Sony UWP-V1, Service Manual

Page: 133 / 164

4-3
UWP Series
4-3
UTX-B2 UTX-B2
Circuit Description
UTX-B2
UTX-B2 consists of the following four blocks.
1.
Audio circuit and the peripheral circuit:
Ref No. 400 series and 500 series
2. PLL block and RF block:
Ref No. 300 series
3. CPU and the peripheral circuit:
Ref No. 600 series
4. Power supply block: Ref No. 10 through 50 series.
1. Audio circuit and the peripheral circuit
The audio input signal to the MIC INPUT connector
(CN401) is routed to the Mic/Line selector switch (S401),
and is sent to the audio attenuator (ATT) circuit (IC411) in
the unbalanced signal format. The ATT is set (0 to 21 dB
with 3 dB step) by the resistance value that is selected by
the analog switch (IC411). As the analog switch receives
the 3-bit ATT control signal (ATT0, 1, 2) from CPU
(IC601), it selects the resistance value accordingly. The
ATT control signal data is determined by the information
generated by the [
+ ] and [ _ ] switches (S671, S672) that
send the control data to the CPU (IC601).
The audio signal that is adjusted of its level by the ATT
circuit is buffered (Q421) and sent to the limiter circuit
(IC431). The limiter circuit monitors the audio input signal
level if the input signal level is excessive or not, and
controls the input signal level so as not to exceed the set
threshold level. The limiter output signal is passed through
a low-pass filter (IC431), is amplified (IC451) and sent to
the compressor circuit (IC471). The audio signal receives
the signal compression at the compressor circuit with the
compression ratio of 2 :1 (compressed to 1/2), and is sent
to the pre-emphasis circuit. Time constant of the pre-
emphasis circuit is 50
u
s. The audio signal is then mixed
with the tone signal (X511: 32.000 kHz), is passed through
the AF switch (IC521) and is sent to the RF circuit block
(VCO: CP101). The AF level detection circuit (IC451,
D451) is used to display the audio signal on the LCD
(ND651).
2. PLL block and RF block
The oscillator circuit is a PLL-frequency synthesizer type
oscillator. VCO (CP321) is a voltage-controlled oscillator
working as a transmission frequency oscillator and modu-
lator. The transmission frequency is controlled by the serial
data (PLL data) that is supplied from the CPU (IC601) to
the PLL IC (IC301) having the built-in pre-scalar.
The signal that is amplified by the RF amplifier (Q333,
Q351) is passed through a low-pass filter (L361 to L364,
C362 to C364) and is output from the antenna via the
isolator (CP361). At this time, the locked status of the PLL
can be detected by monitoring the LD terminal (pin-10) of
the PLL IC (IC301). The voltage control circuit (Q331,
Q332) has the function of switching ON/OFF the power
voltage to the RF circuit. The control signal to the voltage
control circuit is the RFM signal that is supplied from the
CPU (IC601). (Power is supplied to the RF circuit when
the RFM signal is “H”.)
3. CPU and the peripheral circuit
The CPU (IC601) is an 8-bit microprocessor operating on
the 8 MHz (X621) clock frequency.
The CPU (IC601) performs the functions of sending out
the PLL data, ATT (attenuation), setting the transmission
output power, AF muting, RF muting, LCD control and
others by accessing the EEPROM (IC661). The voltage
detection circuit (IC631) detected the power supply voltage
(
+
2.7 V) and uses it for resetting the CPU (IC601).
4. Power supply block
The DC-DC converter block (IC11, Q14, D11) generates
+
5 V (VCC1) from the battery voltage (3 V), and supplies
it to the audio block and RF block. The regulator circuit
(IC12) generates
+ 3.3 V (VCC2) from the + 5 V (VCC1),
and supplies it to the CPU block and PLL block.
The POWER switch circuit (POWER switch: S11, Q11 to
Q13) is the control circuit that turns ON/OFF the DC-DC
converter.