Vertex Standard VX-2500V Service Manual page 10

Circuit Description
The output of the VCO is amplified by the Q1020 and rout-
ed to the pin 5 of the PLL IC. Also the output of the VCO
is amplified by the Q1021 and routed first local/ Power
Module according to D1022 .
The PLL IC consists of a prescaler, fractional divider, ref-
erence divider and phase comparator and charge pump.
This PLL IC is fractional-N type synthesizer and performs
in the 40 or 50 kHz reference signal, which is eighth of the
channel step (5 or 6.25 kHz). The input signal from pin 5
and 8 of the PLL IC is divided down to the 20 kHz and
compared at phase comparator. The pulsed output signal
of the phase comparator is applied to the charge pump
and transformed into DC signal in the loop filter. The DC
signal is applied to the VCO and locked to keep the VCO
frequency constant.
PLL data is output from "DCS_E" (pin100), "CLOCK"
(pin2) and "PLL_E" (pin98) of the microprocessor Q2013 .
The data are input to PLL IC when the channel is changed
or when transmission is changed to reception and vice
versa. A PLL lock condition is always monitored by the
pin20 of the Q2013 . When the PLL is unlocked, the UL
goes low.
6. Miscellaneous Circuits
6-1 DCS/LTR Demodulator
DCS signals are demodulated on the PANEL-UNIT, It is
demodulated by Q2116 (AK2345), amplifier Q2015 , and
comparator Q2021 .
6-2 CTCSS encoder/decoder
The CTCSS code is generation and encoding by CTCSS
encoder/ decoder IC Q2016 (AK2345).
6-3 MPU
Operation is controlled by 8-bit MPU IC Q2013
(LC87F72C8A). The system clock uses a 3.6864MHz crys-
tal for a time base. IC Q2003 (S-80735SN) resets the MPU
when the power is on, and monitors the voltage of the
regulated 5V power supply line.
6-4 DCS/LTR Encorder
The DCS code is generation and encoding by MPU IC
Q2013 (LC87F72C8A). It is filtered by Q2021 (NJM2902V)
and adjusted the level by Q2014 (M62364FP).
6-5 Compandor
The Compandor is active when Pin90 of Q2013
(LC87F72C8A) is "High". When the Compandor is ac-
tive, MIC Audio is compressed, and detected audio is ex-
panded by Q2017 (LA8630M).
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7. Power Supply Circuits
7-1 All 13.8V
13.8V is always supplied to Power AMP Q1014
(RA30H4452M). Switched 13.8V is supplied to AF Power
AMP Q1509 (TDA2003H) and 9V Regulator Q1004
(MM1216EN) and Q1005 (2SB1201STP).
7-2 All 9V
9V regulated from 13.8V by Q1004 (MM1216EN) and
Q1005 (2SB1201STP).
7-3 VCO 9V
9V is filtered by Ripple Filter and is supplied to VCO Os-
cillator Q1013 (2SK508-K52), Q1015 (2SC5107-O), and
VCO BUFFER AMP Q1015 (2SC5107-O).
7-4 5V (RF-UNIT)
5V in RF-UNIT is regulated by REGULATOR IC Q1024
(NJM78L05UA). 5V is supplied to PLL IC Q1023
(SA7025DK), FM IC Q1028 (TA31136FN), and Reference
Oscillator Q1027 (23C4116GR).
7-5 TX 9V
TX 9V is active on transmit. TX 9V is supplied to ANT SW
D1005 , D1007 (UM9957F) and TX DRIVER Q1022
(2SC5415E), Q1025 (2SC5107-O).
7-6 RX 9V
RX 9V is active on receive. RX 9V is supplied to RX RF
AMP Q1026 (3SK228) and MIXER Q1011 (2SC4227-R34).
7-7 5V (RF-UNIT)
9V from RF-UNIT is regulated to 5V by REGULATOR IC
Q2006 (NJM78L05UA) in PANEL-UNIT.