11AK19_full.pdf

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, 220VAC, 50Hz.

PERI-TV SOCKET

SCART 1 (SC050)

SCART 2 (SC051)

Audio right output

0.5Vrms / 1K

Audio right output

0.5Vrms / 1K

Audio right input

0.5Vrms / 10K

Audio right input

0.5Vrms / 10K

Audio left output

0.5Vrms / 1K

Audio left output

0.5Vrms / 1K

Ground AF

Ground Blue

Audio left input

0.5Vrms / 10K

Audio left input

0.5Vrms / 10K

Blue input

0.7Vpp / 75ohm

Blue input

0.7Vpp / 75ohm

AV switching input

0-12VDC /10K

AV switching input

0-12VDC /10K

Ground Green

10 -

Green input

0.7Vpp / 75ohm

12 -

Ground Red

13 Ground Red

Ground Blanking

14 Ground Blanking

Red input

0.7Vpp / 75ohm

15 -

Blanking input

0-0.4VDC, 1-3VDC / 75ohm

16 -

Ground CVS output

17 Ground CVS output

Ground CVS input

18 Ground CVS input

CVS output

1Vpp / 75ohm

19 CVS output

1Vpp / 75ohm

CVS input

1Vpp / 75ohm

20 CVS input

1Vpp / 75ohm

Ground

21 Ground

* * ALL WIRES TO FRONT PANEL & LOUD SPEAKERS MUST BE ZIP-TIED TOGETHER AFTER ANY KIND OF REPAIREMENT

1. INTRODUCTION

11AK19 is a 90ø and 110ø chassis capable of driving 20-21,24,25,28-29,32,33 tubes at appropriate currents.

The chassis is capable of working in both PAL and SECAM. The sound system is capable of giving 6watts

RMS output into a load of 8ohms.

One 8 page simple TELETEXT, TOPTEXT and FASTEXT is provided.

The chassis is equipped with 21-pin scart connectors which can accept via scart the SVHS format from VCRs so equipped.

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

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. 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 CHANNELS CABLE CHANNELS

BAND

CHANNELS

FREQUENCY

CHANNELS

FREQUENCY

RANGE (MHz)

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.

Noise

Gain

Typical

Max.

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.

Channel Coverage of UV1315:

OFF-AIR CHANNELS

CABLE CHANNELS

BAND

CHANNELS

FREQUENCY

CHANNELS

FREQUENCY

RANGE (MHz)

Low Band

E2 to C

48.25 to 82.25 (1)

S01 to S10

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.

Noise

Typ.

Max.

Gain

Min.

Typ.

Max.

Low band

: 6dB

9dB

All Channels

38dB

44dB

50dB

Mid band

: 6dB

10dB

Gain Taper

8dB

High band

: 6dB

11dB

(off-air channels)

4.VIDEO SWITCH TEA6415C

In case of three or more external sources are used, the video switch IC TEA6415C is used. The main function of this device is to switch

8 video input sources on the 6 outputs.

Each output can be switched on only one of each input. On each input an alignment of the lowest level of the signal is made (bottom

of sync. top for CVBS or black level for RGB signals).

Each nominal gain between any input and output is 6.5dB.For D2MAC or Chroma signal the alignment is switched off by forcing, with

an external resistor bridge, 5VDC on the input. Each input can be used as a normal input or as a MAC or Chroma input (with external

resistor bridge). All the switching possibilities are changed through the BUS.

Driving 75ohm load needs an external resistor.

It is possible to have the same input connected to several outputs.

5. AM DEMODULATOR TDA9830

The TDA9830 is designed for AM-sound demodulation used in L and L standard.

Sound IF Input:

The sound IF amplifier consists of three AC-coupled differential amplifier stages each with approximately 20dB gain.

At the output of each stage is a multiplier for gain controlling. The overall control range is approximately -6 to +60dB and the

frequency response (-3dB) of the IF amplifier is approximately 6 to 70MHz. The steepness of gain control is approximately 10mV/dB.

IF AGC:

The automatic gain control voltage to maintain the AM demodulator output signal at a constant level is generated by a mean

level detector.The AGC-detector charges and discharges the capacitor at pin 3 controlled by the output signal of the

AM-demodulator compared to an internal reference voltage.The maximum charge/discharge current is approximately 5 mA.

AM-demodulator

The IF amplifier output signal is fed to a limiting amplifier (two stages) and to a multiplier circuit.

However the limiter output signal (which is not any more AM modulated) is also fed to the multiplier, which provides AM

demodulation (in phase demodulation). After lowpass filtering (fg @ 400kHz) for carrier rejection and buffering,

the demodulator output signal is present at pin 6.

Audio Switch

This circuit is an operational amplifier with three input stages and internal feedback network determining gain (0dB) and

frequency response (fg @ 700kHz). Two of the input stages are connected to pin 7 and pin 9, the third input stage to an

internal reference voltage. Controlled by the switching pins 10 and 12, one of the three input stages can be activated and a

choice made between two different AF signals or mute state. The selected signal is present at pin 8. The decoupling capacitors

at the input pins are needed, because the internally generated bias voltage for the input stages must not be influenced

by the application in order to avoid DC-plop in case of switching.

Reference Circuit:

This circuit is a band gap stabiliser in combination with a voltage regulation amplifier, which provides an internal reference voltage

of about 3.6V nearly independent from supply voltage and temperature. This reference voltage is filtered by the capacitor at

pin 4 in order to reduce noise. It is used as a reference to generate all important voltages and currents of the circuit.

For application in 12V power supply concepts, there is an internal voltage divider in combination with a Darlington transistor in

order to reduce the supply voltage for all IC function blocks to approximately 6V.

6. DIGITAL TV SOUND PROCESSOR TDA9875

The TDA9875 is a single-chip Digital TV Sound Processor.

Supported standards are M, B/G, D/K, I and L.

Description of the demodulator and decoder section:

SIF Input:

Two input pins are provided, SIF1 e.g. for terrestrial TV and SIF2 e.g. for a satellite tuner. The selected signal is passed through an

AGC circuit and then digitized by an 8-bit ADC operating at 24.576MHz.

AGC:

The gain of the AGC amplifier is controlled from the ADC output by means of a digital control loop employing hysteresis.

The AGC has a fast attack behaviour to prevent ADC overloads and slow decay behaviour AGC oscillations.

For AM demodulation AGC must be switched off.

Mixer

The digitized input signal is fed to the mixers, which mix one or both input sound carriers down to zero IF. A 24-bit control word for

each carrier sets the required frequency.

FM and AM Demodulation

An FM or AM input signal is fed via a band-limiting filter to a demodulator that can be used for either FM or AM demodulation.

Apart from the standard (fixed) de-emphasis characteristic, an adaptive de-emphasis is available for encoded satellite programs.

A stereo decoder recovers the left and right signal channels from the demodulated sound carriers.

FM Identification:

The identification of the FM sound mode is performed by AM synchronous demodulation of the pilot signal and narrow-band detection

of the identification frequencies. The result is available via the I²C-bus interface.

NICAM Demodulation:

The NICAM signal is transmitted in a DQPSK code at a bit rate of 728 kbit/s. The NICAM demodulator performs DQPSK

demodulation and feeds the resulting bitstream and clock signal onto the NICAM decoder and, for evaluation purposes, to PCLK

(pin 1) and NICAM (pin 2).

NICAM Decoder:

The device performs all decoding functions in accordance with the EBU NICAM 728 specification. After locking to the frame

alignment word, the data is descrambled by applying the defined pseudo-random binary sequence; the device will then synchronise

to the periodic frame flag bit C0.

The status of the NICAM decoder can be read out from the NICAM status register by the user. The OSB bit indicates that the

decoder has locked to the NICAM data. The VDSP bit indicates that the decoder has locked to the NICAM data and that the

data is valid sound data.

7. SOUND OUTPUT STAGE TDA2614/TDA2615/TDA2616Q

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*6W (THD=0.5%) can be delivered into an 8ohm load.

TDA2615 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*6W (THD=0.5%)

can be delivered into an 8ohm load.

TDA2616Q is used as the AF output amplifier for stereo and dolby prologic applications. It is supplied by ±16VDC coming from

a separate winding in the SMPS transformer. An output power of 2*12W (THD=0.5%) can be delivered into an 8ohm load.

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