Matsui 1410R, Service Manual

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2.- RGB AMPLIFIERS (diagram B)
- 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 internal 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).