Matsui 1410R, Service Manual

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7
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 gives 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). Via BCI' frame correction is realised for high beam currents; If beam current
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 signal.
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 co8 to pin 1 IC7015/6F to switch the IF-detector and AGC (both IC7015/6A) to positive modulation
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 muting.
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.