TH-D72A/D72E
9
DC
SW
DC
SW
DC
SW
DC
SW
DC
SW
DC
SW
DC
SW
DC
SW
DC
SW
DC
SW
DC
SW
DC
SW
DC
SW
DC
SW
DC
SW
Regulator
3.3V
33M
IC715
V
detector
AFB
Main
MCU
TH
IC713
Regulator
4.5V
DC-DC
controller
DC-DC
converter
IC645
Regulator
3.3V
33C
IC718
Regulator
4.7V
Sub
MCU
Regulator
5.3V
Regulator
3.3V
Comp.
8.4V
47C
45RVAM
33CA
IC719
Q652
IC611
IC642
+
–
BT_V
IC646
Regulator
1.5V
IC643
Q646
IC641
Q651
SAVE1
SAVE1
DC
SW
A_S
DC
SW
DC
SW
33CB
33RB
PLL_B
VP
PLL_A
VP
B_S
45RVAM_S
Q615
45RUB
DC
SW
45RUB_S
Q611
45RVB
DC
SW
45RVB_S
Q614
45RUA
DC
SW
45RUA_S
Q613
45RVA
DC
SW
45RVA_S
45C
Q612
Q656
DC
SW
Q650
DC
SW
DC
SW
DC
SW
Q649
Q645
Q642
DC_S
+B
Q658
DC-DC
reset
IC644
IC639
Q663
LAMP
B
C_S
INT
AFB
AFB_S
IC705
Q721
Q722
LAMP
IC737
DC_DET
TH703
D650
Q662
D646
Q643
CHG
Q648
PRE_CHG
Q653
Q657
Q654
33RB_S
Q616
IC512
IC514
Q655
Q659
+
–
Battery
Terminal
DC-IN
JACK
Figure 5 Power supply circuit
7. AF Signal System
7-1. Reception AF circuit
■
Demodulation signal circuit
The reception AF signal demodulated by each IF IC
(IC353, IC354) for Band A/B is independently input to E-vol-
ume (IC721). The volume balance in each Band is pre-set.
To assume the AF level from the SP to be about the same in
each mode of Wide/Narrow, the output level of E-volume is
adjusted to half at the Wide mode in Narrow mode.
The reception AF signal passes the de-emphasis circuit
(Q718, Q717, Q715) and AF MUTE switch (Q711), and en-
ters the AF VOL for the loudness control. In addition, it is
amplifi ed by the Final AF Amplifi er (IC734), and SP is driven
through the SP MUTE switch (Q703).
Moreover, power consumption is reduced by intercept-
ing the DC switch (Q709) according to the SAVE2 signal
from the Main MCU (IC703) in save mode.
■
Tone decode circuit
The reception AF signal when the CTCSS, DCS and
Weather-alert-function (K-type only) are used, amplifi es the
selected signal to the necessary level with the active fi lter
amplifi er (IC722) individually prepared for Band A/B, and pro-
cesses the decode with the Main MCU (IC737).
■
BEEP, DTMF circuit
The BEEP and DTMF signals generated from the Main
MCU (IC737) are input to the Final AF Amplifi er (IC734), and
drive the SP through the SP MUTE switches (Q702, Q703).
When the BEEP and DTMF signals are output, it is as-
sumed that MUTE-ON by the AF MUTE switch (Q711) con-
trolled with the Main MCU (IC737), and it is separated and
output with the reception AF signal.
■
Squelch circuit
The Main MCU (IC737) takes the noise element (SQA,
SQB) and signal strength (SMA, SMB) obtained from each IF
IC (IC353, IC354), and controls the AF MUTE switch (Q703).
CIRCUIT DESCRIPTION