5
Circuit Description
VR-120D separates into two substrate blocks. It is
RF unit and CNTL
•
AF unit.
ATT, ANT band path filter, bar ANT for AM,
RFAMP, 1st
•
2ndMIX, 2ndIF-AMP, 3rdIF-DETIC,
PLL, 1st
•
2nd-VCO, AMDET circuit are had by the
RF unit. Also, the CNTL
•
AF unit has a CPU, LCD,
a power, AUDIO circuit, EEPROM.
RF Unit
The signal which entered from ANT is stored in the
band path filter below the entering to the ATT
circuit.
It is amplified by RF-AMP Q216, Q217 which is
common after the band path filter passage.
The amplified RF signal entry to 1st-MIX Q218
(µPC2757T) with the 1st local signal, it makes a 1st
IF signal.
The 1st local oscillator is VCO Q241 (2SC5006). and
oscillated signal is amplified in the buffering in
Q240, Q239 (2SC5006).
The 1st-IF signal of 248.45MHz which passed the
SAW filter of F202 are input to 2nd-MIX Q219
(2SC5006), it mix with the 2nd local signal of
263.45MHz, and makes a 2nd-IF signal.
Amplifying the 2nd-IF in Q220 2SC4915, and It
detects and it gets a speech signal by IF IC of Q221
(TA31136FN).
3rd-IF is 450kHz. The AM detection is Q231
(UMX2N), it amplifies 3rd-IF signal and Q232
(RB520S-30) detects AM.
2nd-VCO is oscillated by Q229, and it is amplified
by Q228.
PLL IC is Q235 (MB15F02PFV). It forms 1st and
2nd PLL circuit.
The standard crystal oscillation circuit is Q234
(2SC4617), it oscillates 14.55 MHz crystal.
The loop filter for 1st local is Q236 (2SK1580), its
active type, and the loop filter for 2nd local is passive
type by CR.
CNTL•AF unit
The detected signal from the RF substrate, which is
amplified by Q130 (UMX2N), and volume
controlled signal amplified by Q123 (TA31056F),
and it outputs a sound from the speaker.
The DC input of 3V, which boosts the voltage to
3.5V by the DC-DC converter Q116
(XC6371A351PR). It is stabilized to 3.2 V by Q118
(S-81332HG-KC).
The main microprocessor is Q101 (HD643837S).
EEPROM is Q115 (AT24C64N-10SI1.8).
The reset IC is Q112 (RN5VL20AA).
The 10V boost circuit for RF VCO, which boosts
and detects by Q119, Q120, Q121 (RB706F).
Q122 (2SC4617R) is a ripple filter.
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