For the main carrier two service positions are possible (3.1).
A: For faultfinding on the component side of the main carrier.
B: For (de) soldering activities on the copper side of the main carrier.
Position A can be reached by first removing the mains cord from it's fixation, then loosen the carrier lips (1) and then pulling the
carrier panel (2) for approximately 10cm.
Position B can be reached from position A after disconnecting the degaussing cable. Put the carrier on the line transformer side.
Fig. 3.1
Fig. 3.2
2
Overview oscillograms / Testpoints
3
Description of microprocessor and TXT in CTN chassis
MICROPROCESSOR + TXT
The CTN model chassis is designed to accept three different microcontrollers: the TMP47C634, the SAA5288 and the SAA5290.
The three microcontrollers are mounted in the same position, by placing pin 1 at the same point. The TMP47C634 has 42 pins while the SAA52XX
models have 52 pins. The circuitry connected to the pins is practically the same. From pin 21 on the Toshiba model, the equivalent pin on the
SAA52XX unit will be 10 numbers higher (e.g., pin 33 on the TMP47C634 corresponds to pin 43 on the SAA52XX).
The difference between the TMP47C634 and the SAA52XX is an improvement in the OSD (it goes from two lines to a full screen, thus making it
possible to implement the MENU) and the addition of new functions in the software (24-h timer, child block, etc.). The SAA5290 also has a TXT
decoder.
Following is an explanation of the different functions of the microcontrollers with indications as to the pin number assigned to each integrated circuit
and the differences between the microprocessors, where applicable:
- Integrated circuit power supply: The TMP47C634 has a single +5V power supply (pin 42 VVD). The SAA52XX has several power supplies for the
microcontroller (pin 44 VDDM), the analog converter and the OSD (VDDA pin 38 and VDDT pin 39), as well as for the final phase of RGB outputs
(RGBREF pin 31).
- LED (pin 20): The LED lights up with a low current when the television set is ON and with a high current when the set is on Standby.
- RC5 (pin 35 on the TMP47C634; pin 45 on the SAA52XX): The commands transmitted by the remote control handset are received by infrared
receiver 1685 and passed to the microcontroller for decoding.
- Switching voltages of the BG/L-L/L’-BG/I systems (pins 36, 37 and 38 on the TMP47C634; pins 46, 47 and 48 on the SAA52XX). Th ese signals are
only used on Multistandard units. These pins are used for switching the system f or decoding sound and video. These signals are inv erted and set at
the correct level by transistors 7672 and 7673, respectiv ely. Once they are transf ormed, together with the signal from pin 48 (BG/I), they make up the
system status lines (See table).
- Oscillator: The TMP47C634 has a 4-MHz oscillator which is determined by a 4-MHz ceramic resonator on pins 31 and 32. The SAA52XX has a 12MHz oscillator which is determined by a 12-MHz crystal between pins 41 and 42.
- On-Screen Display (OSD): In order to synchronize the OSD information with the picture signal, the VERT FLYBACK signal is added in inverted
form to the integrated circuit (pins 15 and 27 on the TMP47C634 and pin 37 on the SAA52XX), as is the HOR FLYBACK signal (pin 26 on the
TMP47C634 and pin 36 on the SAA52XX). The SAA5290 also uses these signals to synchronize the TXT. On the TMP47C634 there is an LC
network on pins 28 and 29 which controls the OSD.
The TMP47C634 has only the green output activated (pin 23) and this is inverted with transistor 7658 so that the correct level is reached. The
SAA52XX models have three outputs, R, G and B (pins 32, 33 and 34) with emitter followers (7641, 7642 and 7644).
The pin for erasing the RGB picture signal for inserting OSD (pin 25 on the Toshiba and 35 on the SAA52XX) is connected with diode 6679 to pin
21 on the TDA836X.
- Tuning: The unit has a VST (Voltage Synthesized tuning) system. This system wor ks by tuning to a station on the tuner through a linear variation
of the tuning voltage (0V2 to 5V). It is a vailable on pin 1 of the mC and converted to an adequate lev el on the selector/dial (0V to 33V), using T7605
and +101.5V. The AFC signal (Automatic Frequency Control) of detector FI is added to the tuning voltage V-VARI by R3689 and R3688 to compensate for the slow variation of the tuning feature.
While searching for the station, pin 41 is set on high which means that the AFC voltage will not be added to the V-VARI. If an IDENT signal is
received on pin 16 while searching for a station, the mC will check via entry pin 9 whether the tuning is correct and whether the AFC signal can be
activated again. The SAA52XX has 3 pins (15 VHF1, 17 VHFIII AND 18 UHF) for band switching and provides v oltage to the corresponding pin. The
TMP47C634 has only two pins (17, 18) for band switching which decode the 3 tuning lines using transistors 7003 and 7004.
The SAA52XX models also have pin 30, which they use to limit the CAS voltage in automatic tuning so that noise signals are not memorized.
- Picture and sound adjustments: volume control (pin 2), brightness control (pin 3), colour control (pin 4) and contrast control (pin 5); the SAA52XX
models also have sharpness control (pin 6).
4
The RC networks are used to convert the modulated pulse output to a DC voltage level. Some of these settings can be preprogrammed in the
memory for all channels as a personal preference (PP). Mute is controlled internally on the mC during automatic station search or when the signal
received is interrupted (detected via the IDENT signal on pin 16).
- Service: If pin 7 is connected to earth when the set is tur ned on from the IR, the unit will go into Service Default Mode (see Chapter 8).
- INT/EXT and mute on programme 0. The microcontrollers hav e a pin for s witching to external (pin 7 on the TMP47C634 and pin 8 on the SAA5290)
via transistors 7876 and 7877. This signal is added to the signal from SCART pin 8 so that either of them can be used to switch to external.
On units without SCART, this signal is used for muting the sound and picture on programme 0.
On the SAA52XX models, this line is also an input line so that the microcontroller knows if the unit is on external. This way, the correct video signal
is switched on the TXT and the sound is not muted on external, even if there is no pilot signal.
- EEPROM bus 12C memory (pins 39 and 40 on the TMP47C634; pins 49 and 50 on the SAA52XX); The microcontroller is connected to non-volatile
memory IC7685 (EEPROM) via bus 12C. Personal preferences (PP) and channel data are stored in the memory. The system can memorize 79
channels (with the data on tuning voltage, band and system) and the personal preferences.
- Standby (pin 19); The Standby switching signal is on pin 19 of the mC . If the Standby signal is “low”, it reduces the start-up voltage of oscillator pin
36 on the TDA836X, thus cutting the line voltages.
- Control and options keypad; The decoding principle is different depending on the unit. On the TMP47C634, it decodes a matrix between pins 11,
12 and 13 while on the SAA52XX, it only checks to see if the pin is earthed. The TMP47C634 also checks for diodes 6603, 6604 and 6605 via pin
14 on the microcontroller (see options table on diagram).
The SAA52XX reads the options via pins 14 and 52, which will be “1” or “0” depending on the components (2690, 3600, 3650 and 3657).
- TXT: The SAA5290 has an internal teletext decoder. The following functions have been programmed on the software: TXT input/output, show,
freeze, temporary cancellation, clock, subcode, zoom, inde x, flof, page +/-, X/26 and 8/30 pac k et decoding (station identification and start-up page).
Synchronization is received from the HOR FLY and VERT FLY signals, as is the OSD (this means that if the video signal is lost, the TXT does not
become unsynchronized). The teletext information is extracted from the video signal inserted on pins 23 (internal video) and 24 (external video) via
condensers 2635 and 2636.
Pin 27 corresponds to the NIL control signal, which pulse switches transistor 7640 and keeps the picture from interlacing when applied to the
vertical deflector.
All remaining circuitry (oscillator, RGB output, fastblanking, etc.) is shared with the microcontroller.
SYSTEML/L'BG/L
BG
I
DK
L
L'
LLL
LLH
LLL
LHL
HHL
I
5
Small signal
IC 7015 (TDA836X) is a single-chip video processor with built in IF- detector, luminance and chrominance separator, PAL chroma
decoder, RGB processing , horitzontal&vertical syn. processor, FM sound- decoder,
IF (INTERMEDIATE FRECUENCY) DEMODULATION (ic7015/6A)
IC 7015/6A contains the IF detector. The 38.9 MHz IF signal is a present at the output pin 11 of the tuner (33.4 MHz for a sign al
according to the SECAM L' system).
Bandpass filter; The IF bandpass characteristic is determinated by the bandpass of the SAW (Surface Acoustic Wave) filter 1015.
* For PAL BG sets a SAW filter with 5.5 MHz bandwich is used (33.4 to 38.9 MHz).
* For PAL I sets a SAW filter with a bandwinch of 6.0 MHz is used (33.4 to 39.4 MHz).
* For PAL BGI/SECAM BGLL' sets a SAW filter with 6.0 MHz bandwich is used to enable BGILL' reception.
* For LL' reception BG/L is "high", D6014 conducts and so the 33.4 MHz is tuned to a lower frecuency with C2014 (32.9 to 38.9 MHz).
* For BGIDK reception BG/L is "low", D6014 does no conduct. With C2013 the bandpass filter is tuned at 33.4 MHz (32.4 to 38.9
MHz).
* For PAL BG/SECAM BGDK sets a SAW filter with a bandwich of 6.5 MHz is used without switching possibilities (32.4 to 38.9
MHz).
Demodulation and AGC; After the bandpass filter the IF signal is supplied to the IF-detector IC7015/6A pins 45 and 46. This IC7015
6A is suitable for a both negativ e (BGIDK) and positive (LL') modulation controlled b y the BG/L s witching signal (" high" for LL' positive
modulation, "low" for a BGDIK negative modulation) at pin 1 IC7015/6F (pin 1 IC7015/6F is at DC level input pin for positive/negative
switching of IC7015/6A). This control also determinates whether the AGC circuit controls at the top white le vel (positive modulation) or
at the top sync level (negative modulation).
The high-frecuency AGC voltage is available at pin 47. The take over level of the high-frecuency (delayed) AGC control can be set at
pin 49 by means of R3021. For switching to diferent IF for the SECAM L' system (33.4 MHz) the demodulation reference circuit 5040
at pins 2 and 3 IC7015/6A is switched by switching signal L/L'.
* For BGILDK reception L/L' is "low", D6042 conduct and so coil 5043 is connected in parallel to 5040. The circuit is tuned to 38.9
MHz.
* For reception L/L' is "high", D6042 does nor conduct. The circuit is tuned to 33.4 Mhz by L5040 only.
Note: For sets with LL' reception L5040 is tuned at 33.4 MHz, for sets without LL' reception L5040 is tuned at 38.9 MHz (or 39.5
MHz for PAL I only sets).
Automatic Frecuency Control (AFC) signal at pin 44 is obtained from the reference signal of the IF-detector and the control is
modified internally in IC7015/6A for positive or negative modulation. C2037 smoothes the AFC voltage.
SOURCE SELECT, LUMINANCE AND CHROMINANCE SEPARATION (IC7015/6B)
Sound trap; The baseband CVBS signal of pin 7 IC7015/6A (nominal amplitude of 2Vpp) also contains the 5.5 or 6.0 MHz FM sound
signal (FM intercarrier sound). This sound signal is filtered out with a 5.5 MHz (6.0 MHz PAL I) ceramic filter (1032 and/or 1033).
Source select: The CVBS signal is now fed to pin 13 IC7015/6B to the source selector switch in IC7015/6B. Pin INT/EXT = 0V gives
internal CVBS (pin 13), pin 16 INT/EXT = 8V gives external CVBS (pin 15) (external signal SCART CVBS IN from the CVBS IN cinch
or pin 20 scart-connector).
Luminance and chrominance separation: chrominance signal is filtered out (-20dB) by a luminance notch filter which is internallly
calibrated at the subcarrier frecuency (4.43 or 3.58). The IDENT status signal is coming from pin 14 IC7015/6B. In case of no
horizontal sync (so no signal detected) by the sync processor IC7015/6E, pin 14 IC7015/6B is made "low", TS7651 does not conduct
so pin 16 of the µC is "high". The IDENT signal is internally fed to ensuring stable OSD even without transmiter signal (IC7015/6D can
be switched to different time constants).
CHROMINANCE DECODING (IC7015/6C)
CVBS is extracted from the baseband CVBS signal from the IF-detector via crystals 1032. PAL (and NTSC if applicable) chroma
decoding inside IC7015/6C, SECAM chroma decoding inside IC7250.
Inside IC7015/6C the PAL (or NTSC) chroma signal is fed via amplification and a burst demodulator to the R-Y and B-Y demodulator.
(PAL or NTSC processing is deter mined automatically by the burst demodulator inside IC7015/6C). The 4.43 MHz reference crystal
for chrominance demodulation in IC7015/6Cis in present at pin 35 of IC7015/6C.
Pin 27 shoud be 5V5 (via R3280) to force IC7015 in the PAL/SECAM mode; by then IC7015/6C is in the PAL decoding mode and via
pin 27 feeds throught the chroma signal to the SECAM chroma decoder IC7250 (so IC7015/6C searches for PAL and IC7250
searches for SECAM).
bidirectional communication line between pin 32 of IC7015/6C and pin of IC7250 both IC7015/6C and IC7250 "know" wether
Via a
a PAL or a SECAM signal is detected:
- On AC level there is a
- On DC level there is a SECAM or PAL switching line enabling automatic selection of IC7015/6C and IC7250 to supply R-Y and BY to the delay line IC7271.
* If IC7015/6C has detected a PAL signal,
IC7015 / 6C are fed to delay line IC7271.
* If IC7015/6C has detected a PAL signal, Vpin 32 is made 5V. By then the demodulated R-Y and B-Y at output pins 30 and 31 of
IC7015/6C are not fed to the delay line IC7271.
* If IC7250 has detected SECAM
case the sinking current at pin 32 IC7015/6C is typical 150 µA, only by then IC7015/6C "knows" IC7250 has detected SECAM
demodulated R-Y and B-Y are fed to the delay line IC7271 via output pins 9 and 10 of IC7250.
4,43 calibration for calibration of thr PLL and chroma cloche filter of IC7250.
Vpin 32 is made 1V5. By then the demodulated R-Y and B-Y at output pins 30 and 31 od
Vpin 1 IC7250 becomes "low", sinking typical 150 µA from the 5V from pin 32 IC7015/6C. Only in
6
RGB DEMATRIXING (IC7015/6D)
RGB-dematrixing dematrixies the -(R-Y), -(B-Y) and the Y signals; the sandcastle pulse coming from the IC7015/6E synchronises
RGB dematrixing and suppresses the RGB signals during line and frame flyback.
Control by µC for contrast, brightness and saturation (0V5 to 4V5).
RGB-source select switches between internal RGB and external RGB (OSD or SACART) via pin 21 of IC7015/6D (via resp OSD
FAST BLANKING from OSD generator and FAST BLANKING from SACART or µP INT/EXT from µC).
HORIZONTAL SYNCHRONISATION (IC7015/6E) diagram B
Start up of the hor. oscillator via +11A giv es start up current into pin 36 5V8 the hor . oscillator starts running approx. 25 KHz and only
when IC7015 supply pin 10 = 8V the line frecuency changes to 15625 Hz.
Hor, sync., separator separates hor pulses out of CVBS and so synchronises the free-running hor. sawtooth generator. Both the line
and frame frecuencies are internally locked to the chroma oscillator on pin 35 IC7015/6C.
Hor, oscillator sawtooth is converted in square wave voltage with variable duty cycle (pin 37). Hor, flyback pulse at pin 38 compares
phase of flyback pulse with phase of the hor. oscillator ; if phase not correct the duty cycle of hor. oscillator will be adjusted. Time
connstant of the sync. circuit automacallly determinated by IC7015/6E. Pin 38 is both sandcastle output and hor. flyback input.
Selection automacally determinated by the input current (sandcastle a few µA, flyback 100-300 µA determinate by R3371).
Amplitudes of sandcastle pulse; burst 5V3, line blanking is 3V, frame blanking 2V.
At standby (STANDBY "low") TS7580 blocks and TS7581 conducts and so the line is shut down at stand by.
VERTICAL (VERT.) SYNCHRONISATION (IC7015/6E) diagram B
Vert. sync. separator separates frame sync. pulses from CVBS and so synchronises frame oscillator. IC7015/6E compares phase of
flyback pulse with phase of sawtooth at pin 42 (from external RC network); if phase not correct the duty cycle of hor. Pre-amplifier in
IC7015/6E amplifies sawtooth (pin 43 of IC7015/6).
increases (more white), EHT decreases so picture will become too big. BCI and so BCI' decrases for increasing beam current
(diagram C) and the picture will be corrected.
SOUND DETECTION (IC7015/6F) diagram D
There are two audio paths: for the BG, I and DK systems FM modulated intercarrier sound (sound extracted from baseband CVBS
from IF detector), for the LL' systems AM modulated quasi-split sound (sound extracted directly from the tunner).
FM demodulation; For FM modulated sound the sound signal is filtered throught filter 1135 or 1136 from the baseband picture si gnal.
For BGDK or BGILL' sets the switching signal BG/I is used to select the current crystals.
* For I (or DK) reception BG/I is "low", TS7170 does not conduct, D6170 conduct and so crystal 1136 (6.0 MHz for I and 6.5 MHz for
DK) is switched parallel to 1135.
* For BG reception BG/I is "high", TS7170 conduct, D6170 does not conduct and 1136 is not switched in parallel to 1135 (5.5 MHz
only).
* For PAL BG or PAL I only sets only 1135 is used (resp. 5.5 MHz or 6.0 Mhz). FM-mono sound demodulation takes place in
IC7015.6F. No adjustament required for BG or I demodulation as automatic PLL tuning (4.2 to 6.8 MHz).
Sound frecuency characteristic is defined by de-emphasis C2112 at pin 1. Volume control on DC level at pin 5. Selection between
FM sound or AM sound/EXT sound (from input pin 6) by pin 16 IC7015/6B.
AM demodulation; Interferences signals at 30,9 MHz are removed from IF signal coming fron tuner by SAW filter 1137 (double band
pass caracteristic) the required frequency spectrum is fed to the AM demodulation IC7125. The doble characteristic is necessary
because for the L system the sound is at 32,4 MHz and for L´at 39,9 switched by switching signal L/L´and TS 7126 TS7127
* For L´ reception (L/L´ is "high") IF signal is present in pin 2.
* For L reception (L/L´ is "low") IF signal is present in pin 1.
The demodulated signal at pin 6 of IC7125 is supplier to the source selection switch in IC7140 , C2126 and 2127 are AGC related
storage capacitos.
Source selection: INT/EXT is "low " for internal and "high" for external . This signal is made from uP INT/EXT and pin 8 of the scart. If
one of these 2 signals is "high" external is selected. BG/L is "low" for FM sound (BGIDK) and "high" for AM sound (LL').
* Top switch in IC7140 select between AM sound (pin 5) and EXT sound from SCART +AV (pin3) by pin 9 INT/EXT. The output of this
selector (pin 4 IC7150 ) is fed to input pin 6 of FM demodulator IC7015/6F .
Here selection is made between FM sound (pin 5) and EXT sound from SCART+ AV (pin 3) by pin 9 INT/EXT. The output of this
selector (pin 4 IC7150) is fed to input pin 6 of FM demodulator IC7015/6F.
* Middle switch in IC7140 selects between AM (pin 1) and FM sound (pin 2) for SCART AUDIO OUT by pin 10 (BG/L is "high" for AM
pin1, "low" for FM pin2).
* Bottom switch in IC7140 connects +8 to pin 1 IC7015/6F to switch the IF-detector and AGC (both IC7015/6A) to positiv e modulati on
for SECAM LL´(BG/L so pin 11 IC7140 is "high" for AM LL´ positive modulation so pin 13 to +8).
Anti-plop; At switch on the set C2183 is not charged, anode C2183 is "high", TS7183 conducts and so mutes the output amplifier
IC7187. As soon as C2183 is charged anode C2183 is "low", TS7183 stops m uting.
At switch off of the set the +8A drops very fast. As C2183 is still charged, the anode of C2183 becomes approx. -8V DC. By then the
DC volume control signal VOLUME is shorted via zener D6183, so IC7015/6F is muted.
Via BCI' frame correction is realised for high beam currents; If beam current
7
Power Supply
Mains isolated switched mode power supply (SMPS), control IC7514 (TDA4605) gives oscillation, variable frequency, variable duty
cycle, switching FET, no opto coupler, no thrystor switching windings on the secondary side, slow start circuitr y and no standby
mode of the power supply. Via sense windings 4-2 frequency and duty cycle control on the primary side.
Duty cycle and frequency of the power depends on T-on of FET TS7525 which is controlled by IC7514. This IC detects variations
of the +100 (at the secondary side of 5525 at winding 5-7) via sensing windings 4-2 at the primar y side of 5525. The switching
period of TS7525 is divided in three main areas T-on, T-off and T-dead:
During T-on energy is extracted from the mains into the primary winding 8-12 of transformer 5525 with a linear increasing primar y
current (slope depends on voltage across C2505). Via T-on regulation the duty cycle and the frequency of the SMPS and so the
+100 can be controlled.
During T-off energy "inside" transformer is supplied to the load via secondary windings of 5525. Current through secondary side of
the transformer decreases linear with firm slope.
During T-dead no energy is extracted or supplied. During T-dead the L-prim is demagnetised (polarity L-prim and C2524 is switched).
PRIMARY SIDE
Degaussing; R3501 is a dual PTC (2 PTC's in one housing). After switch on set, PTC is cold so low-ohmic and so degaussing
current is very high. After degaussing, PTC is heated so high-ohmic, so in normal operation degaussing current very low.
Mains voltage is filtered by L5500, full wave rectified by diodes 6502-6505 and smoothed by C2505 to VIN (300 V DC for 220V AC
mains).
Start up; Via start up circuitry via R3507 the DC voltage VIN is used to start up IC7514. As soon as the supply voltage Vpin6 12V
the IC7514 starts; the internal oscillator of IC7514 drives TS7525 into conduction at the lowest frequency (during start up C2523
determines the frequency; as C2523 is uncharged at start up this gives a low start). The power supply automatically starts up.
Take over IC7514; During start up a voltage across winding 4-2 is built up. At the moment the voltage across winding 4-2 reaches
approx. +15V, D6521 star ts conducting and takes over the +15 supply voltage at pin 6 IC7514.
CONTROL CIRCUITRY
+100 feedback for frequency and duty cycle control; Sense windings 4-2 has same polarity as winding 5-7. During T-off winding 57 and so winding 4-2 are positive. D6515 conducts and so charges C2515; the DC level across C2515 is a reference for the +100.
Via R3518, R3517 and R3508 this DC-voltage is brought to the required level for input pin 1 IC7514; this voltage is used for
frequency and duty cycle control of IC7514.
R3518 is a potentiometer and so +100 can be adjusted.
IC7514 controls +100 by controlling T-on and so the frequency and the duty cycle; IC7514 compares v oltage at pin 1 with an internal
reference voltage.
* In a stable situation the voltage at pin 1 is the same as the internal reference voltage, so frequency and duty cycle remains the
same.
* If +100 increases the voltage at pin 1 increases, and so the frequency and duty cycle and so the +100 will be decreased (new
balance of voltage at pin 1 and the reference voltage and so new lower stable frequency and duty cycle).
* If +100 decreases, the voltage at pin 1 decreases. The frequency and duty cycle and so the +100 will be increased.
The voltage at pin 1 is in a stable situation typical 400 mV.
Undervoltage protection; If Vpin6 supply voltage drops under 7V25, the logic in IC7514 will shut the output at pin 5. The power
supply will stop running.
Overvoltage protection; The power at pin 3 IC7515 is a measure for the mains voltage and so the DC Vin across C2505. As soon
as the voltage Vpin3 6V6, the logic in IC7514 will shut the output at pin 5. The power supply will stop running.
Overload protection; If the secondary load becomes too high, the T-on becomes too long. The internal sawtooth used for oscillation
is measured over C2509 at pin 2 IC7514. If Vpin2 3V (foldback point) the IC will switch into overload mode giving protection (hickup or burst mode): IC7514 switches TS7525 and so power supply "off" as long as I-prim is too high, starts up again, if I-prim still
too high switches "off" again, etc.
SECONDARY SIDE
±100 for the line output stage ±100A for the tunning (V VARI), +11 for sound output amplifier, +11A for start up of the line circuitry,
±5 for pull up and +5A for µC and EEPROM. No secondary protections are available.
8
Power supply signals
9
Electrical adjustments
Adjuntaments on the main panel (fig.7.2).
1.1. +100V power supply voltage.
Connect a voltmeter (DC) across C2530.
Adjust R3518 for a voltage of +101V5 f or 14" or +106V5
for 20" sets at back picture (beam current 0 mA).
1.2. Horizontal centring.
Is adjusted with potenciometer R3354.
1.3. Picture height.
Is adjusted with potenciometer R3410.
1.4. Focussing.
Is adjudted with potenciometer in the line output
transformer.
1.5. If filter (only for sets with SECAM LL' reception
possibility).
Connect a signal genetor (e. g. PM5326) viaa
capacitor 5p6 to pin 17 of the tunner an adjust the
frequency for 33.4 MHz.
Connect an osciloscope to pin 1 of filter 1015.
Switch on the set and select a program with system
Europe (BG/L "low" for BGIDK reception).
Adjust L5040 for a minimum amplitude.
1.6. AFC.
a. For a sets
Connect a signal generator (e. g. PM5326) as indicated
in point 1.5. Connect a v olmeter to pin 44 of IC7015/6A.
with SECAM LL' reception possibility:
1.7. RF AGC.
If the picture of a strong local transmiter is reproduced
distorted, adjust potenciometer R3021 until the picture
is undistorted.
Or: Connect a pattern generator (e. g. PM5518) to the
aerial amplitude=1mV.
Connect a multimeter (DC) at pin 5 of tunner.
Adjust R3021 so that voltage at a pin 5 of tuner
is 3V7 ±0V5(DC).
2.Adjustaments on the CRT panel (Fig. 7.1).
2.1. Vg2 cut-off points of picture tube.
Apply a pattern generator (e. g. PM5518) and a set it
to a white raster pattern.
Adjust contrast and Vg2 at minimum (Vg2 with
potentiometer in the line output transformer to the left).
Adjust brightness until the DC voltage across
potentiometer 3213 is 0V.
Adjust R3207 (B), R3220 (G) and R3234 (R) for a
black le vel of 115V on the collectors of transistors 7205,
7218 and 7227.
Adjust Vg2 potentiomete until the gun that first emits
ligth is just no longer visible. Adjust the two other guns
with the respective controls (3207 3220 or 3234)
until just no light will be visible.
2.2. Grey sacle (white D).
Apply a test pattern signal and the set for normal
operation. Allow the set to warm up for about 10
minutes.
Adjust R3213 and R3214 until the desired grey scale
has been obtained.
Adjust the frecuency for 38.4 MHz and a select a
program with system France (L/L' is "higt" for
reception).
Adjust L5040 for 3V5 (DC).
Next adjust the frecuency for 38.9 MHz. Select a
program Europe (L/L' is "low" for BG- ILDK reception).
Adjust L5043 for 3V5 (DC).
b. For sets without SECAM LL' reception possibility:
Connect a signal generator (e. g. PM5326) as indicated
above and adjust the frecuency for 38.9 MHz (for a
PAL I at 39.5 MHz). Connect a voltmeter to pin 44 of
IC7015/6A.
Adjust L5043 for 3V5 (DC).
FIG. 7.1
10
Repair facilities
Test points
The CTN chasis is equipped with test points, TP1, TP2, etc
in the service printing on the component side of the
monoboard.
Using these test points it is possible to set a quick diagnosis
on the top of the monoboard.
Functional blocks
On both the service printing on the copper and the component
side, functional blocks are given. These blocks indicate the
functionaly of that specific part of the circuit.
Service Default Mode
The CTN software contains a "Service Default Mode" .
To activate this mode the ser vice pin of the microcomputer
(pin 7-IC7600) should be short-circuited to ear th while
switching on the set with the mains switch (shorting pin 7
can be done on the copper side via the 2 copper squares or
on the component side by pin 7 and the shielding of the µC)
When the set in the Service Default Mode and "S" appears
on the screen.
In the Service Default Mode the set is in a pre-defined mode
In this mode all analog settings (volume, contrast, brighness
and saturation) are in the mid position and the set is tuned to
program number 1.
The Service Default Mode is left via switching off the set by
the mains switch or via standby on the remote control.
Error messages
The microcomputer also detects errors in circuits connected
to the I2C (Inter IC) bus. These error messages are
communicated via OSD (On Screen Display) and a flashing
LED.
ErrorError Possible defect-
message description tive component
F1 en OSD yError interno µCIC7600
LED parpadea
F2 en OSD yError EepromIC7685
LED parpadea
Note: After replacing the microcomputer first solder the
shielding before testing the set. This is needed as the
shielding is used for earth connection.
If this is not done the set can switch into protection mode
(see description of the SMPS).
FIG.7.2
11
Block diagram power supply
+100
+100
+10V
+100
12
List of abbreviations
µCMicrocomputer
µP INT/EXTSwitching signal from µC to TS7876 and TS7877 (diagram C) making together with pin 8 of SCART connector the INT/EXT s witching signal; "low" for
AFAlter nating Current
AFCAutomatic Frecuency Control
AGCAutomatic Gain Control
AMAmplitude modulation
AQUAAquadag on the CRT panel for spark gaps and used for making BCI signal
AVAudio and Video cinches on the rear side of the set
BCIBeam Current Info; if beam current increases the BCI signal decrases. BCI is used for contrast reduction if beam current is too high
BCI'Derived from BCI; if beam current increases (more white), EHT decreases so picture will become too big. BCI and so BCI' decreases for increasing
BG/ISwitching signal from µC; "low" for I or DK reception (6.0 or 6.5 MHZ FM sound), "high" for BG reception (5.5 MHZ FM sound)
BG/I/DK/LL'Sond system BG/I/DK/LL' indicate frecuency distance between sound and picture carriers (5.5 MHz for I, 6.5 MHz for DK and LL')
BG/L
BRIBrightness control signal (same as BRIGHTNESS)
BRIGHTNESSControl signal (from µC, but on DC level via RC network) for brightness control of the video controller IC7015/6D
BSW1Bandswitcing signal from µC to 2 to 3 decorer IC 7002
BSW2Bandswitching signal from µC to 2 to 3 decorer IC7002
CONTRASTControl signal (from µC, but on DC level via RC network) for brightness control of the video controller IC7015/6D
CRTPicture tube
CVSColour Video Blanking Synchronisation from pin 7 IF detector IC7015/6A
DCDirect current
EEPROMElectrical Eresable Programmable Read Only Memory
EHTExtra High Tension (25 KV)
FETField Effect Transistor
FFFilatement (heather voltage)
FMFrecuency MOdulation
HOR FLYBACKHorizontal flyback pulse (15625 Hz) used for locking the horizontal oscillator in IC7015/6E and for locking the OSD generator in the µC
HORHorizontal drive signal from IC7015/6E to line output stage
HUETint ajustment for NTSC system
2
CDigital Control bus of the microcomputer
I
IDENTStatus signal; "low" for horizontal synchronisation, "high" in case horizantal synchronisation is detected
IFIntermediate Frecuency
iNT/EXTSwitching signal derived fromµµP INT/EXT and pin 8 of SCART to pin 16 IC7015/6B and IC7140 (diagram D); "low" for internal, "high" for external
L/L'Switching signal from µC; "low" for BGIDKL (picture at 38.9 MHz) reception, "high" for L' reception (picture at 33.4 MHz)
LEDLight Emitting Diode
LOTLine Output Transformer
MUTE PROG 0Only for sets whithout SCART + AV ; "low" for program 0 muting the sound, "high" for program 1-39
NILNon InterLace
NTSCNational Television System Committee
OSDOn Screen Display
OSD FAST BLANKING Fast blanking info from OSD generator in µC to video controller IC7015/6D for blanking the RGB info to enable OSD-G insertion
OSD-GGreen info from OSD generator in µC to video controller IC7015 for inserting green OSD info on screen.
PALPhase Alter nating Lines
PLLPhase Locked Loop
PORPower On Reset (ensures the µC starts up it's software only if the power supply of the µC itself is high enough)
POS/NEGSwitching signal from IC7140 via BG/L; "high" for positive modulation (LL'), highihmic for negative modulation (BGIDK).
PPPersonal Preference
PROTProttection signal from frame IC7400; in case vertical flyback generator in IC7400 is not activted, the voltage at pin 8 IC7400 becomes 2V.
PTCPositive Temperature Coefficient Resistor
RC5Remote Control 5 system
RGBRed Green Blue
ROMRandom Access Memory
SATURATIONControl signal (from µC, but on DC level via RC network) for saturation control of the video controller IC7015/6D
SAWSurface Acoustic Wave; very precise bandpass filter.
SCSandcastle signal from IC7015/6F to delay line IC7271 and SECAM chroma decoder IC7250
SCART CVBS INCVBS signal from pin 2 SCART to external input pin 15 IC7015/6B
SCART CVBS OUTCVBS signal from IF detector IC 7015/6A to pin 19 SCART
SCART AUDIO INAudio signal from SCART + AV cinches to source select IC7140
SCART AUDIO OUT Audio signal from IC 7140 to pin 1 and 3 SCART + AV
SCARTEuroconnector
SCLClock line of the I²C-bus
SDAData line of the I²C-bus
SDMService Default Mode; predefined mode for faultfinding (see chapter 8)
SECAMSEquential Couleur A Memoire
SMPSSwitched Mode Power Suplly
STANDBYSwitching signal; "low" for standby (only line is shut), "high" for normal operation
SYNCSynchronisation
TP-1Tets point 1
UHFUltra High Frecuency band from tuning range
V-INThe DC voltage across C2505 present at pin 11 of the primary side of the transformer
V-VARITuning voltage (0-30V)
VERT FEEDBLACK50Hz vertical flyback pulse used for locking the vertical oscillator in IC7015/6E
VERT FLYBACK50Hz vertical flyback pulse from frame IC7400 lo lock the OSD generator in µC
VERT DRIVEVertical drive signal from IC7415/6E to frame amplifier IC7400
Vg2Voltage on Grid 2 of the picture tube
VHFVery High Frecuency band from tuning range
VOLUMEControl signal (from µ C, but on DC level via RC network) for volume control of sound processing in IC7015/6F
VSTVoltage Synthesized Tuning
YLuminance part of video signal
internal, "high" for external
beam current (diagram C) and the picture will be corrected.
Switching signal from µC; "low" for BGIDK reception (negative modulation, FM sound), "high" for LL' reception (positive modulation, AM sound)
Protection circuit in IC7400 will make pin 7 "high" overrulling the HOR FLYBACK and SANDCASTLE. The constant "high" sandcastle is supplied to
the luminance circuit and so the picture will be blanked.
13
Electrical Instructions
A. ADJUSTMENT OF MAIN PLATE
1. Supply voltage: +100V.
Connect a voltmeter (DC) between the +2530 and mass. With
potentiometer 3518, adjust voltage to 101V5 for a 14” tube and 106V5
for a 20” or 21” tube.
2. Horizontal centring
Adjust with potentiometer 3354.
3. Picture height
Adjust with potentiometer 3410.
4. Focus adjustment
Adjust with the potentiometer placed on the line transformer.
5. APC
Connect a signal generator (e.g., PM 5326) as indicated in Fig. 1 and
adjust the frequency to 38.9 MHz. (PAL I: 39.5 MHz). Connect a voltmeter to pin 44 of IC 7015:C and adjust voltage with 5040 to 3.5V
(DC).
6. AGC - RF
When the image of a powerful local TV station is distorted, adjust with
potentiometer 3021 until the problem is solved.
B. ADJUSTMENTS ON PICTURE TUBE PANEL
1. Tube cutoff (Voltage Vg 2)
Connect a picture white signal to the antenna.
Connect pin 25 of IC7015:E to mass.
Adjust the brightness until the DC voltage on potentiometer 3214 is
zero.
Using potentiometers 3234, 3207 and 3220, adjust the level of black
on the collector of transistors 7227, 7205 and 7218 to 125V for a 14”
or 21” tube, 130V for a 20” tube.
Adjust potentiometer Vg2 until the light from the gun that comes on
first is barely visible.
Adjust the other two guns with the other controls (3234, 3207 or 3220)
until the light disappears.
2. Grey scale
Connect the test signal to the antenna and adjust TV controls as normal.
Let the TV warm up for at least 10 minutes. Adjust 3214 and 3213
until the desired grey scale is achieved.
PURITY AND CONVERGENCE ADJUSTMENT
NOTE:
The instructions for adjusting colour purity and convergence de
scribed below should be used only if the tube is replaced or when
full adjustment is necessary in any other cases. Even when the
deflection yoke is replaced, it is not necessary to move the rubber
wedges (“G” in Fig. 3). Small corrections can be made using the
multipole unit.
I. Colour purity. (Fig. 3)
1. Slightly loosen screw “F” (if CRT has a multipole unit).
2. Move the deflection coil and remove the three rubber wedges (“G”).
3. Slide the deflection coil as far as possible against the tube bulb and
tighten screw “F” so that the deflection coil can be moved with a
certain amount of resistance.
4. Position the multipole unit as shown in the diagram, tighten screw
“A” and turn safety ring “B” anticlockwise.
5. Place the TV facing either EAST or WEST and insert tube.
Connect a single crosshatch signal to the antenna and turn up the
brightness as high as possible. Let the TV warm up for 10 minutes.
6. Adjust the static convergence using tabs “C” and “D” (see Chapter
II if necessary).
7. Block the green and blue guns by disconnecting resistors 3216
and 3203, respectively.
8. Tur n the colour purity rings with tab “E” so that the vertical red line
coincides as closely as possible with the centre of the screen and,
at the same time, make sure the centre horizontal line is as cor
rectly aligned as possible.
9. Connect a picture white signal and make sure the red vertical line
is in the centre of the screen. If it is not in the centre, connect the
crosshatch signal again and move the red vertical line in the right
direction, making sure that the image does not stray too far from
vertical.
10.Connect a picture white signal and move the deflection coil until
the inside of the screen is uniformly red.
11.Connect the green and blue guns and make sure that no spots
appear on the white screen obtained. If spots appear, they can be
corrected by turning rings “E” and/or moving the deflection coil.
12. Tighten screw “F”.
13. Now adjust the static and dynamic convergence.
II. Static convergence (Fig. 3).
(If CRT has a multipole unit)
1. Connect a crosshatch signal and let the TV warm up for 10
minutes.
2. Block the green gun by disconnecting 3216 and turning attachment
ring “B” anticlockwise.
3. Turn the 4-pole magnetic rings with tab “C” so that the blue and red
crosshatch pattern is superimposed in the centre of the screen.
4. Connect the green gun and disconnect the blue gun by disconnect
ing resistor 3203.
5. Turn the 6-pole magnetic rings with tab “D” so that the red and
green crosshatch pattern is superimposed in the centre of the
screen.
6. Connect the blue gun and set the multipole unit using ring ”B”.
III. Dynamic convergence
NOTE:
Dynamic convergence is obtained by moving the deflection coil hori
zontally and vertically. In order to ensure the exact position of the
deflection yoke, three rubber w edges are placed between the glass
of the tube bulb and the deflection coil as shown in Fig. 4a or 5d.
1. First adjust colour purity and static convergence.
2. Connect a crosshatch signal and disconnect the green gun by dis
connecting resistor 3216.
3. Eliminate the central, horizontal and vertical blue and red lines by
moving the deflection coil vertically. If the position of the deflection
coil is correct, place the rubber wedge (1) either straight up (Fig.
4a) or straight down (Fig. 5a).
The placement of the wedge as in Fig. 4a is correct if the deflection
coil is facing down.
4. By moving the deflection coil horizontally, the horizontal red and
blue line is superimposed in the top and bottom of the screen and
the red and blue vertical line to the left and right. If the position of
the deflection coil is correct, place wedges (2) and (3) as shown in
Fig. 4b or 5b. Firmly press the adhesive part of the wedge against
the tube glass.
5. Now place wedge (4) as in Fig. 4c or 5c and press so that it adheres
to the tube.
6. Remove wedge (1) and place it as shown in Fig. 4d or 5d.
7. Connect the green gun.
14
15
Safety instructions, maintenance instructions,
warning and notes
Safety Instructions for Repairs
1. Safety regulations require that during a repair:
- The set should be connected to the mains via an isolating
transformer.
- Safety components, indicated by the symbol should be
replaced by components identical to the original ones
- When replacing the CRT, safety goggles must be worn.
!
2. Safety regulations require also that after a repair:
- The set should be returned in its original condition.
- The cabinet should be checked for defects to avoid touching, by
the customer, of inner parts.
- The insulation of the mains lead should be checked for external
damage.
- The mains lead strain relief should be checked on its function
- The cablef orm and EHT cable are routed correctly and fix ed with
the mounted cable clamps in order to avoid touching of the CRT,
hot components or heat sinks
- The electrical resistance between mains plug and the secondary
side is checked. This check can be done as follows:
· Unplug the mains cord and connect a wire tween the two pins
of the mains plug.
· Switch on the TV with the main switch.
· Measure the resistance value between the pins of the mains
plug and the metal shielding of the tuner or the aerial
connection on the set. The reading should be between 4.5 M
and 12 M.
· Switch off the TV and remove the wire betw een the two pins of
the mains plug.
· Thermally loaded solder joints should be oldered.
-This includes components like LOT, the line utput transistor, flyback capacitor.
Maintenance Instructions
It is recommended to have a maintenance inspection carried out
periodically by a qualified service employee.
The interval depends on the usage conditions.
- When the set is used in a living room the recommended interval
is 3 to 5 years. When the set is used in the kitchen or garage this
interval is 1 year.
- During the maintenance inspection the above mentioned "safety
instructions for repair" should be caried out. The power supply
and deflection circuitry on the chassis, the CRT panel and the
neck of the CRT should be cleaned.
Warnings
1.In order to prevent damage to IC's and transistors any flash-over of
the EHT should be avoided. To prevent damage to the picture tube
the method, indicated in Fig. 11.1., has to be applied to discharge
the picture tube.
Make use of an EHT probe and a universal meter is 0V (after approx
30s).
2. ESD.
All IC's and many other semi-conductors are sensitive to electrostatic
discharges (ESD). Careless handing during repair can reduce life
drastically. When repairing, make sure that you are connected with
the same potential as the mass of the set via wrist wrap with
resistance. Keep components and tools on the same potential.
3. Proceed with care when testing the EHT section and the picture
tube.
4. Never replace any modules or any other parts while the set is
switched on.
5. Use plastic instead of metal alignment tools. This will prevent any
short circuits and the danger of a circuit becoming unstable.
6. Upon a repair of a transistor or an IC assembly (e.g. a transistor or
IC with heatsink and spring) remounting should be carried out in
the following order:
1. Mount transistor or IC on heatsink with spring.
2. Resolder the joints.
Notes
1. After replacing the microcomputer first solder the shielding before
testing the set. This is needed as the shielding is used for ear th
connection. If this is not done the set can switch into protection
mode (see description of the SMPS).
2. Do not use heatsink as earth reference.
3. The direct voltages and waveforms should be measured relative to
the nearest earthing point on the printed circuit board.
4. The direct voltages and waveforms are measured in the Service
Default Mode (see chapter 8). Use a colour bar pattern of a pattern
generator (e.g. PM5518).
5. The DC voltages and oscillograms are where necessary measured
with ( ) and without ( ) aerial signal (settings as in Service
Default Mode; see chapter 8).
Voltages and oscillograms in the power supply section have been
measured for both normal operation ( ) and in the stand-by mode
( ). As an input signal a colour bar pattern has been used.
FIG. 11.1
6. The picture tube PWB has printed spark gaps. Each spark gap is
connected between and electrode of the picture tube and the
Aguadog coating.
The small signal is processed by TD A8361, (TDA8360 no scart) for Pal sets and TDA8362 for Pal/Secam
sets (IC 7015), including IF detection, video processing, chroma decoder, RGB processing, sync processor
and FM sound decoder.
1.1- IF detection (IC7015/6A)
- IF input (pins 45,46): The IF signal comes from pin 11 of the tuner to the IF SAW (Surface Acoustic Wave)
filter (1015) and the IF-detector IC7015/6A (pins 45 and 46).
- IF filter (1015): The IF bandpass characteristic, determined by the SAW filter, is 33.4 to 38.9 MHz. for BG
sets, 33.5 to 39.5 MHz. for PAL I sets and 32.4 to 38.9 MHz. for DK sets.
- IF oscillator (pins 2,3): Carrier frequency, present in coil L5040, is tuned at 38.9 MHz. for BG sets or
39.5 MHz for Pal I sets
- AGC voltage (pin 47): The AGC delayed voltage is applied to pin 1 of the tuner. It should be adjusted
for 1mV. antenna signal by means of R3021 (pin 49).
- AFC signal (pin 44): The Automatic Frequency Control is obtained from the reference signal of the IFdetector. C2037 smoothes the AFC voltage.
- Identification (pin 4): The identification output is applied to pin 16 of the µC. This signal is high in case of
signal detected.
- Video output (pin 7) : This baseband CVBS signal with 2Vpp of nominal amplitude, also contains the FM
intercarrier sound signal. Sound is filtered out by a ceramic trap (1032 or 1033) which frequency can be
different depending on the system: 5.5 MHz. for BGLL’, 6.0 MHz. Pal I or 6,5 MHz. for DK.
Multistandard sets
-The IC TDA8362 changes automatically between negative (BGIDK) and positive (LL’) modulation.
The IC also determines if the AGC circuit should control at the top white level of the video (positive
modulation) or at the top sync level (negative modulation).
-Saw filter (1015) bandpass characteristic is modified by BG/L switching signal proceeding from the
microcontroller:
- For BGIDK reception BG/L is low, D6014 does no conduct and the bandpass filter is tuned by
5012 and 2013 at 32.9MHz. to 38,9 MHz.
- For LL’ reception BG/L is high, D6014 conducts and so the bandpass filter is tuned by 5012 and
C2014 at 32.4 to 38.9 MHz.
-Oscillator frequency is controlled by the L/L’ switching signal:
-For BGIL reception L/L’ is low, D6042 conduct and so coil 5043 is connected in parallel to 5040.
- The circuit is tuned to 38.9 MHz.
- For L’ reception L/L’ i s high, D6042 does nor conduct and the circuit is tuned to 33.4 MHz. by L5040 only.
1.2- Source select, luminance and chroma separation (IC7015/6B)
- Source select (pin 13, 15, 16): The internal CVBS signal is now fed to pin 13 IC7015/6B. External CVBS
from the pin 20 of Euroconnector is present on pin 15. The source selector switch between internal (pin 16 = 0V.)
or external (pin 16 = 8V.).
- Luminance and chrominance separation: Chrominance signal is filtered out (-20dB) by a luminance
notch filter which is internally calibrated at the subcarrier frequency (4.43MHz).
1.3- Chroma Decoding (IC7015/6C)
Pal or Secam signals are recognized automatically by the IC. For Pal signals decoding is made in IC7015/
6C and for Secam signals in IC7250 (TDA8395).
- Pal signal: This signal is amplified and demodulated. The 4.43 MHz. reference crystal for chrominance
demodulation is present at pin 35 of IC7015/6C. The R-Y and B-Y out-puts (pins 30, 31) are applied to
chroma delay line IC7221 (TDA4665).
- Secam signal (pin 27): This signal is applied to pin 16 of Secam decoder IC7250.
- Secam reference (pin 32): Pal or Secam signals are recognized using a DC level by bi-directional
26
communication line between this pin and pin 1 of IC7250.
-If IC7015/6C has detected a Pal signal, Vpin 32 is made 1,5V. By then the demodulated R-Y and BY outputs (pins 30, 31) are applied to delay line IC7271.
-If IC7015/6C has not detected a Pal signal, Vpin 32 is made 5V. By then the demodulated R-Y and
B-Y at outputs (pins 30, 31) are not used.
-If IC7250 has detected a Secam signal, Vpin 1 IC7250 becomes low, sinking typical 150µA. current
from pin 32 (5V.) of IC7015/6C, which one detect this current to know that a Secam signal has been
detected. In this case R-Y and B-Y signals are applied to the delay line IC7271 via outputs of
IC7250 (pins 9 and 10).
This bi-directional communication line uses AC level to calibrate the 4,43MHz. between the PLL and chroma
cloche filter of IC7250.
1.4- RGB-dematrixing(IC7015/6D)
- R-Y, B-Y inputs (pins 28, 29): The R-Y and B-Y signals come from delay line (IC7271) and the Y signal
comes (internally) from IC7015/6B.
The sandcastle pulse coming (internally) from the IC7015/6E (pin 38) synchronizes RGB dematrixing and
suppresses the RGB signals during line and frame flyback.
- Video controls (pins 17, 25, 26): These inputs for contrast, br ightness and saturation can be adjusted
from 0,5V to 4,5V by the µC. If beam current is limited reducing contrast with D6289 circuit.
- RGB inputs (pins 22, 23, 24): External RGB inputs come from Euroconnector and are switched by fast
blanking.
- Fast blanking (pin 21): When voltage of pin 21 is 0,4V. internal RGB is used. For a pin 21 voltage between
0,4V. and 3,5V. the set switch to external RGB.
If voltage of pin 21 is 4V. both internal and external are deleted. The up uses this status to insert RGB signals
from OSD generator directly to RGB outputs.
Fast blanking can switch signals for full screen (by a DC voltage) or for a part of the screen (by a pulse
voltage).
- RGB outputs (pins 18, 19, 20): See RGB amplifier.
1.5- Horizontal synchro (IC7015/6E)
- Start up (pin 36): When the set is switched on, voltage at pin 36 rises and when exceeds 7V. the horizontal
oscillator starts running at approx. 25 KHz. (slow start). After the line starts, main supply of IC7015 (pin 10)
comes up to 8V. and the line frequency changes to 15625 Hz.
- Standby (pin 36): This pin is used also for standby function. In this case the voltage is reduced to 3V. by
the uP and so the line is shut down.
- Hor. oscillator: This oscillator is fully integrated and internally calibrated. Frequency is obtained derived of
chroma oscillator on pin 35 of IC7015/6C.
- Hor. sync separator: This circuit (fully integrated) separates hor. pulses of CVBS proceeding from 7051/6B .
- Oscillator synchro (pin 40): Oscillator is synchronized with video signal by a first control loop circuit. The
control voltage is present at pin 39.
- Hor. phase control (pin 39): Line fly-back (pin 38) is synchronized with oscillator by a second control loop
circuit. The control voltage is present at pin 39. Phase can be adjusted by 3354.
- Hor. output (pin 37): Oscillator is converted in square wave voltage at this pin.
- Sandcastle (pin 38): This pin is used as line fly-back input and also as sandcastle output. Levels of
sandcastle pulse are 5,3V for burst detection, 3V. for line blanking and 2V. for frame blanking.
1.6- Vertical synchro (IC7015/6E)
- Vertical oscillator (pin 42): Frequency is obtained dividing frequency of chroma oscillator on pin 35
IC7015/6C. At pin 42 a sawtooth signal is present. Resistor 3342 is used to correct vertical amplitude with
beam current.
- Vert. sync. separator: It separates frame sync. pulses from CVBS and so synchronizes frame oscillator.
- Vert. drive (pin 43): This out-put is used to drive the vertical amplifier (7400)
- Vert. feedback (pin 41): this feedback is proportional to deflection current and is used to correct the vert.
drive signal.
2.- RGB AMPLIFIERS (diagram B)
27
- RGB inputs : The RGB signals available at pins 20, 19 and 18 of IC7015/6D are drived by emitter followers
(7210, 7211, 7212), to RGB amplifiers.
- Reference voltage (7225): An inter nal reference voltage of 2.5V. is produced on the emitter of transistor
7225 to keep the black level stable.
- RGB amplifiers (7205, 7218, 7227): Signal is inverted and drived to the CPT by RGB amplifiers. To
improve high frequency amplification there are small capacitors (2204, 2217 and 2230).
- Flash-over protections: Clamping diodes to +8V. (6203, 6216, 6229) and 1K5 series resistors (3203,
3216, 3229) are added for protect the circuit from CPT flash-over.
- White adjustment: The gain of B and G amplifiers can be adjusted by 3213 and 3214.
- Cut-off adjustment: The black level of the CPT can be adjusted by 3207, 3220, 3234 and Vg2.
3.- SOUND CIRCUIT (diagram C)
3.1- FM Sound detection (IC7015/6F)
- FM input (pin 5): FM sound is extracted from baseband video (CVBS) proceeding of IF detector and
filtered through 1136 (5.5 MHz. for BG sets, 6.0 Mhz. for Pal I sets, 6.5 Mhz. for DK sets).
- FM demodulation: FM - mono sound demodulation takes place in IC7015/6F. No adjustment is required
because demodulation is doing by an automatic PLL (4.2 to 6.8 MHz.).
- De-emphasis (pin 1): Sound frequency characteristic is defined by de-emphasis capacitor C2112 at pin 1.
- External FM audio out (pin 1): The signal at this pin is amplified by T7114 and T7115 to drive the
euroconnector sound outputs (pins 1,3).
- External FM audio in (pin 6): External audio proceeding of euroconnector (pins 2,6) is applied to this pin.
Selection between internal or external is done by pin 16 of IC7015/6B.
This output is drived to pin 3 of the final sound amplifier IC7187 (TDA7052 or TDA7056).
Multistandard sets:
-FM demodulation: This function is done in the same way that no multi sets. The only difference consist
of a second Pal I 6MHz. filter (1135) in addition to the 5,5MHz. BG filter (1136). 6MHz. filter is switched
off for BG reception by transistor 7170 depending on BG/I signal.
-AM demodulation: In Multistandard sets, also AM demodulation for LL’ systems is necessary. AM
sound is extracted directly from the tuner instead of from baseband video.
AM Sound detection (IC7125)
- AM input (pins 1,16): AM signal at 32,4MHz. for L system or 39,9MHz. for L’, is removed from IF
signal coming from tuner by SAW filter 1137 (double band pass characteristic). Sound is switched by
T7126, D6115, TS7127 and D6116 depending on L/L’ signal: For L’ reception (L/L’ is high) IF signal is
present at pin 1, and For L reception, IF signal is present at pin 2.
The required frequency spectrum is fed to pins 1 and 16 of the AM demodulation IC7125.
- AGC (pin 3,5): C2126 and 2127 are AGC related storage capacitors.
- AM Sound output (pin 6): The demodulated signal at pin 6 of IC7125 is supplied to the source selection
switch (pins 1, 5 IC 7140).
AM Sound switching (IC7140)
- External audio out (pin 15): Audio out is selected between AM sound (pin1) or FM sound (pin2) by
internal switch depending on BG/L signal (pin 10).
- Audio in (pins 3, 4, 5): Top switch in IC7140 select between internal AM sound (pin 5) and EXT sound
from SCART (pin3) by INT/EXT signal (pin 9). The output of this selector (pin 4) is fed to input pin 6 of
FM demodulator (IC7015/6F).
- Internal AM audio switching (pin 13): This pin is switched to 8V when the set is in L or L’ system (AM
sound). Then, pin 1 of IC7015/6F is 8V. and this IC switches internally its sound input from pin 5 to pin
6, where AM sound is present. (Sound proceeding from pin 4 of IC7140 can be internal AM or external).
3.2- Sound amplifier (IC7187)
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Sound amplifier can be TDA7052 for 14" and 17" models or TDA7056 for 20" and 21" models.
Amplified sound is drived to the headphones output and loudspeakers. If headphones are connected, loudspeakers
are switched off.
Volume control on DC level is present at pin 4 for TDA7052 or pin 5 for TDA7056.
4.- POWER SUPPLY (Diagram D)
Mains isolated switched mode power supply (SMPS), controlled by IC7514 (TDA4605) in variable frequency
mode.
- Switching behaviour: The switching period is divided in on-time, when energy is extracted from the
mains into the primary winding (8-12 of 5525), off-time, when energy in the transformer is supplied to the
loads via secondary windings of 5525 and dead when no energy is extracted or supplied.
- Standby mode: Output voltages are present when the set is on stand by, due to standby is done cutting
line deflection. On-time is lower and power consumption is very low.
4.1- Primary side
- Degaussing: R3501 is a dual PTC (2 PTC’s in one housing). After switch on set, PTC is cold so lowohmic and so degaussing current is very high. After degaussing, PTC is heated so high-ohmic, so in
normal operation degaussing current is very low.
- Rectifier: Mains voltage is filtered by L5500, full wave rectified by diodes D6502-D6503-D6504-D6505
and smoothed by C2505 (300V. DC for 220V AC mains).
4.2- Control circuit (IC7514)
- Start up and supply (pin 6): When the set is switched on, a current via R3507 is applied to pin 6. Whe n
C2514 is charged to 15V. the power supply starts and a current from pin 5 to T7525 is drived. T7525 and
starts conduction and a voltage across transformer windings is built up. The voltage across winding 4-2 is
rectified by diode D6521 and used to supply the IC on pin 6.
- Soft start (pin 7): The capacitor C2523 causes a slow increase of the duration of the output pulse during
start up.
- IC output (pin 5): This output drives T7525. R3523 is a fuse resistor to protect IC from short circuits in
T7525. D6516 limits the maximum voltage in T7525.
- Start conduction of T7525 (pin 8): A voltage proceeding from winding 4-2 is applied to this pin. The zero
crossing detector recognizes the complete discharge of the energy stored in the transformer core, in addition
to a dead time depending on C2508. This circuit guarantee that T7525 starts conduction at minimum Vds
voltage (see signals 4.5 pag 13).
- Primary current info (pin 2): Current primary winding is simulated by a pin 2 voltage.
- Output voltage info (pin 1): The voltage across winding 4-2 is rectified by diode D6515, divided by
R3527, R3518 and R3508 and applied to pin 1. Internal control voltage (Vcont) inversely proportional to V
pin 1 is generated. Tipical Vpin1 is 400 mV.
- Output regulation (pins 1, 2, 8): IC7514 stabilizes output voltage by controlling T-on and so the frequency
and the duty cycle:
Start pulse to T7525 is determined by pin 8 circuit (see signals 4.5 page 13 ).
Then a sawtood voltage Vpin 2 is generated at pin 2. Stop pulse to T7525 is produced when Vpin 2
reaches Vcont.
Output control is done by the following way:
If output is higher, Vpin 1 is higher, Vcont is lower, T-on and output will be reduced.
If output is lower, output will be increased.
Output voltage of supply can be adjusted by R3518.
Mains voltage variation is stabilized in the following way:
If mains voltage is higher, slope in the sawtood voltage Vpin 2 is higher, stop point is reached before
and T-on is reduced.
If mains voltage is lower, T-on is increased.
4.3- Protections
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- Overload protection (pin 2): This is produced if T-on is increased till Vpin 2 voltage reaches the foldback
point (see signals 4.5). The IC will switch into overload mode (off and on continuously).
- Output voltage protections (pin 6): Limiting values of Vpin 6 voltage (7.25 and 16V.) provide under and
overvoltage protections for the circuit.
- Mains overvoltage (pin 3): The voltage at pin 3 IC7515 is a measure for the mains voltage and so the DC
voltage across C2505. As soon as the voltage Vpin 3 reaches 6.6V. the supply will stop running.
4.4- Secondary side
- Line supply: The value to adjust the supply is 101,5V. for 14" CPT’S, 102,5V. for 17" CPT’S and 107V. for
20"/21" CPT’S. This supply is also used to obtain the +33V. varicap voltage by D6602.
- Auxiliary supply (+11V.): This supply is used for sound output amplifier, for start up the line circuitry and
for the stand by of the microprocessor. +5STB is regulated by T7525 and D6575. A +5V. power on reset
signal (POR) is obtained during star t up by R3573 till T7571 conducts by D6570.
4.5- Power supply signals
V cont
V pin 5 = V GS (7525)
I DS (7525)
V DS (7525)
5.- DEFLECTION (Diagram E)
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5.1- Frame deflection
This function is performed by the integrated circuit TDA3653 (7400).
- Frame supply (pins 6, 8, 9): Pin 9 is used to supply the IC except output stage which one is supplied b y
pin 6. At pin 6 there is a higher voltage during flyback time. This is produced adding the flyback signal
present at pin 8 to a +25V. supply by D6416 and C2415. Pin 8 is also used to drive vertical flyback input at
pin 37 of the up. (IC 7600)
- Vertical input (pins 1, 3): The input circuit is driven by pin 44 of IC7015/6E. Vertical signal is amplified and
inverted.
- Vertical output (pin 5): Ver tical output is applied to deflection coil. DC current is suppressed by C2404. A
voltage proportional to current deflection is present in R3411/12 and a feedback of it is sent to pin 42 of
IC7015/6 by 3407, so that amplitude can be adjusted by 3410. DC feedback is present in R3406. Linearity
is corrected by the network around C2405.
- TRC protection (pin 7): When frame deflection is broken down, the tube is protected blanking all the
picture by pin 7 output.
5.2- Line deflection
The final line transistor is driven by the transformer 5441, whose primary winding is driven by the transistor
T7440 connected to the line drive output of IC7015/6E.
The horizontal deflection stage is carried out in a conventional way, with the deflection transistor (T7445)
and line transformer (5545).
Beam current info (BCI) is present at C2460.
There are the following auxiliary supply voltages obtained from line transformer (5545):
+25V.: To supply frame deflection..
+12V.: To obtain +8V. by IC7016 (diagram A) for small signal, +5V. by T7001 (diagram A) for the tuner
and for the microcontroller.
6.- MICROCONTROLLER/TEXT (Diagram E)
The CTN-BB chassis is designed to accept 2 different microcontrollers: SAA5531 and SAA5541.
Both microcontrollers are mounted in the same position (7600), and the associated circuitry is the same.
The ROM of the ICs contain an specific program that assures all the functions of the appliance, including a
MENU to control the set is (see Instructions Manual).
For no TXT sets SAA5541 is used.
For TXT sets SAA5531 is used which one also contains a teletext decoder, including the following function s:
TXT on/off, reveal, freeze, temporary cancellation, clock, subcode, zoom, index, flof, page +/-, X/26 and 8/
30 packet decoding (station identification and start-up page).
Following there is an explanation of the different functions of the microcontroller indicating pins number
assigned:
- Power supply (pins 31, 39, 44): The IC has several +3,3V power supplies, analog (pin 31), core (pin 39),
and periphery ( pin 44 ). All supplies are present during stand by.
- P.O.R. (pin 43): POR (power on reset) is activated when the set is switched on (see 4.4 pag 13 ). If the
system shows abnormal behaviour it is important to reset it switching off/on the set. Reset can be produced
also connecting pin 43 to +5V. for an instant.
- LED (pin 20): The LED (6663) lights up with a low current when the television set is ON and with a high
current when the set is on Standby. While the set is receiving a remote control signal, the led is blinking.
- RC5 (pin 45): The commands transmitted by the remote control handset are received by infrared receive r
(1685) and passed to the microcontroller for decoding.
- Control keys (pins 10, 11, 12): When a control key is activated, the correspondent pin is connected to
ground.
- I2C bus (pins 49 and 50): The microcontroller is connected to non-volatile memory IC7685 (EEPROM)
31
via bus I2C. Personal preferences (PP) and channel data are stored in the memory. The system can store
79 channels (with the data on tuning voltage and band) and personal preference.
- Service (pin 7): If this pin is connected to earth when the set is switched on, the unit will go into Service
Default Mode (see Repair Facilities in chassis CTN Service Manual).
- Options (pins 14, 21, 52): While start up, the microcontroller checks option pin voltages to know the
special features of this chassis. This one is implemented changing the associated components of these
pins. Different options (menu, multistandard, etc. ) can be seen on tables of diagram E.
- Multistandard out-puts (pins 46, 47, 48): These signals are only used on multistandard units, for
switching the system for decoding sound and video. Signals from pins 46 and 47 are inverted and
set at the correct level by transistors 7672 and 7673, respectively. After they are inverted together
with the signal from pin 48, they make up the system status lines: BG/I is high for Pal I system, BG/
L is high for L and L’ systems and L/L’ is high for L’ system.
- OSD synchronization (pins 36, 37): In order to synchronize the OSD and the TXT information with the
picture signal, the VERT FLYBACK signal (pin 37) and HOR FLYBACK signal (pin 36) are added in inverted
form to the integrated circuit. Due to this if the video signal is lost, the TXT keeps synchronism. - Video
inputs (pins 23 and 24): These inputs are only used on TXT sets. The teletext information is extracted from
the video signal inserted on pins 23 (internal video) and 24 (external video), depending on status of INT/
EXT (pin 8).
- Oscillator (pins 41 and 42): A 12-MHz. oscillator is determined by a 12-MHz. crystal between pins 41 and
42.
- Tuning (pins 1, 9, 16, 51): The unit has a VST (Voltage Synthesized Tuning) system. This system works by
tuning to a station on the tuner through a linear variation of the tuning voltage (V-VARI) from 0V. to 33V.
applied on pin 2 of the tuner. It is generated on pin 1 of the uP and converted to an adequate level for the
tuner using T7605. The AFC signal (Automatic Frequency Control) of IF detector is added to the tuning
voltage V-VARI by R3689 and R3688 to compensate for the slow variation of the tuning feature.
While searching for the station, pin 51 is set on high, which means that the AFC voltage will not be added to
the V-VARI. If an IDENT signal is received on pin 16 while searching for a station, the uP stop searching and
checks via input pin 9 if the tuning is correct and whether the AFC signal can be activated again.
- AGC auto tuning (pin 30): This pin is used to limit the AGC voltage in automatic tuning so that noise
signals are not memorized.
- Band switching (pins 15, 17, 18): There are 3 outputs for band switching pin 15 for VHFI, pin 17 for VHFIII
and pin 18 for UHF. The uP controls the channel band in the tuner by a voltage of +5V. at the correspondent
output.
- Picture and sound adjustments (pins 2, 3, 4, 5, 6): Volume control (pin 2), brightness control (pin 3),
colour control (pin 4), contrast control (pin 5), and sharpness control (pin 6).
The RC networks are used to convert the modulated pulse output to a DC voltage level. These settings can
be pre-programmed in the memory as a personal preference (PP). Mute is controlled internally on the up
during automatic station search or when the signal received is interrupted (detected via the IDENT signal on
pin 16).
- INT/EXT (pin 8): When this output is 0V. the set is switched to external via transistor (7877). This signal is
added to the signal from pin 8 of Euroconnector, so that either of them can be used to switch to external. This
line is also used by the microcontroller as an input line, to switch the adequate video input (internal or
external) used for decoding TXT.
- Standby (pin 19): When this output is high, the set is switched to stand by. The start-up voltage of the
TDA8361A (pin 36) is reduced and the line oscillator stops.
- Fast blanking (pin 35): This pin is used for delete the video picture signal while RGB insertion is produced .
- NIL (Pin 27): This control signal is used (only on TXT sets), to eliminate interlacing for TXT signals. It is
applied to the vertical deflection by switching transistor 7640.
- RGB outputs( pins 32, 33, 34): The RGB outputs are used for On-Screen Display (OSD) and also for
TXT (TXT character set is used for both functions). RGB signals are applied trough common base amplifiers
(7641, 7642, 7644) to RGB outputs of 7015 (pins 20, 19, 18).