Sony MB-806A Service Manual page 69

WRU-806A Tuner Unit
WRU-806A is composed of RF-92 board and DP-305
board.
Board name Q'ty _ Reference No.
RF-92 1 100s to 700s
DP-305 1 800s
RF-92 board
This board consists of the RF block, audio block, CPU block
and the voltage regulator block. This board receives the RF
signal input from the antenna A and B and outputs the de-
modulated audio signal. The RF circuit is used superhetero-
dyne techniques.
The same RF block is used for both antenna "A" and anten-
na "B".
The RF block consists of RF amplifier circuit, 1st mixer cir-
cuit, 2nd mixer circuit, IF circuit, FM detector circuit, Ist
local circuit and 2nd local circuit.
The RF signal which is input from the antenna A and B are
passed through band pass filter, amplified by RF amplifier,
passed through band pass filter and input to 1st mixer cir-
cuit. The RF signal is mixed with the 1st local signal in the
Ist mixer circuit where the input signal is converted to the
1st IF signal (150.75 MHz).
The ist IF signal is mixed with the 2nd local signal at the
2nd mixer circuit where the 1st IF signal is converted to the
2nd IF signal (10.7 MHz).
The 2nd IF signal is detected by the FM detector IC which
outputs audio signal. The audio signal is sent to the audio
block. The 2nd IF signal is converted to the RSSI signal by
the IF amplifier and is output to the CPU. The Ist local sig-
nal is generated by the PLL circuit. The 2nd local signal is
generated by the crystal oscillator.
The audio block consists of the tone signal detector circuit,
noise signal detector circuit, diversity switching circuit,
muting circuit, de-emphasis circuit, expander circuit and au-
dio amplifier circuit.
The FM detector outputs (audio outputs AF(A) and (B)) of
the RF block are amplified by the AF amplifier (A) and AF
amplifier (B) and is sent to the diversity switching circuit.
The diversity switching is controlled by the DIV signal from
the CPU.
The audio output signal from the diversity switching circuit
is passed through the muting circuit, de-emphasis circuit,
low pass filter circuit and expander circuit then amplified by
the AF amplifier.
DP-305 board
The DP-305 board is composed of display block and opera-
tion control block.
The display block has the LCD which indicates the various
status of group and channels and the AF indicator LED, RF
indicator LED and BATT indicator LED.
The operation control block consists of GP (S801), CH
(S802), + (S803), and — (S804) switches which perform the
setting such as group setting and channel setting.
RF-92 BOARD
RF Block (A)
fr +150. 75MHz
1
i
'
2, OB
CP601
'
int
'
'
'
Buffer (A)
Diversity
to RF and
AF Block
BATT Det.
10204, D204
0102, 103
fet Mixer SAWF
2nd Mixer BPF (CF)
IF Amp BPF (CF)
IF Amp
O
1
'
| 10701 i
1
iy
'
' CN104 FL1014 0101 FLI02
Ant. INT vs)
"Jenson
LoD '
ND801 |
CPU La 1
ED LED |
'
y—o y—o
'
H ' 7 fi
| [ eP CH + - |
| eae eee
'
BPF (CF) Discriminator |
Tuner Unit Block Diagram
WRU-806A
MB-806A (CE)
WRU-806A'(CE, AU)