Af Signal System; Serial Control; Narrow/ Wide Switching Circuit; Beep Circuit And Mute Circuit - Kenwood TM-V71A Service Manual

TM-V71A/V71E

5-3. Serial Control

The MPU (IC918) controls the panel section (Display unit
X54-359) through synchronous serial communications.
MPU
IC918
Fig. 9 Structure of non-synchronized serial
communication

5-4. Narrow/ Wide Switching Circuit

On band A, the receiver bandwidth can be switched
between narrow and wide by selecting IF ceramic filters
CF487 (Narrow) and CF486 (Wide) with a switching circuit
(Q486, Q487, D486, D487).
On band B, the receiver bandwidth can also be switched
between narrow and wide by selecting IF ceramic filter
CF547 (Narrow) and CF546 (Wide) with a switching circuit
(Q546, Q548, D546, D547).
The transmitter deviation can be switched between
narrow and wide by setting the electronic variable resistor
(IC804) on the deviation adjustment point. It is controlled
from the MPU (IC918).
D486
D546
Fig. 10 Narrow/ Wide switching circuit
J801
(SP1)
J802
(SP2)
8
CIRCUIT DESCRIPTION
PANEL
X54-359
IC486
FM IC
CF WIDE
CF486
D487
CF NARROW
CF487
IC546
FM IC
CF WIDE
CF546
D547
CF NARROW
CF547
IC801
AF AMP
ATT
Q816 Q804 Q803
Fig. 11 Beep circuit and mute circuit

6. AF Signal System

6-1. Beep Circuit and Mute Circuit

A beep sound is generated by the MPU (IC918) and goes
to cross point switch (IC806). This signal is switched by
the cross point switch and is input to the electronic volume
(IC804). While the beep signal is output from the MPU,
audio signals for each band are muted by the cross point
switch with the serial data from the MPU (IC918). The beep
signal that has had its level adjusted by an electronic volume
is input to AF amplifi er (IC801).
6-2. Speaker Switching Circuit
There are two speaker jacks, J801 (SP1) and J802 (SP2).
The AF signals can be output in various combinations
matching the internal speakers. When an external speaker is
not connected to J802 (SP2), the J802 signal is added to the
AF amplifi er input of SP1 via the ATT circuit, and is output
through J801 (SP1). When an external speaker is connected
to J802 (SP2), it is output separately from a speaker for A /
B band. Crossing point switch connection can be switched
by switching the menu between MODE 1 and 2, and the
connection of SP1 and SP2.
The AF signal output combinations are shown in the
table below.
Speaker
Mode
None
SP1 only
MODE 1
SP2 only
SP1, SP2
None
SP1 only
MODE 2
SP2 only
SP1, SP2
Table 1 AF signal output combinations
IC804
E VR DE-EMPHASIS A
Q806 Q810
IC806
Cross
Point
Q807 Q811
SW
DE-EMPHASIS B
BEEP
IC805
DTMF
IC918
MPU
IC805
MUTE1
MUTE2
CTCSS Filter AMP
Band Output
Internal External
Setup
Speaker SP1
A, B –
x A, B
A –
x A
A, B –
x A, B
B –
x B
IC486
FM IC (A)
IC666
Multi
SW
IC546
FM IC (B)
1/2
1/2
External
SP2
–
–
B
B
–
–
A
A