Vestel 11AK26-5 Schematic
CONTENTS
Contents ................................................................................................................................................................................... 1
Safety Precautions ................................................................................................................................................................... 2
TV Set switched off .................................................................................................................................................................. 2
Measurements .......................................................................................................................................................................... 2
PERI-TV SOCKET ................................................................................................................................................................... 2
SCART 1 ................................................................................................................................................................................... 2
INTRODUCTION ......................................................................................................................................................................... 2
SMALL SIGNAL PART WITH TDA884X .................................................................................................................................. 2-3
TUNER...................................................................................................................................................................................... 4
SOUND OUTPUT STAGE TDA2614 .......................................................................................................................................... 4
VERTICAL OUTPUT STAGE WITH TDATDA8356 ..................................................................................................................... 4
VIDEO OUTPUT AMPLIFIER TDA6107Q .................................................................................................................................... 4
POWER SUPPLY (SMPS) .......................................................................................................................................................... 4
MICROCONTROLLER SDA545X ............................................................................................................................................... 5
SERIAL ACCESS CMOS 8K (1024*8) EEPROM ST24C08 ........................................................................................................ 5
SAW FILTERS ........................................................................................................................................................................... 5
IC DESCRIPTIONS AND INTERNAL BLOCK DIAGRAM ............................................................................................................. 5
TDA8840/TDA8842 ............................................................................................................................................................ 5-6
UV1316/UV1336 ................................................................................................................................................................ 7
TDA2614 ............................................................................................................................................................................ 7-8
TDA8356 ............................................................................................................................................................................ 8
TDA6107Q .......................................................................................................................................................................... 8
MC44604 ............................................................................................................................................................................ 9
SDA545X ............................................................................................................................................................................ 9-11
ST24C08 ............................................................................................................................................................................. 11
G1965M .............................................................................................................................................................................. 11
AK26 CHASSIS MANUAL ADJUSTMENT PROCEDURE .......................................................................................................... 11
For Adjust Settings ............................................................................................................................................................. 11
WHITE BALANCE ADJUSTMENT ........................................................................................................................................ 11
AGC ADJUSTMENT ............................................................................................................................................................ 11
IF-PLL NEGATIVE ADJUSTMENT ........................................................................................................................................ 12
4 : 3 HORIZONTAL SHIFT ADJUSTMENT ....................................................................................................................... 12
4 : 3 VERTICAL SLOPE ADJUSTMENT ........................................................................................................................... 12
4 : 3 VERTICAL AMPLITUDE ADJUSTMENT ................................................................................................................... 12
4 : 3 S-CORRECTION ADJUSTMENT .............................................................................................................................. 12
4 : 3 VERTICAL SHIFT ADJUSTMENT ............................................................................................................................ 12
For Option Settings ................................................................................................................................................................... 12
OPTION 00 .......................................................................................................................................................................... 12-13
OPTION 01 .......................................................................................................................................................................... 13-14
OPTION 02 .......................................................................................................................................................................... 13
OPTION 03 .......................................................................................................................................................................... 14
OPTION 04 .......................................................................................................................................................................... 14
OPTION 05 .......................................................................................................................................................................... 14
OPTION 06 .......................................................................................................................................................................... 14
OPTION 07 .......................................................................................................................................................................... 15
GENERAL BLOCK DIAGRAM OF CHASSIS AK26 ................................................................................................................... 16
ELECTRONIC COMPONENT PART LIST .................................................................................................................................... 17-18
1
DO NOT CHANGE ANY MODULE UNLESS THE SET IS SWITCH OFF
The mains supply side of the switch mode power supply transformer is live.
Use an isolating transformer.
The receivers fulfill completely the safety requirements.
Safety precautions:
Servicing of this TV should only be carried out by a qualified person.
- 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 fusable 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 C804 (150mF) before changing IC802 or other components in primary side of SMPS.
Measurements:
Voltage readings and oscilloscope traces are measured under following conditions.
Antenna signal 60dB from colourbar generator. (100% white, 75% colour saturation)
Brightness, contrast, colour set for a normal picture.
Mains supply, 110VAC, 60Hz.
PERI-TV SOCKET
SCART 1 (SC050)
1 Audio right output 0.5Vrms / 1K
2 Audio right input 0.5Vrms / 10K
3 Audio left output 0.5Vrms / 1K
4 Ground AF
5 Ground Blue
6 Audio left input 0.5Vrms / 10K
7 Blue input 0.7Vpp / 75ohm
8 AV switching input 0-12VDC /10K
9 Ground Green
10 11 Green input 0.7Vpp / 75ohm
12 13 Ground Red
14 Ground Blanking
15 Red input 0.7Vpp / 75ohm
16 Blanking input 0-0.4VDC, 1-3VDC / 75ohm
17 Ground CVS output
18 Ground CVS input
19 CVS output 1Vpp / 75ohm
20 CVS input 1Vpp / 75ohm
21 Ground
1. INTRODUCTION
11AK26 is a 90ø chassis capable of driving 14 tubes at appropriate currents.
The chassis is capable of working in PAL M, PAL N, PAL B/G and NTSC M. The sound system is capable of giving 2.5 watts
RMS output into a load of 16 ohms.
2. SMALL SIGNAL PART WITH TDA884X
The TDA8840/8842/8844 combine all small signal functions required for a colour TV receiver, except tuning.
2.1. Vision IF amplifier
The IF-amplifier contains 3 AC-coupled control stages with a total gain control range which is higher than 66dB.
The sensitivity of the circuit is comparable with that of modern IF-IC s. The video signal is demodulated by means of a PLL
carrier regenerator. This circuit contains a frequency detector and a phase detector. The AFC output is obtained by using the
VCO control voltage of the PLL and can be read via the I²C-bus. For fast search tuning systems the window of
the AFC can be increased with a factor 3. The setting is realised with the AFW bit.
Depending on the type the AGC-detector operates on top-sync level (single standard versions) or on top sync and top
white-level (multi standard versions). The demodulation polarity is switched via the I²C-bus. The AGC detector time-constant capacitor
is connected externally. This mainly because of the flexibility of the application. The time-constant of the AGC system during positive
2
modulation is rather long to avoid visible variations of the signal amplitude. To improve the speed of the AGC system a circuit has
been included which detects whether the AGC detector is activated every frame period. When during 3 frame periods no action is
detected the speed of the system is increased. For signals without peak white information the system switches automatically to a
gated black level AGC. Because a black level clamp pulse is required for this way of operation the circuit will only switch to black level
AGC in the internal mode.
The circuits contain a video identification circuit which is independent of the synchronisation circuit. Therefore search tuning is
possible when the display section of the receiver is used as a monitor. The ident output is supplied to the tuning system via
the I²C-bus. The video ident circuit can be made less sensitive by means of the STM bit. This mode can be used during search
tuning
to avoid that the tuning system will stop at very weak input signals.
2.2. Video Switches
The circuits have two CVBS inputs (internal and external CVBS) and Y/C input. When the Y/C input is not required the Y input can be
used as third CVBS input. The selection of the various sources is made via the I²C-bus. The circuit has one CVBS output.
2.3. Sound Circuit
The sound band pass and trap filters have to be connected externally. The filtered intercarrier signal is fed to a limiter circuit
and is demodulated by means of a PLL demodulator. This PLL circuit tunes itself automatically to the incoming carrier signal
so that no adjustment is required.
The volume is controlled via the I²C-bus. The deemphasis capacitor has to be connected externally. The non-controlled audio
signal can be obtained from this pin. The FM demodulator can be muted via the I²C-bus. This function can be used to switch-off
the sound during a channel change so that high output peaks are prevented. The TDA8840/8842 contain an automatic volume
levelling (AVL) circuit which automatically stabilises the audio output signal to a certain level which can be set by the viewer by means
of the volume control. This function prevents big audio output fluctuations due to variations of the modulation depth of the transmitter.
The AVL function can be activated via the I²C-bus.
2.4. Synchronisation circuit
The sync seperator is preceded by a controlled amplifier which adjusts the sync pulse amplitude to a fixed level. These pulses are fed
to the slicing stage which is operating at 50% of the amplitude. The separated sync pulses are fed to the first phase detector and to the
coincidence detector. This coincidence detector is used to detect whether the line oscillator is synchronised and can also be used for
transmitter identification. The first PLL has a very high statical steepness so that the phase of the picture is independent of the line
frequency.
The horizontal output signal is generated by means of an oscillator which is running at twice the line frequency. Its frequency is divided
by 2 to lock the first control loop to the incoming signal. The time-constant of the loop can be forced by the I²C-bus (fast or slow).
If required the IC can select the time-constant depending on the noise content of the incoming video signal.
To protect the horizontal output transistor, the horizontal drive is immediately switched off when a power-on-reset is detected.
The drive signal is switched-on again when the normal switch-on procedure is followed.
Via the I²C-bus, adjustments can be made of the horizontal and vertical geometry. The vertical sawtooth generator drives the
vertical output drive circuit which has a differrential output current. For the EW drive a single ended current output is available.
When the horizontal scan is reduced to display 4 : 3 pictures on a 16 : 9 picture tube an accurate video blanking can be switched on
to obtain well defined edges on the screen.
Overvoltage conditions can be detected via the EHT tracking pin.When an overvoltage condition is detected the horizontal output
drive signal will be switched-off via the slow stop procedure but it is also possible that the drive is not switched-off and that just a
protection indication is given in the I²C-bus output byte. The choice is made via the input bit PRD.
2.5. Chroma and Luminance processing
The circuits contain a chroma bandpass and trap circuit. The filters are realised by means of gyrator circuits and they are
automatically calibrated by comparing the tuning frequency with the X-tal frequency of the decoder.
The luminance delay line and the delay for the peaking circuit are also realised by means of gyrator circuits.
The centre frequency of the chroma bandpass filter is switchable via the I²C-bus so that the performance can be optimised for
front-end signals and external CVBS signals.
During SECAM reception the centre frequency of the chroma trap is reduced to get a better suppression of the SECAM
carrier frequencies.
2.6. Colour Decoder
The decoder contains an alignment-free X-tal oscillator, a killer circuit and two colour difference demodulators. The 90° phase shift for
the reference signal is made internally.
The IC contains an automatic colour limiting (ACL) circuit which 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 base-band delay line is integrated in the PAL/SECAM IC s.
The demodulated colour difference signals are internally supplied to the delay line. The matrixed signals are externally available.
The colour difference matrix switches automatically between
PAL/SECAM and NTSC, however, it is also possible to fix the matrix in the PAL standard.
Which colour standard the IC can decode depends on the external X-tals. The X-tal to be connected to pin 34 must have a frequency
of 3.5 MHz (NTSC-M, PAL-M or PAL-N) and pin 35 can handle X-tals with a frequency of 4.4 and 3.5 MHz. To prevent calibration
problems of the horizontal oscillator the external switching between the 2 X-tals should be carried out when the oscillator is forced to
pin 35. For a reliable calibration of the horizontal oscillator it is very important that the X-tal indication bits (XA and XB) are not
corrupted. For this reason the X-tal bits can be read in the output bytes so that the software can check the I²C-bus transmission.
2.7. RGB output circuit and black-current stabilisation
The colour-difference signals are matrixed with the luminance signal to obtain the RGB-signals. The TDA 884X device has one linear
RGB input. This RGB signal can be controlled on contrast and brightness.
The output signal has an amplitude of about 2 volts black-to-white at nominal input signals and nominal settings of the controls.
To increase the flexibility of the IC it is possible to insert OSD and/or teletext signals directly at the RGB outputs.
This insertion mode is controlled via the insertion input (pin 26 in the S-DIP 56- and pin 38 in the QFP-64 level). This blanking action
at the RGB outputs has some delay which must be compansated externally.
To obtain an accurate biasing of the picture tube a Continuous Cathode Calibration circuit has been developed.
This function is realised by means of a 2-point black level stabilisation circuit.
When the TV receiver is switched-on, the RGB output signals are blanked and the black current loop will try to set the right picture
tube bias levels.Via the AST bit a choice can be made between automatic start-up or a start-up via the m-processor.
3
3. TUNER
Either a PLL or a VST tuner is used as a tuner.
UV1336 (VHF/UHF) is used as a PLL tuner. For only PAL B/G applications UV 1316 is used as the PLL tuner.
Channel coverage of UV1316:
BAND
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.
OFF-AIR CHANNELS CABLE CHANNELS
CHANNELS FREQUENCY CHANNELS FREQUENCY
RANGE (MHz) RANGE (MHz)
Noise Typical Max. Gain Min. Typical Max.
Low band : 5dB 9dB All channels : 38dB 44dB 52dB
Mid band : 5dB 9dB Gain Taper (of-air channels) : - - 8dB
High band : 6dB 9dB
Channel Coverage UV1336:
BAND CHANNELS FREQUENCY
RANGE (MHz)
Low Band 2 to D 55.25 to 139.25
Mid Band E to PP 145.25 to 391.25
High Band QQ to 69 397.25 to 801.25
Noise is typically 6dB for all channels. Gain is minimum 38dB and maximum 50dB for all channels.
4. SOUND OUTPUT STAGE TDA2614
TDA2614 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 2.5W (THD=0.5%) can be delivered into an 16 ohm load.
5. VERTICAL OUTPUT STAGE WITH TDA 8356
The TDA 8356 vertical deflection circuit is used in 90° deflection systems with field frequencies from
50 up to 120Hz. With its bridge configuration the deflection output can be DC coupled with few external components.
Only a single supply voltage for the scan and a second supply for the flyback are needed.
The drive voltage is amplified by an amplifier and fed to two amplifiers, one is inverting and the other is a non inverting amplifier.
The outputs (pins 7 and 4) are connected to the series connection of the vertical deflection coil and feedback resistor Rsense
(R702//R703). The voltage across Rsense is fed via pin 9 to correction amplifier, to obtain a deflection current which is proportional
to the drive voltage. The supply voltage for the TDA 8356 is 15VDC at pin 3. The supply voltage generator has a separate
supply voltage of 45VDC at pin 6.
6. VIDEO OUTPUT AMPLIFIER TDA6107Q
The TDA6107Q 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 sparkgap.
The TDA6107Q has an internal thermal protection circuit which gives a decrease of the slew rate at high temperatures.
Furthermore, the device needs only one power supply voltage (Vdd).
In contrast to previous types of DMOS video amplifiers, all the external resistors (Rf, Ri and Ra) are integrated, so the gain is fixed
and saves 9 resistors.
Furthermore, the reference voltage is integrated, it saves a resistor divider and a decoupling capacitor. So, the replacement
value of the TDA6107Q is very high.
The TDA6107Q is provided with a black current data pin. Since TDA884X is used as drive device, no adjustments are required
for gain and black setting, as the TDA884X has I²C white point adjustment and black current set-up.
7. POWER SUPPLY (SMPS)
The DC voltages required at various parts of the chassis are provided by an SMPS transformer controlled by the IC MC44604
which is designed for driving, controlling and protecting switching transistor of SMPS. The transformer produces 150/115V for
FBT input, ±14V for audio output IC, S+5V for microcontroller, +15V for vertical output (field scan) and +33V for tuner and some
other ICs and transistors.
4
8. MICROCONTROLLER SDA545X
The device is a control system based on the SDA 545X TV microcontroller. It is designed for a low
cost mono TV-SET with analogue picture and sound control. Neverthless the system offers an on screen display (OSD) and
IR remote control of all functions.
SDA545X has the following features:
- Display of program number, channel number, TV standard, analogue values, sleep timer, parental control, and mute is done by OSD.
- Single LED for IR active, standby and on mode indication.
- 1 Control line to select external source.
- 3 Control lines for TV standard selection.
- Frequency synthesis tuning (62.5 kHz steps)
- 192 step fine tuning
- Channels corresponding to standards PAL M/N NTSC M
- Mono sound control by analogue voltage
- System configuration with service mode
9. SERIAL ACCESS CMOS 8K (1024*8) EEPROM ST24C08
The ST24C08 is a 8Kbit electrically erasable programmable memory (EEPROM), organised as 4 blocks of 256*8 bits.
The memory is compatible with the I²C standard, two wire serial interface which uses a bi-directional data bus and serial clock.
The memory carries a built-in 4 bit, unique device identification code (1010) corresponding to the I²C bus definition.
This is used together with 1 chip enable input (E) so that up to 2*8K devices may be attached to the I²C bus and selected individually.
10. SAW FILTERS
Saw filter type : Model:
G1965M : PAL-SECAM B/G MONO
K2955M : PAL-SECAM B/G-D/K MONO, PAL-SECAM B/G-D/K-I, MONO, PAL-SECAM B/G-D/K-L MONO
K2958M : PAL-SECAM B/G-D/K (38) MONO
K2962M : PAL-SECAM B/G-L/L MONO
K6259K : PAL-SECAM B/G-D/K-I-M/N (EURO) MONO
M1963M : PAL M/N MONO, NTSC M MONO, PAL M/N-NTSC M MONO
IC DESCRIPTIONS AND INTERNAL BLOCK DIAGRAM
n TDA8840/8842/8844
n TUNER (UV1316, UV1336)
n TDA2614
n TDA8356
n TDA6107Q
n MC44604
n SDA545X
n ST24C08
TDA8840/8842:
The TDA884X is I^2C-bus controlled single chip TV processor which is intended to be applied in PAL, NTSC, PAL/NTSC and
multi-standard television receivers. These IC s are nearly pin compatible with the TDA837X TV processors but have a higher
degree of integration because the delay line (TDA4665 function) and the SECAM decoder have been integrated. In addition to
these functions some additional features have been added like Continuous Cathode Calibration (2-point black current loop
which results in an accurate biasing of the 3 guns), adjustable luminance delay time, blue stretching and dynamic skin tone control.
Features:
n Vision IF circuit with PLL demodulator
n Alignment-free multi-standard FM sound demodulator (4.5 MHz to 6.5 MHz)
n Audio switch
n Flexible source selection with CVBS switch and Y(CVBS)/C input so that a comb filter can be applied
n Integrated chrominance trap circuit
n Integrated luminance delay line
n Asymmetrical peaking in the luminance channel with a noise coring function
n Black stretching of non-standard CVBS or luminance signals
n Integrated chroma band-pass filter with switchable center frequency
n Blue stretch circuit which offsets colours near white towards blue
n RGB control circuit with Continuous Cathode Calibration and white point adjustment
n Linear RGB inputs and fast blanking
n Possibility to insert a blue black option when no video signal is available
n Horizontal synchronisation with two control loops and alignment-free horizontal oscillator
n Vertical count-down circuit
n Vertical driver optimised for DC-coupled vertical output stages
n I^2C-bus control of various functions
n Low dissipation (850 mW)
Functional Differences between 8840 and 8842
5
IC VERSION (TDA) 8840 8842
Multi-standard IF X
Automatic Volume Limiting X X
PAL Decoder X X
SECAM Decoder X
NTSC Decoder X
Dynamic Skin Control
Colour Matrix PAL/NTSC (Japan) X
Colour Matrix NTSC Japan/USA
YUV interface
Base-band delay line X X
Vertical zoom X X
PINNING PIN VALUE
1. Sound IF input : 1mVrms
2. External audio input : 500mVrms
3. IF demodulator tuned circuit 1
4. IF demodulator tuned circuit 2
5. IF-PLL loop filter : Min:32-Max:60 MHz
6. IF video output : 4.7V (Negative Modulation), 2V (Positive Modulation)
7. Serial clock input : Low level max:1.5 V, High level min 3.5V
8. Serial data input/output : Low level max:1.5 V, High level min 3.5V
9. Bandgap decoupling
10. Chrominance input (S-VHS) : 1Vpp, Max:1.4Vpp
11. External CVBS/Y input : 1Vpp, Max:1.4Vpp
12. Main supply voltage 1 : 8V, Min:7.2V, Max:8.8V
13. Internal CVBS input : 1Vpp, Max:1.4Vpp
14. Ground 1
15. Audio output : 700mVrms, Min:500mVrms, Max:900mVrms
16. SECAM PLL decoupling
17. External CVBS input : Vpp, Max:1.4Vpp
18. Black-current input : Amplitude of low reference current : 8mA
Amplitude of high reference current : 20mA
19. Blue output : 2Vpp
20. Green output : 2Vpp
21. Red output : 2Vpp
22. Beam current limiter input/V-guard input
23. Red input for insertion : 0.7Vpp, Max:0.8Vpp
24. Green input for insertion : 0.7Vpp, Max:0.8Vpp
25. Blue input for insertion : 0.7Vpp, Max:0.8Vpp
26. RGB insertion input : Max:0.3V
27. Luminance input : 1.4Vpp
28. Luminance output : 1.4Vpp
29. (B-Y) signal output : 1.05Vpp
30. (R-Y) signal output : 1.05Vpp
31. (B-Y) signal input : 1.05Vpp
32. (R-Y) signal input : 1.05Vpp
33. Subcarrier reference output : 3.58/4.43 MHz
34. 3.58 MHz crystal connection
35. 4.43/3.58 MHz crystal connection
36. Loop filter phase detector
37. 2nd
supply voltage 1 : 8V, Min:7.2V, Max:8.8V
38. CVBS output : 1Vpp, Max:1.4Vpp
39. Decoupling digital supply : 1.8V
40. Horizontal output : Max: 0.3V
41. Flyback input/sandcastle output : Min:100ma, Max:300mA
42. Phase-2 filter : 150 ms/ms
43. Phase-1 filter : ±0.9 kHz, Max: ±1.2 kHz
44. Ground 2
45. East-west drive output
46. Vertical drive A output : 0.95mA
47. Vertical drive B output : 0.95mA
48. IF input 1
49. IF input 2
50. EHT/overvoltage protection input : Min:1.2V, Max : 2.8V
51. Vertical sawtooth capacitor : 3Vpp
52. Reference current input : 3Vpp
53. AGC decoupling capacitor
54. Tuner AGC output : Max:9V (Maximum tuner AGC output voltage), 300mV (Output saturation voltage)
55.Audio deemphasis : 500mVrms
56. Decoupling sound demodulator
6
Loading...