akira 21WHBN, Service Manual

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8
Model No: 21WHS3BN
Version 1.0
SIGNAL PROCESS
The main chip is N301 TDA9381, AV control switch HEF4052 (video), sound process chip is
TDA9859 (AV audio), sound driver is N601 AN7522N.
The TV signal inputs into the tuner (A201) from CABLE or antenna. The pin 10 and pin 11 of the
N301 are combined to select the band. The pin 4 of the N301 outputs the PWM tuning signal. The IF
video signal comes from the IF pin of the tuner. The 38MHz IF signal is coupled to the V308 (pre-
amplify) and then to SAWF (Z301). After processed in the SAWF, the 38MHz signal gets to the pin 23
and pin 24 of TDA9381. The IF circuit in TDA9381 includes such unit as the AGC amplifying circuit,
38MHz oscillator, PLL video demodulator, video amplifier, IF identify circuit and AFT circuit. The
demodulated signal (CVBS) comes from the pin 38 of TDA9381, the sound signal comes from the pin
44.
The internal CVBS signal needs norm identification then outputs from the pin 38 of TDA9381, via the
trap-wave circuit (composed of the V351, Z351, Z352 and so on) feeds back to the pin 40 of TDA9381.
The RGB signal comes from the pin51, Pin52, Pin53 of TDA9381, and outputs to the CRT board.
The V911, V921 and V931 are the R 、 、 G B drive transistors. The V912, V913, V922, V923, V932,
V933 are the auto low bright balance level output circuit, and generate the low bright level current into
the pin 50 of TDA9381.
The internal sound signal comes from the pin 44 of TDA9381, via the coupling capacitor C367
connects to the pin 3 and 5 of TDA9859. The TDA9859 is the audio effect processor, the AN7522N is
the driver. The TDA9859 includes bass, treble, balance, surround, effect shortcut options, additional
the audio input switch.