Saturday, April 27, 2019

TH L39EM5D – Panasonic LCD TV – how to enter the service mode, adjustments, Power board voltages and schematic


Power LED blinking timing chart - Chassis: KM18, Destination: India
How to enter into service mode
While pressing Volume (-) button of the main unit, press (INFO) button of the remote control three times within 2 seconds.
Contents of the adjustment mode
·         Value shown as a hexadecimal number.
·         Preset value differs depending on models.
·         After entering the adjustment mode, take note of the value in each item before starting adjustment.


To exit the service mode, off the power with the power button on the main unit, or the power button on the remote control.
SRV Tool
To access this tool:
Select the (SRV-Tool) in service mode.
Press OK button on the remote control.
To display the SOS history
SOS history (number of LED blinking) indication.
From the left side; last SOS, before Last, three occurrence before, 2nd occurrence after shipment, 1st occurrence after shipment.
This indication except 2nd and the 1st occurrence after shipment will be cleared by [self-check indication and forced to factory shipment setting]
Power on time count
To display the Time count menu, highlight position, and then press Mute for 3 seconds.
Time: cumulative power On time, indicated hour, minute be decimal.
Count: number of ON times by decimal.
This indication will not be cleared by either of the self checks or by other command.
To exit, disconnect the AC chord fro wall outlet.
Self-check mode
Press the Menu button n the remote control, and the Volume Down button on the SCD panel.
Press the ON/Off button on the panel to exit.
Hotel mode adjustment
In order to display the Hotel mode setup menu, enter the following command; within 2 seconds.
TV: VOL DN +
Remote: Input 3 times.
To exit the hotel mode setup menu, disconnect AC power cord from the wall socket.
To check the IIC bus lines
Self check indication only:
Produce TV reception screen, and while pressing Volume[-] button on the main unit, press [Ok] button on the remote control  for more than 3 seconds.
Self-check indication and forced to factory shipment setting:
Produce TV reception screen, and while pressing [Volume (-)] button on the main unit, press [Menu] button on the remote control for more than 3 seconds.
Disconnect the AC cord from the wall socket to Exit.
Power LED blinking timing chart
When an abnormality occurs, the protection circuit will operate and the reset the unit to stand by mode.  During this time, the defective block can be identified by the number of blinking times of the power LED on the front panel of the unit.
Voltages of A and P boards and the schematic of P-Board
Power board-TNP4G532AA – schematic

Thursday, April 11, 2019

24PHG4032 – Philips LCD TV – how to enter the service mode, software update, SMPS schematic


TPM17.5L LA- Chassis, MTK5561 – Platform, 24PHG4032/77 – Model
Display resolution
640 x 480 - 60Hz
800 x 600 - 60Hz
1024 x 768 - 60Hz
1360 x 768 - 60Hz
Video formats
Resolution — Refresh rate
480i - 60Hz
 480p - 60Hz
 576i - 50Hz
 576p - 50Hz
 720p - 50Hz
60Hz
 1080i - 50Hz
, 60Hz
 1080p - 24Hz
25Hz30Hz50Hz, 60Hz
Picture / Display
 Display type: - LED backlight HD
 Diagonal size: - 59.8 cm / 24 inches
 Aspect ratio: 16:9 (widescreen)
 Panel resolution: - 1360x768p @60Hz
 Picture enhancement: Digital Crystal Clear
 Picture Performance Index (PPI): 240
Service Modes
The Service Mode feature is split into following parts
Factory Mode
Customer Service Mode (CSM).
SAM and the Factory mode offer features, which can be used by the Service engineer to repair/align a TV set.
The CSM is a Service Mode that can be enabled by the consumer. The CSM displays diagnosis information, which the customer can forward to the dealer or call centre.
 In CSM mode, “CSM”, is displayed in the top right corner of the screen. The information provided in CSM and the purpose of CSM is to:
Increase the home repair hit rate.
Decrease the number of nuisance calls.
Solve customers’ problem without home visit.
Note: For the new model range, a new remote control (RC) is used with some renamed buttons. This has an impact on the activation of the Service modes. 
For instance the old “MENU” button is now called “HOME” (or is indicated by a “house” icon).
Factory mode
To perform extended alignments.
How to Activate the Factory mode
To activate the Factory mode, use the following method:
Press the following key sequence on the remote control transmitter: from the “menu/home” press “1999”, directly followed by the “Back/Return” button. Do not allow the display to time out between entries while keying the sequence.
After entering the Factory mode,  can see many items displayed, use the UP/DOWN keys to display the next/previous menu items
How to Exit the Factory mode
Use one of the following methods:
Select EXIT_FACTORY from the menu and press the “OK” button.
Note: When the TV is switched “off” by a power interrupt, or normal switch to “stand-by” while in the factory mode, the TV will show up in “normal operation mode” as soon as the power is supplied again. The error buffer will not be cleared.
Customer Service Mode (CSM)
The Customer Service Mode shows error codes and information on the TVs operation settings.The call centre can instruct the customer (by telephone) to enter CSM in order to identify the status of the set.This helps the call centre to diagnose problems and failures in the TV set before making a service call.
The CSM is a read-only mode; therefore, modifications are not possible in this mode.
Ignore “Service unfriendly modes”.
Line number for every line (to make CSM language independent).
Set the screen mode to full screen (all contents on screen is visible).
After leaving the Customer Service Mode, the original settings are restored.
Possibility to use “CH+” or “CH-” for channel surfing, or enter the specific channel number on the RC.
How to Activate CSM
To activate CSM, press the following key sequence on a standard remote control transmitter: “456987” (do not allow the display to time out between entries while keying the sequence). After entering the Customer Service Mode, the following items are displayed. use the Right/Left keys to display the next/previous menu items
Note: Activation of the CSM is only possible if there is no (user) menu on the screen.
How to Navigate
By means of the “CURSOR-DOWN/UP” knob (or the scroll wheel) on the RC-transmitter, can be navigated through the menus.
How to Exit CSM
To exit CSM, use one of the following methods.
Press the MENU/HOME button on the remote control transmitter.
Press the POWER button on the remote control transmitter.
Press the POWER button on the television set.
Software Upgrading
The following update is for .bin file.
1. Rename the file to “Usb_update.bin”
2. Prepare a USB memory.
3. Copy the software to USB flash disk(root directory).
4. Switch off the TV and Insert the USB memory stick that contains the software update files in one of the TV’s USB 2.0 ports.
5. Switch on the TV. The TV will detect the USB memory stick automatically.
6. When the TV software is updated, the TV will turn on again automatically. Remove the USB flash drive.
7. We can enter in CSM or Factory mode to check the current software version.
Check the SW version
1. After burning software, TV will restart.
2. Press “Menu+1999+back”, enter Factory mode to check if the software version is correct
Caution: Please make sure that software upgrade is finished before unplug the USB and AC power.
Power Supply Unit
 Philips LCD TV power supplies are a black box for Service. When defective, a new board must be ordered and the defective one must be returned, unless the main fuse of the board is broken. Always replace a defective fuse with one with the correct specifications. This part is available in the regular market.
Consult the Philips Service web portal for the order codes of the boards.
Important delta’s with the platform are:
New power architecture for LED backlight
“Boost”-signal is now a PWM-signal + continuous variable
The control signals are
 PS-ON
 Lamp “on/off”
 DIM (PWM) (not for PSDL)
No detailed information is available because of design protection issues.
 +12 output (on-mode)
 +12V_audio (audio AMP power)
 Output to the display; in case of
- IPB: High voltage to the LCD panel
- PSL and PSLS (LED-driver outputs)
- PSDL (high frequent) AC-current.
Diversity
The diversity in power supply units is mainly determined by the diversity in displays.
The following displays can be distinguished:
 CCFL/EEFL backlight: power panel is conventional IPB
 LED backlight:
- side-view LED without scanning: PSL power panel
- side-view LED with scanning: PSLS power panel
- direct-view LED without 2D-dimming: PSL power panel
- direct-view LED with 2D-dimming: PSDL power panel.
PSL stands for Power Supply with integrated LED-drivers.
PSLS stands for a Power Supply with integrated LED-drivers with added Scanning functionality (added microcontroller).
PSDL stands for a Power Supply for Direct-view LED backlight with 2D-dimming.
DC/DC Converters
The on-board DC/DC converters deliver the following voltages(depending on set execution):
 PVDD from the power 12V_AMP for the AUDIO AMP.
 3V3SB, permanent voltage for the Stand-by controller, LED/IR, keyborad receiver and controls.
 +12V, input from the power supply for the panel common(active mode)
 +12V, input from the power supply for the AMP
 DDRV supply voltage for DDR
 TUNER3.3V, supply voltage for tuner
 +5V_SW, input intermediate supply voltage for the USB Power
 3V3SB, from the power supply for the scaler IC MT5561
 DVDD3V3, +1V2,clean voltage for Demodulator IC channel decoder.
Electro help - Service Modes, Circuit Diagrams, Firmware Update procedure, Disassemble procedure, Universal remote control set-up codes, Troubleshooting and more....

Friday, April 05, 2019

Sharp 21LT 45SES how to enter the service mode, default data values, and all details of Vestel 11AK44 Chassis

PAL B/G / SECAM L/L’, B/G, D/K SYSTEM COLOUR TELEVISION: AK-44 Chassis
Vestal11AK44 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 4 watts RMS output into a load of 16 ohms.
The chassis in this receiver is partially hot. Use an isolation transformer between the line cord plug and power receptacle, when servicing this chassis.
White Level
Apply the rated voltage at the rated frequency to the TV set, while it is receiving full white pattern RF signal of 60 dB/µV from its RF input via the pattern generator.
Turn all picture controls to maximum value. Measure the colour temperatures at the center of the screen by using the colour analyzer.
X=0.290 ± 0.015 Y=0.300 ± 0.015
It is important that the static charge is removed from the high voltage system when carrying out work on the receiver. This can be achieved by connecting a 10K resistor (with a suitably insulated lead) from the CRT cavity connector to the CRT ground tag. This must be carried out with the AC supply disconnected from the receiver.
DO NOT increase the EHT to more than 29.5 KV, (at a instantaneous beam current of 1150 µA
This level has been preset in the factory. Always check that this level has not been exceeded after carrying out any repair on the receiver.
To update the Technical Information
Web site: https://www.vestelservice.com
Select: Technical Support
Login: 101278
Password: SHPII278
By this access you can consult the latest schematic diagram or request the Parts Listing of a concrete Production Date / Serial Number.
PERI-TV SOCKET connections detail
Vision IF amplifier
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 33,8 MHz) can be made via changing the coil itself.
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 realized 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.
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 µ-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 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). When the AVL is active it automatically stabilises the audio output signal to a certain level.
Synchronisation 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 (4.43 MHz or 3.58 MHz 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, 50/60 Hz identification window...).
• Automatic identification of 50/60 Hz 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).
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 ACCs 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 6 MHz 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.
µ-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 voltage of 5 V and they are mounted in PSDIP package with 56 pins.
µ-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 stand-by and on mode indication
- System configuration with service mode
- 3 level logic output for SECAM and Tuner band switching
IC 501 controls all the functions of the receiver operated by the remote control and the front panel customer controls. It produces the on screen graphics, operates tuning, customers controls and engineering controls, and also incorporates all of the Teletext functions. It also controls the video processor, the audio processor, and the tuner. The circuits just mentioned are controlled via the I²C bus. Also IC501 controls the video source switching, vertical position adjustment and the vertical linearity adjustment via its ports.
An external 8K EEPROM is used by the micro. The EEPROM comes fully programmed. The main clock oscillator is 4.0 MHz crystal X501 on pins 50 and 51. Reset is provided on pin 2 via Q504. On switching on pin 2 becomes high and the controller gets reset which stays valid till a low signal comes on that pin.
Controls
Command information from the infrared remote controller is fed through the sensor IC502 to pin 1 of the microprocessor. Operation of the customer front panel keys is detected by pin 8 that is an ADC (analogue to digital converter). Pressing a switch will connect the 5V to the ground through a particular resistor that determines the value of the voltage on pin8 at that instant. This obtained value is comprehended by the micro and the corresponding operation is performed.
IC501 automatically switches from TV mode to AV1 by detecting the signal from or pin8 at the Scart connector, through it 56 pins.
Teletext
The microprocessor IC501 performs all of the Teletext functions internally. The Composite blanking video and Sync signal (CBVS) is input to pin 33 of the micro from pin 29 of IC403. When text is selected the text graphics are output as R.G.B signals on pins 15/16/17 of the micro and fed to pins 34/35/36 of IC403. At the same time pin 18 of the micro goes high taking pin 37 of IC403 high, blanking the picture and selecting text R.G.B. input.
Note: mixed mode is available and fast text with 8-page memory.
Video Path
The detected video signal is output from pins 18 of IC403, to sound traps Z403/404. The video is taken from the other side via the appropriate filter to Pin 18 of IC403. (1.2 p to p) Video to the Scart connectors is taken after R458 to Pin 19 of the Scart connector. The CVBS_TXT output Pin29 output is fed to IC501 Pin 34 (for Teletext). The video signal is sometimes labelled CVBS on the circuit diagram. This stands for Composite Video Blanking & Sync.
The composite signal is input Pin 13 (Video input) of IC403. This IC carries out all of the luma/Chroma processing internally and also provides the customer control functions of brightness, contrast, sharpness and saturation. IC403 is I²C bus controlled and incorporates auto grayscale circuitry and internal luma/chroma delay lines. The resulting R.G.B drive is output on pins 30,31 and 32. The R.G.B passes via connector PL405 to the CRT base PCB. Here the R.G.B signal is amplified by IC901 to provide drive for the cathodes of the CRT. IC901 produces a feedback signal, which is fed to IC403 (pin 33) for blanking and auto grayscale correction.
Sound Path
The demodulated mono sound is taken from pin 55 of IC403 directly to the sound output stage IC401 Pin 7. The output signal from IC401 is Volume controlled achieved within IC403 using the I²C bus line from IC501. To limit the volume at the specified out put the A_out pin 55 is fed to IC 401 through a voltage divider R455 and R454. Muting of the output stage is provided from Pin 46 of IC501 to pin3 of IC401/6 of IC301.
IN the stereo model the IF from PINS 10 & 11 of the tuner passes through Z401 and the output signal goes through pins 1&2 of IC403. The output QSS signal from IC 403 is taken from pin 11 and sent to audio processor IC700. The left channel is output on PIN 29 and the right channel output is on PIN 28. Then to IC301 after passing through a voltage divider R454/R455 for the right channel and R463/R464 for the left channel.
IC403 handles also the AM modulated signals in L/L’ systems at pins 1&2.
DIGITAL TV sound processor MSP34X0
The MSP 34x0G 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 34x0G. Only the MSP 3410 does digital demodulation and decoding of NICAM-coded TV stereo sound. The MSP 34x0G offers a powerful feature to calculate the carrier field strength which can be used for automatic standard detection (terrestrial) and search algorithms (satellite).
Sound output stage TDA7266L/TDA7266
TDA7266L is used as the AF output amplifier for mono applications. It is supplied by +12 VDC coming from a separate winding in the SMPS transformer. An output power of 4 W (THD = 0.5 %) can be delivered into an 16 ohm load.
TDA7266 is used as the AF output amplifier for stereo applications. It is supplied by +12 VDC coming from a separate winding in the SMPS transformer. An output power of 2*4W (THD = 0.5 %) can be delivered into an 16 ohm load.
Vertical output stage - TDA8174A
The TDA8174A is a power amplifier circuit for use in 90° and 110° color deflection systems for 25 to 200 Hz field frequencies, and for 4 : 3 and 16 : 9 picture tubes.
IC403 generates a vertical pulse signal VER_OUT and V_AMP that are fed to IC600 (the vertical stage IC). IC600 is supplied by a 26V DC via diode D610. It generates its own ramp signal and based on the V_AMP & VER_OUT signals it produces the vertical deflection signals that are fed to connector PL601. Vertical linearity adjustment is controlled by Q604, which is driven by the PWM output of IC501 at pin 49. Vertical position adjustment is conducted by Q606 derived by the VER_OUT signal. Switching Q606 will change the DC voltage on VOUT_2 pin, which will either lower or higher the picture. A DC level is supplied at VOUT_2 via D614 to stabilize the picture and make its position changeable.
Power supply (SMPS)
The DC voltage 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 126 V (Flat models) or 116 V (non Flat models) for FBT input, +/- 14 V for audio output IC, S + 3.3, S + 5 V and 8 V for ST92195.
The ZX series of receivers incorporate a Motorola switch mode power supply using a MC 44608 regulator controller IC. The circuit provides power to the receiver in both standby and normal operation modes.
Start Up
The switch on the mains supply is fed through the mains filter network TR801, the surge limiter resistor R828, the bridge rectifier diodes D811/13/37/38, and reservoir capacitor producing approx. 320 volts D.C. to feed the switching MOSFET Q801 via the primary winding of TR802 pins 6 and 7.
Start up resistor R801 feeds from a 500V coming from the mains through the adder diodes D809, D890 to pin 8 of IC800, the IC uses 9mA current source and connects it internally to VCC at pin6 allowing a rapid charge enough for start up. Then IC800 responds with the oscillator starting to oscillate at a 40 KHz frequency fixed by the IC manufacturer.
The IC then produces, pulse width modulation pulses, at this frequency on pin 5 to drive the base of the switching FET Q801, that will then switch current on and off through the primary of TR802, which will in turn provides voltages in the secondary windings. The secondary winding voltages being proportional to the length of time that Q801 is turned on in each cycle. The voltage produced between pins 4 and 3 of TR802 is rectified by D804 developing aprox. 12 volts on C810, which takes over from the start up resistor to supply pin 8 of IC800.
The Demag pin at pin1 offers 3 different functions: Zero voltage crossing detection (50mV), 24mA current detection and 120mA current detection. The 24mA level is used to detect the secondary reconfiguration status and the 120mA level to detect an Over Voltage status called Quick OVP.
The VCC at pin6 operates between 6,6V and 13V in normal operation, when this voltage exceeds 15V then the IC output is disabled.
Voltage Regulation
After initial start up the secondary voltages of TR802 are established. These voltages then need to be regulated to the required levels. In a switch mode power supply such as this, it is the ON time of the switching FET Q801 that determines the output voltages produced. To provide regulation of the supply there is a feedback loop via an adjustable zener IC118 and an OPTO- coupler connected to pin3 of IC800. The reference voltage of IC118 is set to 2,5V to supply a B+ voltage of 115V. Any fluctuation at this pin will cause IC800 to compensate it either by increasing or decreasing the voltage at the secondary outputs.
Voltage Protection
The MC44608 offers two OVP functions:
1- A fixed function that detects when V CC is higher than 15.4V
2- A programmable function that uses the demag pin. The current flowing into the demag pin is mirrored and compared to the reference current Iovp (120mA). -Thus this OVP is quicker than normal number one as it directly senses the change in current rather than waiting for a specific voltage value, and is called QOVP. In both cases, once an OVP condition is detected, the output is latched off until a new circuit START–UP.
3- A software controlled function acts on pin52 of IC501. This pin monitors feedback from both 8V and 5V via D512, then compares these to a reference value Vref pre-set by the hardware through resistors R545, R546, R548. In normal mode operation 1.2V < Vref < 2.4V. Any voltage outside this window will cause the micro controller to force the TV to stand by mode by lowering the standby port. Refer to standby mode.
Current Protection
To monitor the current drawn by the receiver the source of Q801 is returned to the bridge rectifier through a low value resistor R807. All the current drawn by the receiver will flow through that resistor each time Q801 conducts; this will produce a voltage across the resistors proportional to the current drawn by the receiver. This voltage is fed to pin 2 of IC800 via R806. When the receiver is working normally the voltage across R807 is only a fraction of a volt and is not large enough to have any effect on IC800. Under fault conditions, if the receiver draws excessive current the voltage across R807 will rise. This voltage is monitored by the current sense input pin2.
This Current Sense pin senses the voltage developed on the series resistor R806 inserted in the source of the power MOSFET. When I sense reaches 1V, the Driver output (pin 5) is disabled. This is known as the Over Current Protection function. A 200mA current source is flowing out of the pin 3 during the start–up phase and during the switching phase in case of the Pulsed Mode of operation. A resistor can be inserted between the sense resistor and the pin 3, thus a programmable peak current detection can be performed during the SMPS stand–by mode.
Standby Operation
As mentioned earlier the Start–up Management of MC44608 is as follows:
The Vi pin 8 of IC800 is directly connected to the HV DC rail Vin. This high voltage current source is internally connected to the VCC pin and thus issued to charge the VCC capacitor. The V CC capacitor charge period corresponds to the Start–up phase. When the V CC voltage reaches 13V, the high voltage 9mA current source is disabled and the device starts working. The device enters into the switching phase.
To help increase the application safety against high voltage spike on pin8 a small wattage 1k _ series resistor is inserted between the Vin rail and pin 8. After this start-up the IC can distinguish between the different modes of operation using the following technique:
Mode Transition
The LW latch is the memory of the working status at the end of every switching sequence. Two different cases must be considered for the logic at the termination of the SWITCHING PHASE:
1. No Over Current was observed
2. An Over Current was observed
These two cases correspond to the two signals “NOC” in case of “No Over Current” and “OC” in case of Over Current.
The effective working status at the end of the ON time memorised in LW corresponds to Q=1 for no over current, and Q=0 for over current.
To enter the standby mode secondary side is reconfigured using D889 loop, this starts with the microprocessor ‘s pin 47 becomes high; as the standby port becomes high Q503 conducts and Q802 becomes off then D889 conducts and the high voltage output value becomes lower than the NORMAL mode regulated value. The shunt regulator IC118 is fully OFF. In the SMPS stand–by mode all the SMPS outputs are lowered except for the low voltage output that supply the wake–up circuit located at the isolated side of the power supply. In that mode the secondary regulation is performed by the Zener diode (D801) connected in parallel to the TL431. The secondary reconfiguration status can be detected on the SMPS primary side by measuring the voltage level at pin4 of TR802.
In the SMPS stand–by mode the 3 distinct phases are:
The SWITCHING PHASE: Similar to the Overload mode. The current sense clamping level is reduced. When VCC crosses the current sense section, the C.S. clamping level depends on the power to be delivered to the load during the SMPS stand–by mode. Every switching sequence ON/OFF is terminated by an OC as long as the secondary Zener
diode voltage has not been reached. When the Zener voltage is reached the ON cycle is terminated by a true PWM action. The proper SWITCHING PHASE termination must correspond to a NOC condition. The LW latch stores this NOC status. The LATCHED OFF PHASE: The MODE latch is set.
The START–UP PHASE is similar to the Overload Mode. The MODE latch remains in its set status (Q=1).
The SWITCHING PHASE: The Stand-by signal is validated and the 200uA is sourced out of the Current Sense pin 2.
SMPS Switch Off
When the mains is switched OFF, so long as the electrolytic bulk capacitor provides energy to the SMPS the controller remains in the switching phase. Then the peak current reaches its maximum peak value, the switching frequency decreases and all the secondary voltages are reduced. The V CC voltage is also reduced. When VCC is less than 6,5V, the SMPS stops working
Line circuit
Line and frame drive are generated by IC403. The sync pulses are separated from the incoming video signal at pin 18/ 20/22 and used to control the internal circuitry of the IC. Line drive is produced by counting down the external 4.43 MHz crystal at pin 40 to 15.625 KHz locked to the incoming sync. This drive is output on pin 48 and feeds directly to the line drive transistor Q601. Note. That the output of IC403 Pin 48 is an open-collector and requires a pull up resistor, if the pin is open circuited for test no waveform will be seen. Q601 collector feeds the line output transistor Q603.
The line output stage is conventional with a transformer containing a split diode winding for EHT generation. Fifth harmonic tuning is achieved by capacitor C618/619.
A fly-back pulse is taken from pin 1 of the FBT transformer. This is required by IC403 (Pin 49) for burst / sync gating, and RGB line blanking. The ver_sync signal is output from the pin47 and fed to Pin41 of IC501. The H_sync pulse is taken from pin 1 of the FBT and fed to the micro at pin 40. These two signals are required by the micro for graphics timing and also for text.
B.C.L Circuit (Beam Current Limiter)
Beam current limiting is employed to protect the circuitry in the receiver, the CRT and to prevent excessive X Ray radiation in fault conditions. The current drawn by the CRT is monitored by the current drawn through the winding of the fly-back transformer that produces the EHT for the CRT anode. The end of the winding (Pin 10) is returned to IC403
Pins 46, the beam current drawn by the CRT passes through Q603 and develops a voltage on the collector proportional to the current (V=IxR).
The voltage on the collector will vary depending on the beam current being drawn reducing the brightness and contrast of the picture. If the voltage is sufficiently negative (indicating very high excess beam current) the output will be reduced, reducing the picture brightness and contrast.
Serial access CMOS 8K EEPROM 24C08
The 24C08 is a 8 Kbit 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.
EEPROM Initialization
If the E²PROM IC500 is replaced it will come fully programmed and therefore it is not necessary to initialize the new device. In some circumstances the E²PROM may become corrupted in use i.e. static discharge or lightning strike. If this happens, it is advised that the E²PROM is replaced.
MSP34X0G
The MSP 34x0G family of single-chip Multistandard Sound Processors covers the sound processing of all analog TVStandards 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 3 shows a simplified functional block diagram of the MSP 34x0G. This new generation of TV sound processing ICs now includes 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 standard.
Current ICs have to perform adjustment procedures in order to achieve good stereo separation for BTSC and EIA-J.
The MSP 34x0G has optimum stereo performance without any adjustments. All MSP 34xxG versions are pin compatible to the MSP 34xxD. Only minor modifications are necessary to adapt a MSP 34xxD controlling software to the MSP 34xxG. The MSP 34x0G further simplifies controlling software.
Standard selection requires a single I2C transmission only. The MSP 34x0G 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 Sound Selection). The MSP 34x0G can handle very high FM deviations even in conjunction with NICAM processing. This is especially important for the introduction of NICAM in China. The ICs are produced in submicron CMOS technology.
Service Menu (Service mode)
All system, geometry and white balance alignments are performed in Service Mode. Before starting the service mode alignments, make sure that all manual adjustments are done correctly.
To enter the service mode:
1. Press the MENU button on the remote control gun.
2. Press digit keys 4, 7, 2 and 5 consecutively.
1. Use the CURSOR UP  / DOWN  buttons to move between the registers.
2. Use the CURSOR LEFT / RIGHT buttons to change the data. See figure 5.
To memorize the adjustment:
It is not required to memorize the adjustment. Data are stored automatically.
To exit the Service Mode:
Switch the TV off using the mains switch.
Service Adjustments default values.
Using Colored Buttons
By using the four coloured buttons on the remote control different features or adjust may be accessed.
AVL
Press the RED button to activate or deactivate the AVL (Automatic Volume Level, between different broadcast channels).
GEOMETRY MENU
Press the GREEN button in order to change from the Main Service Menu to the Geometry Menu,
To return to the Main Service Menu it should be pressed the Menu button.
In the bottom area of this Menu, it can be seen “AUTO”. By pressing the WIDE MODE button it changes to 4:3 or 16:9 format. To perform the Geometry adjustments select the most suitable option:
- AUTO, entering 4:3 or 16:9 signal and proceeding with adjustments as below.
- 4:3, entering 4:3 signal and proceeding with adjustments as below.
- 16:9, entering 16:9 signal and proceeding with adjustments.