Kenwood TK-760G series Service Manual Download

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TK-760G/

(

)

/762G/

(

)

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Memory Circuit

The transceiver has a 2M-bit (256k x 8) flash ROM

(IC501) and an 8k-bit EEPROM (IC505). The flash ROM con-
tains firmware programs, data and user data which is pro-
grammed with the FPU. The EEPROM contains adjustment
data. The CPU (IC502) controls the flash ROM through an
external address bus and an external data bus. The CPU
controls the EEPROM through two serial data lines.

Control Circuit

The CPU carries out the following tasks:

1) Controls the shift register (IC9, IC510) AF MUTE, WIDE/

NARROW, T/R KEY outputs.

2) Adjusts the AF signal level of the audio processor (IC508)

and turns the filter select compounder on or off.

3) Controls the DTMF decoder (IC511).
4) Controls the LCD assembly display data.
5) Controls the PLL (IC3).
6) Controls the D/A converter (IC6) and adjusts the volume,

modulation and transmission power.

Fig. 9

Control circuit

Fig. 10

Memory circuit

CIRCUIT DESCRIPTION

IC6

D/A

converter

IC3

PLL

IC9

Shift

IC510

Shift

LCDCS

CNTCK

CNTDT

AFCLR
AFMSKE
AFSTB

IC508

Audio

processor

IC511

DTMF

DECO.

IC502

CPU

TX-RX UNIT

LCD ASSY

AFREG2

AFREG1

DTMDAT

DTMCLK

DTMSTD

DAST

PLST

PLDT

PLCK

SCL

SDA

IC502

CPU

ADDRESS BUS

DATA BUS

IC501

FLASH

ROM

IC505

EEPROM

Q506

Q508

Q504

Q505

MBL

LED1

LED0

IC510

Shift

D521

GRN

RED

D509~514

MBL

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Key Matrix Circuit

The TK-760G/762G front panel has function keys. Each

of them is connected to a cross point of a matrix of the KIN0
to KOUT2 ports of the microprocessor. The KOUT0 to
KOUT2 ports are always high, while the KIN0 to KIN2 ports
are always low.

The microprocessor monitors the status of the KIN0 to

KOUT2 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.

IC502

CPU

KIN0

KIN1

KIN2

KOUT0

KOUT1

KOUT2

D/A

GRP
DN

CH
DN

CH
UP

GRP
UP

VOL
DN

VOL
UP

Fig. 11

Display circuit

Fig. 12

Key matrix circuit

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Display Circuit

The CPU (IC502) controls the shift register (IC510) and

display LEDs. When the LED1 line goes high when the
transceiver is busy, Q508 turns on and the green LED on
D521 lights. In transmit mode, the LED0 line goes high,
Q504 turns on and the red light lights. Backlighting LEDs for
the key operation unit (D509~D514) and LCD are provided.

When the MBL line goes high, Q506 turns on, then Q505

turns on, and the key illumination LED lights. A voltage is
applied to the MBL line to turn on the LCD backlight.

■

Encode

The QT and DQT signals are output from TO of the CPU

(IC502) and summed with the external pin DI line by the
summing amplifier (IC2) and the resulting signal goes to the
D/A converter (IC6) of the TX-RX unit. The DTMF and 2-
TONE signals are output from DTMF of the CPU and goes to
the audio processor (IC508). The signal is summed with a
MIC signal by the audio processor (IC508), and the resulting
signal passes through an analog switch (IC509) and goes to
the TX-RX unit (MO).

The D/A converter (IC6) adjusts the MO level and the bal-

ance between the MO and TO levels. Part of a TO signal is
summed with MO and the resulting signal goes to the MD
pin of the VCO. This signal is applied to a varicap diode in
the VCO for direct FM modulation.

Fig. 13

Encode

VCXO

IC6

D/A

VCO

IC1

SUM

AMP

IC509

Analog

IC508