Kenwood TK-8102H Service Manual page 14

TK-8102H
Display Circuit
The CPU (IC6) controls the display LEDs. When the trans-
ceiver is busy, the LEDG line goes high, Q4 turns on and the
green LED (D11) lights. In transmit mode, the LEDR line
goes high, Q8 turns on and the red LED (D12) lights. Backlit
LEDs (D1~D4) are provided.
When a function key (MON, PF, C1, C2, C3 or C4) is se-
lected, its respective line goes high (LED MON, LED PF,
LED C1, LED C2, LED C3 or LED C4), the switch connected
to that line turns on and the amber LED lights.
LEDMON
LEDPF
LEDC1
LEDC2
LEDC3
LEDC4
LEDG
LEDR
MICBL
Fig. 12 Display circuit
Key Matrix Circuit
The TK-8102H front panel has function keys. Each of
them is connected to a cross point of a matrix of the KMI1 to
KMO2 ports of the microprocessor. The KMO1 to KMO2
ports are always high, while the KMI1 to KMI4 ports are al-
ways low.
The microprocessor monitors the status of the KMI1 to
KMO2 ports. If the state of one of the ports changes, the
microprocessor assumes that the key at the matrix point
corresponding to that port has been pressed.
KMI1
KMI2
KMI3
IC6
KMI4
CPU
KMO2
KMO1
Fig. 13 Key matrix circuit
14
CIRCUIT DESCRIPTION
Q1
SW
D5
Q5
SW
D6
Q2
SW
D7
Q6
SW
D8
Q3
SW
D9
Q7
SW
D10
Q4
SW
D11
Q8
SW
D12
Q10 Q9
SW SW
D1~4
VOL
C1
UD
VOL
C2
DN
C3 PF
C4 MON
Encode
The QT and DQT signals are output from QT/DQT of the
CPU (IC6) and summed with the external pin DI line by the
summing amplifier (IC4) and the resulting signal goes to the
D/A converter (IC3). The DTMF signal is output from DTMF
of the CPU and goes to the D/A converter (IC3). The signal
is summed with a MIC signal by the summing amplifier
(IC4), and the resulting signal goes to the D/A converter
(IC3).
The D/A converter (IC3) adjusts the MO level and the bal-
ance between the MO and QT/DQT levels. Part of a QT/
DQT signal is summed with MO and the resulting signal
goes to the VCOMOD pin of the VCO. This signal is applied
to a varicap diode in the VCO for direct FM modulation.
QT/DQT
SUM
AMP
IC6
CPU
DTMF
IC3
SUM
D/A
AMP
Fig. 14 Encode
Decode
• QT/DQT/DTMF
The signal (DEO) passes through two low-pass filters of
IC11, goes to QTIN of the CPU (IC6) to decode QT, DQT.
The DTMF signal is decoded by a dedicated IC (IC9) and the
resulting signal is sent to the CPU (IC6) as serial data.
IC11(2/2)
LPF
QTIN
IC6
SD
CPU
IC9
STD
DTMF
ACK
DECO.
Fig. 15 Decode
D/A Converter
The D/A converter (IC3) is used to adjust MO modulation,
AF volume, TV voltage, FC reference voltage, and PC
POWER CONTROL voltage level.
Adjustment values are sent from the CPU as serial data.
The D/A converter has a resolution of 256 and the following
relationship is valid:
D/A output = (Vin – VDAref) / 256 x n + VDAref
Vin: Analog input
VDAref: D/A reference voltage
n: Serial data value from the microprocessor (CPU)
TCXO
IC4
MOD
X1 IC1
TCXO PLL
DI
IC3
VCO
IC4
D/A
VCO
MOD
HT
IC11(1/2)
LPF
DEO