TV set switched off ....................................................................................................................................................... 2
2. SMALL SIGNAL PART WITH STV2248 .................................................................................................................... 3
2.1 Vision IF amplifier ................................................................................................................................................... 3
2.3 FM demodulator and audio amplifier (mono versions) ......................................................................................... 3
2.4 Video switch ........................................................................................................................................................... 3
DO NOT CHANGE ANY MODULE UNLESS THE SET IS SWITCHED OFF
The mains supply part of the switch mode power supply’s transformer is live.
Use an isolating transformer.
The receiver complies with the safety requirements.
SAFETY PRECAUTIONS:
The service of this TV set must be carried out by qualified persons only. Components marked with the warning symbol
on the circuit diagram are critical for safety and must only be replaced with an identical component.
- Power resistor and fused resistors must be mounted in an identical manner to the original component.
- When servicing this TV, check that the EHT does not exceed 26kV.
TV set switched off:
Make short-circuit between HV-CRT clip and CRT ground layer.
Short C809 before changing IC800 and IC801 or other components in primary side of the SMPS part.
Measurements:
Voltage readings and oscilloscope traces are measured under the following conditions:
Antenna signal’s level is 60dB at the color bar pattern from the TV pattern generator. (100% white, 75% color saturation)
Brightness, contrast, and color are adjusted for normal picture performance.
Mains supply, 220VAC, 50Hz.
PERI-TV SOCKET
SCART 1 (SC050)SCART 2 (SC051)
1Audio right output0.5Vrms / 1K1Audio right output0.5Vrms / 1K
2Audio right input0.5Vrms / 10K2Audio right input0.5Vrms / 10K
3Audio left output0.5Vrms / 1K3Audio left output0.5Vrms / 1K
4Ground AF4Ground AF
5Ground Blue5Ground Blue
6Audio left input0.5Vrms / 10K6Audio left input0.5Vrms / 10K
7Blue input0.7Vpp / 75ohm7Blue input0.7Vpp / 75ohm
8AV switching input 0-12VDC /10K8AV switching input0-12VDC /10K
9Ground Green9Ground Green
10-10 11Green input0.7Vpp / 75ohm11 12-12 13 Ground Red13 Ground Red
14 Ground Blanking14 Ground Blanking
15 Red input0.7Vpp / 75ohm15 16 Blanking input0-0.4VDC, 1-3VDC / 75ohm16 17 Ground CVBS output17 Ground CVBS output
18 Ground CVBS input18 Ground CVBS input
19CVBS output1Vpp / 75ohm19 CVBS output1Vpp / 75ohm
20CVBS input1Vpp / 75ohm20 CVBS input1Vpp / 75ohm
21 Ground21 Ground
1. INTRODUCTION
11AK30 is a 90° chassis capable of driving 20”/21” tubes at the appropriate currents. The chassis is capable of operating
in PAL, SECAM and NTSC standards. The sound system is capable of giving 5 watts RMS output into a load of 8 ohms.
One page, 7 page SIMPLETEXT, TOPTEXT, FASTTEXT and US Closed Caption is also provided. The chassis is equipped
with a double-deck 42 pin Scart connector.
2
2. SMALL SIGNAL PART WITH STV2248:
STV2248 video processor is essential for realizing all small signal functions for a color TV receiver.
2.1 Vision IF amplifier3
The vision IF amplifier can demodulate signals with positive and negative modulation. The PLL demodulator is completely
alignment-free. Although the VCO (Toko-coil) of the PLL circuit is external, yet the frequency is fixed to the required value
by the original manufacturer thus the Toko-coil does not need to be adjusted manually. The setting of the various
frequencies (38.9 or 45.75 MHz) can be made via changing the coil itself.
2.2 QSS Sound circuit (QSS versions)
The sound IF amplifier is similar to the vision IF amplifier and has an external AGC de-coupling capacitor. The single
reference QSS mixer is realised by a multiplier. In this multiplier the SIF signal is converted to the inter-carrier 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 achieved. 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 via the volume control.
2.3. AM DEMODULA T OR
The AM demodulated signal results from multiplying the input signal by itself, it is available on AM/FM output.
2.3 FM demodulator and audio amplifier (mono versions):
The FM demodulator is realized 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 constant input signal
amplitude are required. For this reason the inter-carrier 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 that uses the clock frequency of the -controller/Teletext decoder as a
reference. The setting to the wanted frequency is realized by means of the software. 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 is realized by means of a software loop that
alternate the demodulator to various frequencies, then select the frequency on which a lock condition has been found.
De-emphasis 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. When the IF circuit is
switched to positive modulation the internal signal on de-emphasis pin is automatically muted. The audio control circuit
contains an audio switch and volume control. In the mono inter-carrier sound versions the Automatic Volume Leveling
(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). When the AVL is active it automatically
stabilizes the audio output signal to a certain level.
2.4 Video switching
The video processor (STV2248C) has three CVBS inputs and two RGB inputs. The first CVBS input is used for external
CVBS from SCART 1, the second is used for either CVBS or Y/C from either SCART2 or BAV/FAV, and the third one is used
for internal video. The selection between both external video inputs signals is realized by means of software and hardware
switches.
2.5 Synchronization circuit
The video processor (STV224X) performs the horizontal and vertical processing. The external horizontal deflection circuit
is controlled via the Horizontal output pulse (HOUT). The vertical scanning is performed through an external ramp
generator and a vertical power amplifier IC controlled by the Vertical output pulse (VOUT).
The main components of the deflection circuit are:
• PLL1: the first phase locked loop that locks the internal line frequency reference on the CVBS input signal.
It is composed of an integrated VCO (12 MHz) that requires the chroma Reference frequency (4.43MHz or 3.58MHz
crystal oscillator reference signal), a divider by 768, a line decoder, and a phase comparator.
• PLL2: The second phase locked loop that controls the phase of the horizontal output (Compensation of horizontal
deflection transistor storage time variation). Also the horizontal position adjustment is also performed in PLL2.
• A vertical pulse extractor.
• A vertical countdown system to generate all vertical windows (vertical synchronization window, frame blanking pulses,
50/60Hz identification window...).
• Automatic identification of 50/60Hz scanning.
• PLL1 time constant control.
• Noise detector, video identification circuits, and horizontal coincidence detector.
• Vertical output stage including de-interlace function, vertical position control.
• Vertical amplitude control voltage output (combined with chroma reference output and Xtal 1 indication).
3
2.6 Chroma and luminance processing:
The chroma decoder is able to demodulate PAL, NTSC and SECAM signals. The decoder dedicated to PAL and NTSC
sub-carrier is based on a synchronous demodulator, and an Xtal PLL locked on the phase reference signal (burst).
The SECAM demodulation is based on a PLL with automatic calibration loop.
The color standard identification is based on the burst recognition.
Automatic and forced modes can be selected through the I2C bus.
NTSC tint, and auto flesh are controlled through I2C bus.
Xtal PLL can handle up to 3 crystals to work in PAL M, PAL N and NTSC M for South America.
ACC an ACC overload control the chroma sub-carrier amplitude within 26dB range. Both
ACC s are based on digital systems and do not need external capacitor.
All chroma filters are fully integrated and tuned via a PLL locked on Xtal VCO signal.
A second PLL is used for accurate fine-tuning of the SECAM bell filter. This tuning is achieved during the frame blanking.
An external capacitor memorizes the bell filter tuning voltage.
A base-band chroma delay-line rebuilds the missing color line in SECAM and removes transmission phase errors in PAL.
The base-band chroma delay line is clocked with 6MHz signal provided by the horizontal scanning VCO.
The luminance processor is composed of a chroma trap filter, a luminance delay line, a peaking function with noise coring
feature, a black stretch circuit.
Trap filter and luminance delay lines are achieved with the use of bi-quad integrated filters, auto-aligned via a master filter
phase locked loop.
2.7 RGB output circuit:
The video processor performs the R, G, B processing.
There are three sources:
1. Y,U,V inputs (coming from luma part (Y output), and chroma decoder outputs (R-Y, B-Y outputs).
2. External R,G,B inputs from SCART (converted internally in Y,U,V), with also the possibility to input YUV signals from
a DVD player, (YUV specification is Y=0.7 V PP , U= 0.7 V PP , V = 0.7V PP for 100% color bar).
3. Internal R,G,B inputs (for OSD and Teletext display)
The main functions of the video part are:
Y,U,V inputs with integrated clamp loop, allowing a DC link with YUV outputs,
External RGB inputs (RGB to YUV conversion), or direct YUV inputs,
Y,U,V switches,
Contrast, saturation, brightness controls,
YUV to RGB matrix,
OSD RGB input stages (with contrast control),
RGB switches,
APR function,
DC adjustment of red and green channels,
Drive adjustments (R, G, B gain),
Digital automatic cut-off loop control,
Manual cut-off capability with I2C adjustments,
Half tone, oversize blanking, external insertion detection, blue screen,
Blanking control and RGB output stages.
2.8 -Controller
The ST92195 is the micro-controller, which is required for a color TV receiver. ST92195D1 is the version with one page
Teletext and ST92195D7 is the one with 7 page Teletext. The IC has the supply voltages of 5 V and they are mounted in
PSDIP package with 56 pins.
-Controller has the following features
Display of the program number, channel number, TV Standard, analogue values, sleep timer, parental control and
mute is done by OSD
Single LED for standby and on mode indication
System configuration with service mode
3 level logic output for SECAM and Tuner band switching
4
3. TUNER
Either a PLL or a VST tuner is used as a tuner.
UV1316 (VHF/UHF) is used as a PLL tuner. For only PALM/N, NTSC M applications UV 1336 is used as the
PLL tuner. UV 1315 (VHF/UHF) is used as a VST Tuner.
Channel coverage of UV1316:
OFF-AIR CHANNELSCABLE CHANNELS
BAND
FREQUENCY
RANGE (MHz)
CHANNELSCHANNELS
Low Band E2 to C 48.25 to 82.25 (1) S01 to S08 69.25 to 154.25
Mid Band E5 to E12 175.25 to 224.25 S09 to S38 161.25 to 439.25
High Band E21 to E69 471.25 to 855.25 (2) S39 to S41 447.25 to 463.25
(1). Enough margin is available to tune down to 45.25 MHz.
(2). Enough margin is available to tune up to 863.25 MHz.
Low Band 2 to D 55.25 to 139.25
Mid Band E to PP 145.25 to 391.25
High Band QQQ to 69 397.25 to 801.25
Noise is typically 6dB for all channels. Gain is minimum 38dB and maximum 50dB for all channels.
Channel Coverage of UV1315:
OFF-AIR CHANNELSCABLE CHANNELS
BAND
FREQUENCY
RANGE (MHz)
CHANNELSCHANNELS
FREQUENCY
RANGE (MHz)
Low Band E2 to C 48.25 to 82.25 (1) S01 to S08 69.25 to 168.25
Mid Band E5 to E12 175.25 to 224.25 S11 to S39 231.25 to 447.25
High Band E21 to E69 471.25 to 855.25 (2) S40 to S41 455.25 to 463.25
(1). Enough margin is available to tune down to 45.25 MHz.
(2). Enough margin is available to tune up to 863.25 MHz.
NoiseTyp.Max. GainMin.Typ.Max.
Low band6dB9dBAll Channels38dB44dB50dB
Mid band6dB10dBGain Taper8dB
High band6dB11dB(off-air channels)
4. DIGITAL TV SOUND PROCESSOR MSP34X0
The MSP 34x0D is designed to perform demodulation of FM or AM-Mono TV sound. Alternatively, two-carrier FM systems
according to the German or Korean terrestrial specs or the satellite specs can be processed with the MSP 34x0D. Digital
demodulation and decoding of NICAM-coded TV stereo sound, is done only by the MSP 3410. The MSP 34x0D offers a
powerful feature to calculate the carrier field strength which can be used for automatic standard detection (terrestrial) and
search algorithms (satellite).
5. SOUND OUTPUT ST AGE TDA7266L/TDA7266
TDA7266L is used as the AF output amplifier for mono applications. It is supplied by +12VDC coming from a separate
winding in the SMPS transformer. An output power of 5.5W (THD=0.5%) can be delivered into an 8ohm load.
TDA7266 is used as the AF output amplifier for stereo applications. It is supplied by
+12VDC coming from a separate winding in the SMPS transformer. An output power of 2*5.5W (THD=0.5%) can be delivered
into an 8ohm load.
5
6. VERTICAL OUTPUT STAGE WITH TDA8174A
The TDA8174A is a power amplifier circuit for use in 90° and 110° colour deflection systems for 25 to 200 Hz field
frequencies, and for 4 : 3 and 16 : 9 picture tubes.
7. VIDEO OUTPUT AMPLIFIER STV5112
The STV5112 consists of three monolithic video output amplifiers. The amplifier can be seen as an operational amplifier
with negative feedback. The advantage of negative feedback is that the amplifier characteristics do not play an important
role up to certain frequencies. The internal flash diodes protect the amplifiers against flash over in the picture tube.
The only protections required at the cathode outputs are a flash resistor and a spark gap.
Furthermore, the device has a high voltage power supply (VDD) and a low voltage one (VCC).
8. POWER SUPPLY (SMPS)
The DC voltages required at various parts of the chassis are provided by an SMPS transformer controlled by the IC
MC44608 which is designed for driving, controlling and protecting switching transistor of SMPS. The transformer produces
115V for FBT input, ±14V for audio output IC, S+3.3, S+5V and 8V for ST92195.
9. POWER FACTOR CORRECTION
Passive components are used for the solution of power factor correction.
10. SERIAL ACCESS CMOS 8K EEPROM 24C08
The 24C08 is a 8Kbit electrically erasable programmable memory (EEPROM), organized as 4 blocks of 256*08 bits.The
memory is compatible with the I²C standard, two wire serial interface which uses a bi-directional data bus and serial clock.
11. CLASS AB STEREO HEADPHONE DRIVER TDA1308
The TDA1308 is an integrated class AB stereo headphone driver contained in a DIP8 plastic package
The ST92195 is a member of the ST9+ family of micro-controllers, completely developed and produced by SGSTHOMSON Microelectronics using a proprietary n-well HCMOS process. The nucleus of the ST92195 is the advanced
Core, which includes the Central Processing Unit (CPU), the ALU, the Register File and the interrupt controller. The Core
has independent memory and register buses to add to the efficiency of the code. A set of on-chip peripherals form a
complete sys-tem for TV set and VCR applications:
• Voltage Synthesis
• VPS/WSS Slicer
• Teletext Slicer
• Teletext Display RAM
• OSD
Additional peripherals include a watchdog timer, a serial peripheral interface (SPI), a 16-bit timer and an A/D converter.
u-CONTROLLER VERSİON TABLE
FEATUREDESCRIPTION
NO TXT MONOIC ST92195C 48K SW-A
NO TXT MONO
1 P MONO
1 P MONO / STR
7 P MONO/STR/WSS
1 P MONO/STR/APS/WSS
IC ST92185B SW-B
IC ST92195C 48K SW-D
IC ST92195C 48K SW-E
IC ST92195C 64K SW-F
IC ST92195C 64K SW-G
7
STV224X Video processor:
The STV2246/2247/2248 are fully bus controlled ICs for TV including PIF, SIF, luma, Chroma and deflection processing.
Used with a vertical frame booster (TDA1771 or TDA8174 for 90° chassis, STV9306 for 110° chassis), they allow the
design of multi-standard (BGDKIMNLL, PAL/ SECAM/NTSC) sets with very few external components and no manual
adjustments.
VIDEO PROCESSOR IC TABLE
UV1315, UV1316, UV1336
General description of UV1315:
BAND
VIDEO IC
Low Band 0 V 0 V +5V
Mid Band 0 V +5V 0 V
STV 2246
High Band +5V 0 V 0 V
STV 2247
STV 2248OKOK
PIN 3PIN 3PIN 3
AUDIO STEREOPALSECAM NTSC
-
OK
-
OKOKOK
OKOKOKOK
-
OK
-
The UV1315 tuner belongs to the UV 1300 family of tuners, which are designed to meet a wide range of applications. It is a
combined VHF, UHF tuner suitable for CCIR systems B/G, H, L, L’, I and I’.
Features of UV1315:
•Member of the UV1300 family small sized UHF/VHF tuners
•Systems CCIR:B/G, H, L, L’, I and I’; OIRT:D/K
•Voltage synthesized tuning (VST)
•Off-air channels, S-cable channels and Hyper-band
•Standardized mechanical dimensions and pinning
PINNINGPIN V ALUE
1. Gain control voltage (AGC): 4.0V, Max:4.5V
2. Tuning voltage
3. High band switch: 5V, Min:4.75V, Max:5.5V
4. Mid band switch: 5V, Min:4.75V, Max:5.5V
5. Low band switch: 5V, Min:4.75V, Max:5.5V
6. Supply voltage: 5V, Min:4.75V, Max:5.5V
7. Not connected
8. Not connected
9. Not connected
10.Symmetrical IF output 1
11. Symmetrical IF output 2
Band switching table:
8
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