Kenwood TM-D700A Service Manual page 16

TM-D700A/E
CIRCUIT DESCRIPTION
16
7-2. Reception signals
PR9Q is the 9600bps data communications reception output.
It outputs the FM detection circuit output (RD signals) through a
buffer amp (Q700). These signals are always output whether
the squelch is open or closed.
PR1 is the 1200bps data communications reception output.
It outputs the FM detection circuit output (RA signals) through a
buffer amp (Q701). Output is controlled with the cross point
switch (IC702) according to whether squelch is open or closed.
7-3. Squelch signal output circuit
The squeich circuits is input to the TNC to prevents conflicts
from occurring between simultaneous receive mode and
transmit mode traffic during packet communications. (only
during 1200bps) The signal is output from Pin 15 of 1C703 to
the data terminal. The logic is as shown in the Table below.
8-3. Display circuit
The TM-D700A/E display section is a 188x54-dot full-dot
matrix LCD controlled by two LCD. As shown is Figure 19, the
master IC (IC2) side is connected to 22 common dots and 88
segment dots and the slave IC (IC1) side is connected to 33
common dots and 100 segment dots. The LCD drive voltage is
obtained by raising the power supply voltage (5V) within the IC.
L: SQ CLOSE
H : SQ BUSY
SQC terminal output
CoM LCD
188 x 54 (dot) 33
COM
sar
SEG
LCD LCD
Driver Driver
Ic2 IC1
at
it
(J700 Pin 6)
8. Panel Section (LCD ASSY: B38-0829-05)
The panel section controls serial communications with the
main unit control section, the key input circuit, the display
circuit, and the dimmer circuit through the microprocessor
(IC4).
8-1. Serial communications circuit
A buffer amp is inserted in order to protect the
microprocessor ports.
8-2. Key, Volume input circuit
Circuits to operate the panel section keys are connected to
each microprocessor port. The PSW key is pulled up and the
other keys are pulled up with software within the
microprocessor. Rotary encoder operating circuits are
connected directly to the microprocessor. The control divides
the power supply voltage, reads the A/D port of the
microprocessor, and transfers that data to the main unit.
Microprocessor
IC4
X54-329
Fig.19 Display circuit
8-4. Dimmer circuit
The dimmer circuit switches the lamp brightness to one of
four levels or OFF. (See table) The current flowing to the LEDs
is varied by selecting resistors from R8 to R14.
Dimmer level DIM O DIM 1 DIM 2 DIM 3
1 H L L L
20 L H L L
3 L L H L
4 L L L H
OFF L L L L
Table9 Port logic
C4
Microprocessor
R13 ov LCD ASSY
DIM3 Q8 p
R14
AYA 8
fen]
DIM2 Q7
Ri2. a
t+
a
DIM1 + --
R9
Q4 Q5
R10
R8
DIMO
Q
Fig.20 Dimmer circuit