This indication
can be read from the status byte 01 and can be used for
automatic adjustment of the Vg2 voltage during the
production of the TV receiver.
During switch-off of the TV receiver a fixed beam current
is generated by the black current control circuit. This
current ensures that the picture tube capacitance is
discharged. During the switch-off period the vertical
deflection is placed in an overscan position so that the
discharge is not visible on the screen.
The CPU communicates with the peripheral functions
using Special function Registers (SFRs) which are
addressed as RAM locations. The registers for the
Teletext decoder appear as normal SFRs in the
m-Controller memory map and are written to these
functions by using a serial bus. This bus is controlled by
dedicated hardware which uses a simple handshake
system for software synchronisation.
For compatibility reasons and possible re-use of software
blocks, the I2C-bus control for the TV processor is
organised as in the stand-alone TV signal processors. The
TV processor registers cannot be read, so when the
content of these registers is needed in the software, a copy
should be stored in Auxiliary RAM or Non Volatile RAM.
1. When the 3.3 V supply is present and the m-Controller is active a ‘low-power start-up’ mode can be activated. When
all sub-address bytes have been sent and the POR and XPR flags have been cleared the horizontal output can be
switched-on via the STB-bit (subaddress 24H). In this condition the horizontal drive signal has the nominal TOFF and
the TON grows gradually from zero to the nominal value. As soon as the 8 V supply is present the switch-on procedure
(e.g. closing of the second loop) is continued.
2. On set AGC.
3. This parameter is not tested during production and is just given as application information for the designer of the
4. Loop bandwidth BL = 60 kHz (natural frequency fN = 15 kHz; damping factor d = 2; calculated with top sync level as
FPLL input signal level).
5. The IF-PLL demodulator uses an internal VCO (no external LC-circuit required) which is calibrated by means of a
digital control circuit which uses the clock frequency of the m-Controller as a reference. The required IF frequency for
the various standards is set via the IFA-IFC bits in subaddress 27H. When the system is locked the resulting IF
frequency is very accurate with a deviation from the nominal value of less than 25 kHz.
6. This parameter is not tested during production but is guaranteed by the design and qualified by means of matrix
batches which are made in the pilot production period.
7. Measured at 10 mV (RMS) top sync input signal.
8. Via this pin (38) both the demodulated IF signal and the selected CVBS (or Y+C) signal can be supplied to the output.
The selection between both signals is realised by means of the SVO bit in subaddress 22H.
9. So called projected zero point, i.e. with switched demodulator.
10. Measured in accordance with the test line given in Fig.49. For the differential phase test the peak white setting is
reduced to 87%.
The differential gain is expressed as a percentage of the difference in peak amplitudes between the largest and
smallest value relative to the subcarrier amplitude at blanking level.
The phase difference is defined as the difference in degrees between the largest and smallest phase angle.
Adjustment of geometry control parameters
The deflection processor offers 5 control parameters for
picture alignment, viz:
· vertical amplitude
· vertical slope
· vertical shift
· horizontal shift.
The 110° types offer in addition:
· EW width
· EW parabola width
· EW upper/lower corner parabola
· EW trapezium correction.
· Vertical zoom
· Horizontal parallelogram and bow correction for some
versions in the range
It is important to notice that the ICs are designed for use
with a DC-coupled vertical deflection stage. This is the
reason why a vertical linearity alignment is not necessary
(and therefore not available).
For a particular combination of picture tube type, vertical
output stage and EW output stage it is determined which
are the required values for the settings of S-correction,EW
parabola/width ratio and EW corner/parabola ratio. These
parameters can be preset via the I2C-bus, and do not need
any additional adjustment. The rest of the parameters are
preset with the mid-value of their control range (i.e. 1FH),
or with the values obtained by previous TV-set
The vertical shift control is meant for compensation of
off sets in the external vertical output stage or in the picture
tube. It can be shown that without compensation these
off sets will result in a certain linearity error, especially with
picture tubes that need large S-correction. The total
linearity error is in first order approximation proportional to
the value of the off set, and to the square of the
S-correction needed. The necessity to use the vertical shift
alignment depends on the expected off sets in vertical
output stage and picture tube, on the required value of the
S-correction, and on the demands upon vertical linearity.
For adjustment of the vertical shift and vertical slope
independent of each other, a special service blanking
mode can be entered by setting the SBL bit HIGH. In this
mode the RGB-outputs are blanked during the second half
of the picture. There are 2 different methods for alignment
of the picture in vertical direction. Both methods make use
of the service blanking mode.
The first method is recommended for picture tubes that
have a marking for the middle of the screen. With the
vertical shift control the last line of the visible picture is
positioned exactly in the middle of the screen. After this
adjustment the vertical shift should not be changed. The
top of the picture is placed by adjustment of the vertical
amplitude, and the bottom by adjustment of the vertical
The second method is recommended for picture tubes that
have no marking for the middle of the screen. For this
method a video signal is required in which the middle of the
picture is indicated (e.g. the white line in the circle test
pattern). With the vertical slope control the beginning of the
blanking is positioned exactly on the middle of the picture.
Then the top and bottom of the picture are placed
symmetrical with respect to the middle of the screen by
adjustment of the vertical amplitude and vertical shift.
After this adjustment the vertical shift has the right setting
and should not be changed.
If the vertical shift alignment is not required VSH should be
set to its mid-value (i.e. VSH = 1F). Then the top of the
picture is placed by adjustment of the vertical amplitude
and the bottom by adjustment of the vertical slope. After
the vertical picture alignment the picture is positioned in
the horizontal direction by adjustment of the EW width and
the horizontal shift. Finally (if necessary) the left- and
right-hand sides of the picture are aligned in parallel by
adjusting the EW trapezium control.
To obtain the full range of the vertical zoom function the
adjustment of the vertical geometry should be carried out
at a nominal setting of the zoom DAC at position 19 HEX.