Kenwood TK-285, TK-285-N Service Manual

VHF FM TRANSCEIVER

TK-285/(N)

SERVICE MANUAL

B51-8530-00(S) 847

CONTENTS

Panel assy (A62-0535-04)

Knob (PTT etc) (K29-5157-03)

Helical antenna (T90-0733-05):K, E (T90-0734-05):(N)M

Knob (ENC) (K29-5232-03)

Knob (VOL) (K29-5231-03)

Badge (B43-1106-14)

Cabinet assy (A02-2055-53) (16 keys)

GENERAL ................................................................................. 2

SYSTEM SET-UP ..................................................................... 2

OPERATING FEATURES......................................................... 3

REALIGNMENT ........................................................................ 4

CIRCUIT DESCRIPTION .......................................................... 6

SEMICONDUCTOR DATA ..................................................... 11

DESCRIPTION OF COMPONENTS....................................... 13

PARTS LIST............................................................................ 14

EXPLODED VIEW .................................................................. 22

PACKING ................................................................................ 23

ADJUSTMENT........................................................................ 24

TERMINAL FUNCTION .......................................................... 32

PC BOARD VIEWS

DISPLAY UNIT (X54-3210-13) ............................................ 33

TX-RX UNIT (X57-619X-XX) ............................................... 39

SCHEMATIC DIAGRAM ......................................................... 45

BLOCK DIAGRAM .................................................................. 49

LEVEL DIAGRAM ................................................................... 51

OPTIONS ................................................................................ 52

SPECIFICATIONS ...............................................BACK COVER

Photo is K type

Packing (G53-0896-02) (16 keys)

CAUTION

When using an external power connector, please use

with maximum final module protection of 9V.

TK-285/(N)

GENERAL / SYSTEM SET-UP

INTRODUCTION

SCOPE OF THIS MANUAL

This manual is intended for use by experienced technicians familiar with similar types of commercial grade communications equipment. It contains all required service information for the equipment and is current as of the publication data. Changes which may occur after publication are covered by either Service Bulletins or Manual Revisions. These are issued as required.

ORDERING REPLACEMENT PARTS

When ordering replacement parts or equipment information, the full part identification number should be included. This applies to all parts : components, kits, or chassis. If the part number is not known, include the chassis or kit number of which it is a part, and a sufficient description of the required component for proper identification.

Unit

Model & destination

TK-285

(N)M X57-6190-21 240~270MHz

TX-RX unit Display unit Frequency range Remarks Charger Battery

K E

X57-6190-11

X54-3210-13 TX : 218~250MHz

RX : 217~250MHz

PERSONNEL SAFETY

The following precautions are recommended for personnel

safety:

●

DO NOT transmit until all RF connectors are verified secure and any open connectors are properly terminated.

●

SHUT OFF and DO NOT operate this equipment near electrical blasting caps or in an explosive atmosphere.

●

This equipment should be serviced by a qualified technician only.

SERVICE

This radio is designed for easy servicing. Refer to the schematic diagrams, printed circuit board views, and alignment procedures contained within.

IF1 : 44.85MHz

LOC : 44.395MHz

OP ✔

SYSTEM SET-UP

Are you using the speaker microphone?

Merchandise received

Choose the type of transceiver

Transceiver programming

Delivery

Frequency range (MHz) RF power Type

TX 218~250 RX 217~250

TX/RX 240~270 5.0W TK-285 (N)M

A personal computer (IBM PC or compatible), programming interface (KPG-36), and programming software (KPG-62D) are required for programming. (The frequency, conventional system features, TX power HI/LOW, and signalling data are programmed for the transceiver.)

YES

KMC-25

Speaker microphone

(Option)

5.0W TK-285 K,E

OPERATING FEATURES

TK-285/(N)

1. Operation Features

The TK-285 is a VHF FM Radio designed in both Trunking

Mode and Conventional Mode.

2. Transceiver Controls and Indicators

2-1. Physical Layout

eqw

!0 !1 !2 !3

2-2. Panel controls

The key on the top and front panel is momentary-type push buttons. The functions of these keys and knob are explained below.

1 Antenna connector

Connect the antenna here.

2 Rotary encoder 3 POWER switch/ VOLUME control

Turn clockwise to switch ON the transceiver. Rotate to adjust the volume. Turn conterclockwise fully to switch OFF the transceiver.

4 Auxiliary (orange) key 5 Battery pack release latch

Pull back on this latch to release the battery pack.

6 Call key 7 PTT (Push-To-Talk) switch 8 Clear key 9 Transmit/ Receive indicator 0 A key

- B key = 2 C key ~ D 3 key ! DTMF keypad @ Universal connector

Connect the (optional KMC-25) speaker/ microphone here. Otherwise, keep the supplied cover in place.

SpeakerMicrophone

2-3. Key functions

Trunking mode 2 Rotary encoder

Rotate this encoder to select your desired call address (voice calls) ot status (status calls).

4 Auxiliary (orange) key (default setting: None)

Press to activate its auxiliary function.

6 Call key

Press to call the displayed call address.

7 PTT (Push-To-Talk) switch

Press to transmit. Also press to initiate a call if “PTT to Initiate Call” has been programmed.

8 Clear key

Press to end the current call.

9 Transmit indicator

Lights red while transmitting.

0 A key (default setting: Status/ Stack)

Press to activate its auxiliary function.

- B key (default setting: Redial) Press to activate its auxiliary function.

= 2 C key (default setting: None)

Press to activate its auxiliary function. Also press to scroll left while viewing stack entries.

~ D 3 key (default setting: None)

Press to activate its auxiliary function. Also press to scroll right while viewing stack entries.

! DTMF keypad

Press to input a call address or dialing function.

Conventional mode 2 Rotary encoder

Rotate this encoder to select your desired channel.

6 Call key

Press to turn the monitor function ON in order to monitor your selected channel.

7 PTT (Push-To-Talk) switch

Press this switch, then speak into the microphone to call a station.

8 Clear key

Press to return to Trunking mode.

9 Transmit/ Receive indicator

Lights green while receiving a signal. Lights red while transmitting.

0 A key

Press to turn Scan ON (or OFF).

- B key

Press to add/delete channel(s) to/from Scan list.

~ D 3 key

Press to turn the display and keypad backlight ON. The backlight remains ON for 5 seconds.

TK-285/(N)

OPERATING FEATURES / REALIGNMENT

2-4. Display

123459678

SVC

MON

1 Sub display

displays the strength of received signals.

2 Programming indicator

P appears while in AUX A or Scrambler is being activated.

3 MON (Monitor) indicator

MON appears while you are monitoring a channel by pressing the Call key. (Conventional Mode only)

4 SVC (Service) indicator

SVC appears when a control channel is found. It flashes while the transceiver is searching for a control channel.

5 SCN (Scan) indicator

SCN appears while you are scanning. (Conventional Mode only)

6 LO indicator

This icon blinks while in battery warning, if “Always” or “Always W/beep” is selected in the battery warning settings.

7 Handset indicator

flashes when you activate call diversion.

8 MAIL indicator

appears while there is data in the stack. It flashes when

there is new data in the stack.

9 Alphanumeric display

displays call addresses, the call duration timer, data messages, and the current operating status of the transceiver.

SCN LO

REALIGNMENT

1. Modes

User mode

Panel test mode

Firmware programming mode

PC mode

Panel tuning mode

Data programming mode

PC test mode

PC tuning mode

Mode Function

User mode For normal use. Panel test mode Used by the dealer to check the

fundamental characteristics. Panel tuning mode Used by the dealer to tune the radio. PC mode Used for communication between the

radio and PC (IBM compatible). Data program- Used to read and write frequency data ming mode PC test mode Used to check the radio using the PC.

Firmware program- Used when changing the main ming mode program of the flash memory.

and other features to and from the radio.

This feature is included in the FPU.

See panel tuning.

2. How to Enter Each Mode

Mode Operation

User mode Power ON Panel test mode [B]+Power ON PC mode Received commands from PC Panel tuning mode [Panel test mode]+[A] Firmware programming mode

[A]+Power ON

3. Panel Test Mode

Setting method refer to ADJUSTMENT.

4. Panel Tuning Mode

Setting method refer to ADJUSTMENT.

5. PC Mode

5-1. Preface

The TK-285 transceiver is programmed by using a personal computer, programming interface (KPG-36) and programming software (KPG-62D).

The programming software can be used with an IBM PC or compatible. Figure 1 shows the setup of an IBM PC for programming.

5-2. Connection procedure

1. Connect the TK-285 to the personal computer with the

interface cable.

2. When the POWER switch on, user mode can be entered

immediately. When PC sends command the radio enter PC mode, and “PROGRAM” is displayed on the LCD. When data transmitting from transceiver, the red LED is blinking. When data receiving to transceiver, the green LED is blinking.

Notes:

• The data stored in the personal computer must match model

type, when it is written into the flash memory.

• Change the TK-285 to PC mode, then attach the interface

cable.

REALIGNMENT

TK-285/(N)

5-3. KPG-36 description

(PC programming interface cable: Option)

The KPG-36 is required to interface the TK-285 to the computer. It has a circuit in its D-subconnector (25-pin) case that converts the RS-232C logic level to the TTL level.

The KPG-36 connects the universal connector of the TK285 to the computers RS-232C serial port.

5-4. Programming software KPG-62D Description

The KPG-62D is the programming software for the transceiver supplied on three 3.5" floppy disks. This software runs under MS-Windows 95/98 on an IBM-PC or compatible machine.

The data can be input to or read from the trnsceiver and edited on the screen. The programmed or edited data can be printed out. It is also possible to tune the transceiver.

We recommend that install the KPG-62D for example to hard disk first then use it.

5-5. Programming with IBM PC

If data is transferred to the transceiver from an IBM PC with the KPG-62D, the destination data (basic radio information) for each set can be modified. Normally, it is not necessary to modify the destination data because their values are determined automatically when the frequency range (frequency type) is set.

The values should be modified only if necessary. Data can be programmed into the flash memory in RS-232C format via the universal connector.

KPG-62D instruction manual parts No. : B62-1354-XX

IBM-PC

KPG-36

KPG-62D

Fig. 1

6. Firmware Programming Mode

6-1. Preface

Flash memory is mounted on the TK-285. This allows the TK-285 to be upgraded when new features are released in the future. (For details on how to obtain the firmware, contact Customer Service.)

6-3. Programming

1. Start up the firmware programming software (Fpro.exe).

2. Set the communications speed (normally, 57600 bps) and communications port in the configuration item.

3. Set the firmware to be updated by File name item.

4. Turn the TK-285 power ON with the [A] switch held down. Hold the switch down until the display changes to "PROG 57600". When "PROG 57600" appears, release your finger from the switch.

Check the connection between the TK-285 and the personal computer, and make sure that the TK-285 Is in the Program mode.

6. Press write button in the window. A window opens on the display to indicate progress of writing. When the TK-285 starts to receive data. the [P] icon is blinking.

7. If writing ends successfully. the LED on the TK-285 lights and the checksum is displayed.

8. If you want to continue programming other TK-285 s, repeat steps 4 to 7.

Notes:

●

This mode cannot be entered if the Firmware Programming mode is set to Disable in the Programming software (KPG62D).

●

When programming the firmware, it is recommend to copy the data from the floppy disk to your hard disk before update the radio firmware. Directry copying from the floppy disk to the radio may not work because the access speed is too slow.

6-4. Function

1. If you press the [Call] switch (top of left side) while "PROG 57600" is displayed, the version is displayed. If you press the [Call] switch again while the version is displayed, "PROG 57600" is redisplayed.

2. If you press the [Clear] switch (bottom of left side) while "PROG 57600" is displayed, the display changes to "PROG 19200" to indicate that the write speed is low speed (19200 bps). If you press the [Clear] switch again while "PROG 19200" is displayed, the display changes to "PROG 38400", and the write speed becomes the middle-speed mode (38400 bps). If you press the [Clear] switch again while "PROG 38400" is displayed, the display returns to "PROG 57600".

3. If you press the [Clear] switch while the version is displayed, the checksum is displayed. If you press the [Clear] switch again while the checksum is displayed, the version is redisplayed.

Note:

Normally, write in the high-speed mode.

6-2. Connection procedure

Connect the TK-285 to the personal computer (IBM PC or compatible) with the interface cable (KPG-36). (Connection is the same as in the PC Mode.)

TK-285/(N)

CIRCUIT DESCRIPTION

1. Overview

This transceiver is VHF/FM portable transceiver designed to operate in the frequency range of 217 to 250MHz (K, E), 240 to 270MHz ((N)M).

2. Circuit Configuration by Frequency

The receiver is a double-conversion superheterodyne with a first intermediate frequency (IF) of 44.85MHz and a second IF of 455kHz. Incoming signals from the antenna are mixed with the local signal from the PLL to produce the first IF of

44.85MHz.

This is then mixed with the 44.395MHz second local oscillator output to produce the 455kHz second IF. This is detected to give the demodulated signal.

The transmit signal frequency is generated by the PLL VCO, and modulated by the signal from the microphone. It is then amplified and sent to the antenna.

RX : 217~250MHz (K,E)

RX : 240~270MHz ((N)M)

TX : 218~250MHz (K,E)

TX : 240~270MHz ((N)M)

ANT

1st MIX

AMP

261.85~294.85MHz (K,E)

284.85~314.85MHz ((N)M)

218~250MHz ( 240~270MHz (

ANT

AMP

Fig. 1 Frequency configuration

MCF

44.85MHz

K,E (N)M

)

455kHz

FM IF

SYSTEM

PLL

VCO

AMP

44.395MHz

MIC

AMP

MIC

3. Receiver System

3-1. RF unit

An incoming RF signal from the antenna terminal is passed through the antenna switch (D12, D14, D22 and D401 are off) and then the bandpass filter (L403,404,405,406). The bandpass filter is adjusted by a variable capacitor. The input voltage to the variable capacitor is regulated by the voltage output from the D/A converter (IC8). The signal is amplified by RF amplifier (Q24), and passed through the bandpass filter (L31,33) and band-eliminate filter (L27,29) to remove the spurious signal again. The resulting signal is applied to the first mixer (IC18), where it is mixed with the first local oscillator signal output from the frequency synthesizer to produce the first IF (44.85MHz). The 1st mixer uses the GaAs IC.

3-2. IF unit

The first IF signal is passed through a crystal filter (XF1) to remove a adjacent channel signal. The filtered first IF signal is amplified by the first IF amplifier (Q12) and then applied to the lF system IC (IC12). The IF system IC provides a second mixer, second local oscillator, limiting amplifier, quadrature detector and RSSI (Received Signal Strength Indicator). The second mixer mixes the first IF signal with the 44.395MHz of second local oscillator output (crystal unit X2) and produces the second IF signal of 455kHz.

The second IF signal is passed through the ceramic filter (CF2) to more remove the adjacent channel signal. The filtered second IF signal is amplified by the limiting amplifier and demodulated by the quadrature detector with ceramic discriminator (CD1). The demodulated signal is routed to the audio circuit.

ANT

BPF

Q24

AMP

L31,33

BPF

L27,29

DE-

EMP

BEF

IC18

1st MIX

1st Local

OSC (PLL)

EXP

XF1

MCF

MUTE

Q12

1st IF

MIX, DET, IF

2nd local

OSC

IC7 (2/2) AF AMP

IC12

VOL

IC8

CF2

Q15

DMDM

Q310

SSW

IC4 (2/2) AF AMP

VC1

VC2

IC300

AF PA

INT.

EXT.

L40,42,

IC13

HPF LPF HPF BEF

L403,404,

D12,14,

D15,401

405,406

ANT

Fig. 2 Receiver section

CIRCUIT DESCRIPTION

DET

BPF

AMP

DET

RSSI

NOISE

AMP

IC19 CPU

IF AMP

IC12 : FM IF IC

Q4 D4

SQ close

SQ open

Preset Value

ANT input level

SQ voltage

ANT input level

RSSI voltage

S-Meter level

TK-285/(N)

3-3. Audio amplifier circuit

The demodulated signal from IC12 goes through the mute switch (Q15) and is amplified by IC4 (2/2), high-pass filtered, low-pass filtered, high-pass filtered, band-eliminate filtered, and de-emphasized by IC13.

The signal then goes through an AF amplifier IC7 (2/2), an electronic volume control (IC8), and an AF switch (Q310 is on), and is routed to audio power amplifier (IC300), where it is amplified and output to the internal speaker.

The audio mute signal (AM) from the shift register becomes Low in the standby and Q304, Q305 which are power supply circuit for IC300 turn off. Also, IC13 is set to the power down mode according to data from microprocessor, and the AF signal is muted. When the audio is output, AM becomes High to turn Q304, Q305 ON, and voltage is supplied to power terminal VP of IC300. Also, IC13 is canceled out of the power down mode.

The speaker is switched by the logic of speaker switching terminal SSW on the universal connector. When SP-MIC is not attached, the logic of SSW becomes High and SW (Q310) is turned ON, and the AF signal is input to both amplifiers of IC300.

When SP-MIC is attached, SSW is connected to GND at inside of SP-MIC. For this reason, Q310 is turned OFF, and the AF signal is input only to amplifier for EXT SP of IC300.

Change of INT/EXT SP refer to Fig. 3.

3-4. Squelch circuit

The output from IC12 enters FM IC again, then passed through a band-pass filter. The noise component output from IC12 is amplified by Q4 and rectified by D4 to produce a DC voltage corresponding to the noise level. The DC voltage is sent to the analog port of the CPU (IC19). And IC12 outputs a DC voltage (RSSI) corresponding to the input of the IF amplifier. The CPU reads the RSSI signal via pin 93.

IC19 determines whether to output sounds from the speaker by comparing the input voltage of pin 91 and pin 93 with the preset value.

Fig. 4 Squelch circuit

AM SSW VC1 VC2 SP

H H H L INT H L L H EXT

L H L L MUTE L L L L MUTE

SSW

Q301

Q304

Q308

Q305

VC1

VC2

Fig. 3 Audio amplifier circuit

VP 5

IC300

INT.SP

EXT.SP

Fig. 5 Squelch and RSSI voltage vs ANT input level

4. Transmitter System

4-1. Microphone amplifier

The signal from the internal microphone goes through the mute switch (Q300).

When the SP-MIC is not attached, the microphone switching terminal (MSW) on the universal connector becomes High, and mute switch (Q300) is turned ON. When the SP-MIC is attached, MSW is connected to GND at inside of SP-MIC. For this reason, Q300 is turned OFF, the internal microphone is muted, and only the input of the external microphone is supplied to the microphone amplifier of the TX-RX unit.

The signal from microphone passes through the limitter circuit in D8, and Mic mute switch (Q17 is off in TX) and through the low-pass filter (IC25:1/2), the high-pass filter, the ALC circuit, the low-pass filter, the high-pass filter, and preemphasis/IDC circuit in IC13. When encoding DTMF, mute switch (Q13) is turned OFF for muting the microphone input signal.

The signal passes through the D/A converter (IC8) for the maximum deviation adjustment, and enters the summing amplifier consisting of IC7 (1/2), and is mixed with the low speed data from the CPU (IC19) and 9600bps DATA from Optional Board Terminal.

TK-285/(N)

CIRCUIT DESCRIPTION

The output signal from the summing amplifier passes through the D/A converter (IC8) again and goes to the VCO modulation input.

The other output signal from the summing amplifier passes through the D/A converter (IC8) again for the BAL adjustment, and the buffer amplifier (IC1 : 2/2), and goes to the VCXO modulation input.

MUTE

EXT.

MIC

Q300 D8

MIC

Q301

MIC

MUTE

PTTMSW

Q17

LIMIT

IC25(1/2)

LPF

Q13

IC13

HPF

IC8 D/A

ALC

LSD DI9

IC7 (1/2)

SUM AMP

COMP

DTMF

18 19

LPF HPF IDC

IC8 D/A

IC8 IC1 D/A

PRE

EMP

VCO

BUFF AMP

Fig. 6 Microphone amplifier

4-2. Drive and Final amplifier

The signal from the T/R switch (D9 is on) is amplified by drive amplifier (Q20) to 30mW.

The output of the drive amplifier is amplified by the RF power amplifier (IC100) to 5.0W (1W when the power is low). The RF power amplifier consists of two stages MOS FET transistor. The output of the RF power amplifier is then passed through the harmonic filter (LPF) and antenna switch (D12 and D401 is on) and applied to the antenna terminal.

ANT

From

T/R SW

(D9)

REF

VOL

(IC8)

R244

R246

R248

Q20 IC100

DRIVE

AMP

IC23 (1/2)

POWER AMP

VDD

IC23 (2/2)

VGG

D12,D401

ANT

LPF

Fig. 7 Drive and final amplifier and APC circuit

4-3. APC circuit

The APC circuit always monitors the current flowing through the RF power amplifier (IC100) and keeps a constant current. The voltage drop at R244, R246 and R248 is caused by the current flowing through the RF power amplifier and this voltage is applied to the differential amplifier (IC23 1/2).

IC23(2/2) compares the output voltage of IC23(1/2) with the reference voltage from IC8, and the output of IC23(2/2) controls the VGG of the RF power amplifier to make the both voltages to same voltage.

The change of power high/low is carried out by the change of the reference voltage. Q22,23 and 25 are turned on in transmit and the APC circuit is active.

VCXO

5. Frequency Synthesizer Unit

5-1. Frequency synthesizer

The frequency synthesizer consists of the VCXO (X1), VCO

(A1), PLL IC(IC14) and buffer amplifiers.

The VCXO generates 16.8MHz. The frequency stability is

1.5ppm within the temperature range of -30 to +60˚C. The frequency tuning and modulation of the VCXO are done to apply a voltage to pin 1 of the VCXO. The output of the VCXO is applied to pin 8 of the PLL IC.

The TK-285’s VCO consists of 2VCO and covers a dual

range of the 261.85~294.85MHz (K,E), 284.85~314.85MHz ((N)M) and the 218~250MHz (K,E), 240~270MHz ((N)M).

The VCO generates 261.85~294.85MHz (K,E),

284.85~314.85MHz ((N)M) for providing to the first local signal in receive. In TX, the pin 3 of the VCO goes low and the VCO generates 218~250MHz (K,E), 240~270MHz ((N)M).

The output of the VCO is amplified by the buffer amplifier (Q16) and routed to the pin 5 of the PLL IC. Also the output of the VCO is amplified by the buffer amplifier (Q18) and routed to the next stage according to T/R switch (D9, D23).

The PLL IC consists of a prescaler, fractional divider, reference divider, phase comparator, charge pump. This PLL IC is fractional-N type synthesizer and performs in the 40, 50 or 60kHz reference signal which is eighth of the channel step (6.25kHz). The input signal from the pins 5 and 8 of the PLL IC is divided down to the 50kHz and compared at phase comparator. The pulsed output signal of the phase comparator is applied to the charge pump and transformed into DC signal in the loop filter (LPF). The DC signal is applied to the pin 1 of the VCO and locked to keep the VCO frequency constant.

PLL data is output from DT (pin 75). CP (pin 19) and EP (pin 47) of the microprocessor (IC19). The data are input to the PLL IC when the channel is changed or when transmission is changed to reception and vice versa.

T/R

(TX : Low)

LPF

CPU

IC19

BUFF

VCXO

Q18

BUFF

Q16

To mixer

T/R

VCO

DT,CP,EP

IC14

PLL

Fig. 8 PLL block diagram

IC1

D23

BAL

To drive amp

CIRCUIT DESCRIPTION

IC19 CPU

Q5 Q1 Q0 Q2 Q6 Q7 Q3

Vss

Vdd RES CLK

CL CA Q9 Q4 Q8

KI1

KI2

KRST

IC301

16 keys

TK-285/(N)

6. Control Circuit

The control circuit consists of microprocessor (IC19) and its peripheral circuits. It controls the TX-RX unit and transfers data to and from the display unit. IC19 mainly performs the following;

1) Switching between transmission and reception by PTT signal input.

2) Reading system, group, frequency, and program data from the memory circuit.

3) Sending frequency program data to the PLL.

4) Controlling squelch on/off by the DC voltage from the squelch circuit.

5) Controlling the audio mute circuit by decode data input.

6) Transmitting tone and encode data.

6-1. Memory circuit

Memory circuit consists of the CPU (IC19) and a flash

memory (IC17).

A flash memory has a capacity of 2M bits and contains the transceiver control program for the CPU and the data for operating features.

This program can be easily downloaded from an external device.

6-2. Low battery warning

The battery voltage is monitored by the microprocessor (IC19). When the battery voltage falls below the voltage set by the Low Battery Warning adjustment, the red LED flashes to notify the operator that it is time to replace the battery. If the battery voltage falls even more (approx. 5.8V), a beep sounds and transmission is stopped.

Low battery warning

The red LED flashes during transmission

The red LED flashes and continuous beep sounds while PTT pressed

Battery condition

The battery voltage is low but the transceiver is still usable.

The battery voltage is low and the transceiver is not usable to make calls.

6-3. Key input

If the clock is supplied to CLK terminal when the RES terminal (CPU pin 78) of the decade counter (IC301) is set to Low, Q0 to Q7 become High sequentially. Normally, KI1 and KI2 are Low (pulled down). When any key is pressed. KI1 or KI2 become High. The CPU detects which key is pressed, according to the voltage of KI1 and Kl2 and clock timing.

●

Flash Memory

Note : The flash memory stores the data containing the FPU

(KPG-62D) program, Security Number (MPT Serial Number) and firmware program (User mode, Test mode, Tuning mode, etc.). This data must be reinstalled when replacing the flash memory.

●

EEPROM

Note : The EEPROM stores tuning data (Deviation, Squelch,

etc.) Realign the transceiver after replacing the EEPROM.

IC19

CPU

FLASH

IC17

IC20

EEPROM

Fig. 9 Memory circuit

RESET

CLOCK

INHIBIT

CARRY

OUT

Fig. 10 Key input

Fig. 11 Decade counter timing chart

TK-285/(N)

Display unit

5RC

5TC

5CNS

IC6

IC9

IC5

RF power amp (IC100)

ON/OFF

VOL

CIRCUIT DESCRIPTION

7. Signalling Circuit

7-1. Encode

●

Low-speed data (QT,DQT)

Low-speed data is output from pin 1 of the CPU. The signal passes through a low-pass CR filter, and goes to the summing amplifier (IC7 1/2). The signal is mixed with the audio signal and goes to the VCO (A1) and VCXO (X1) modulation input after passing through the D/A converter (IC8) for BAL adjustment.

●

High-speed data (DTMF)

High-speed data (HSD) is output from pin 2 of the CPU. The signal passes through a low-pass filter consisting of IC10, and provides a TX HSD tone and a RX HSD tone. TX HSD deviation making an adjustment by microprocessor is passed through the D/A convertor (IC8) and then applied to the audio processor (IC13).

The signal is mixed with the audio signal and goes to the VCO and VCXO. The RX HSD tone is passed a summing amplifier (IC7 2/2). The D/A converter (IC8) for audio control, audio power amplifier and then to the speaker.

●

FFSK

ESN utilizes 1200bps FFSK signal. FFSK signal is output from pin 6 of IC13. The signal passes through the D/A converter (IC8) for the FFSK deviation adjustment. and is routed to the VCO. When encoding FFSK, the microphone input signal is muted.

RX Audio

LSD

OUT

IC19 CPU

R166

HSD OUT

C176

R162

C170

SUM

IC10

LPF

R136

IC7 (2/2)

SUM

IC7(1/2)

D/A (ADJ)

IC8

AF AMP

SUM

MIC IN

IC1

BUFF AMP

IC13

VCO

VCXO

7-2. Decode

●

Low-speed data (QT,DQT)

The demodulated signal from the IF IC (IC12) is amplified by IC4 (2/2) and passes through a low-pass filter (IC11) to remove audio components. The signal is input to pin 95 of the CPU.

The CPU digitizes this signal, performs processing such as DC restoration, and decodes the signal.

●

FFSK

The FFSK input signal from the IF IC is amplified by IC4 (1/ 2) and goes to pin 5 of IC13. The signal is demodulated by FFSK demodulator in IC13. The demodulated data goes to the CPU for processing.

IC13

IC4

AMP

AF IC

IC11

LPF

LSD IN

IC19 CPU

AF RDT

Fig. 13 Decode

8. Power Supply Circuit

Battery +B is supplied via a 3A fuse from the battery terminal connected to the TX-RX unit. After passing through the power switch, power supply (SB) is applied to the three AVRs. IC5 supplies 5V (5M) to the control circuit, and IC9 supplies 5V (5C) to common circuits. IC6 supplies to the TX circuit, the RX circuit and common circuits of needless save mode. During transmission, 5TC becomes Low and Q3 is turned ON to supply 5V (5T) to the TX circuit. During reception, 5RC becomes Low and Q2 is turned ON to supply 5V (5R) to the RX Circuit.

Fig. 12 Encode

Fig. 14 Power supply circuit

TK-285/(N)

CIRCUIT DESCRIPTION / SEMICONDUCTOR DATA

9. Optional Board Terminal

Terminals for mounting the option board are provided at the bottom edge of the TX-RX unit. The table below shows the correspondence between the board and terminals. R37, R69, R249, R258, R259, R304, R305 may have to be removed depending on the type of option board being used.

Name Function

SB Battery (7.5V) GND Ground TXD Serial data RXD Serial data SQ Busy: high LOK Link acquired : low (TX mode) DI/ANI Modulation (ANI) input DEO Detect output TXAI/MUTE TXAO Modulation input to board RXAI Received signal input to board RXAO Received signal output from board D1 Binary 1 D2 Binary 2 OPT Scramble, Emergency:low PTTIN PTT switch signal input to board (TX:low) 5CNS Battery (5V) DI9 9600 bps data input RXEMAO Received signal output from board (after de-

RXEMAI Received signal input to board (after de-

PTTOUT PTT switch signal output from board (TX:low) MONI Busy:low LAMP Busy:low AAC Audio Amp Control signal output from board

Audio Beep Beep signal output from board. AUX TXD Serial data AUX RXD Serial data/Option switch port. /EXT SW

Modulation output from board or mic mute: low

emphasis)

(Busy:high)

Table 1 Terminal name and function

SEMICONDUCTOR DATA Microprocesser : 30620M8-394GP

(TX-RX UNIT : IC19)

■ Pin function

Pin Port No. Name

1 LSDOUT O Low speed data output. 2

HSDOUT 3 HSDIN I High speed data input. 4

DTMSTD 5 SELF I Self programming mode input. 6 BYTE I +5V. 7 CNVSS I GND. 8 SFTOE O Shift register output enable. 9 LCDCS O LCD driver chip select output.

10 RESET I Microcomputer reset input. 11 XOUT - 9.8304MHz (System clock). 12 VSS - GND. 13 XIN - 9.8304MHz (System clock). 14 VCC - +5V 15 AUX I AUX switch input. 16 AFTRD I FFSK modulation data output timing pulse

17 AFRTM I FFSK demodulation data input timing pulse

18 EN2 I Encoder pulse input 2. 19 PLLCLK O PLL IC clock output. 20 BEEP O Beep data output. 21 AFRDT I FFSK demodulation data input. 22 AFREG1 O AF IC register switching data output 1. 23 AFREG2 O AF IC register switching data output 2. 24 EEPDAT O EEPROM data output. 25 DACSTB O D/A converter IC data strobe output. 26 AFCLR O FFSK flame reset output. 27 SAVE O Battery save output. 28 LAMP I LAMP switch input. 29 AUXTXD O External Serial interface output. 30 AUXRXD I External Serial interface input. 31 PLLUL I PLL unlock detect input. 32

AFFFSKE

33 TXD O Serial interface output (ex. PC). 34 RXD I Serial interface input (ex. PC). 35 AFDAT O FFSK data output. 36 PTT I PTT switch input. 37 RDY - Not used. 38 ALE - Not used. 39 HOLD - Not used. 40 HLDA - Not used. 41 BLCK - Not used. 42 RD - Flash memory RD bus. 43 BHE - Not used. 44 WR - Flash memory WR bus. 45 DTMCLK O DTMF decode IC clock output. 46 CNTCLK O Common clock output. 47 PLLSTB O PLL IC data strobe output. 48 CS0 O Flash memory chip enable.

I/O Function

O High speed data output.

I DTMF decode IC data detect input.

input.

FFSK modulation enable (Enable active “H”).

TK-285/(N)

SEMICONDUCTOR DATA

Pin Port

No. Name

49 A19 - Not used.

50~59

A9~A18 - Flash memory address bus. 60 VCC - +5V 61 A8 - Flash memory address bus. 62 VSS - GND.

63~70

A0~A7 - Flash memory address bus. 71 MONI I Monitor switch input. 72 EN4 I Encoder pulse input 4. 73 EN3 I Encoder pulse input 3. 74 EN1 I Encoder pulse input 1. 75 MINDAT O Common data output. 76 KEY2 I Key scan input 2. 77 KEY1 I Key scan input 1. 78 RESET O Key scan IC reset output..

79~86

D0~D7 - Flash memory data bus. 87

DTMDAT 88 PF I PF switch input. 89 VOL I Volume level input. 90 BATT I Battery voltage input. 91 ANLSQL I Squelch level input. 92 TEMP I Thermistor input. 93 RSSI I Received signal strength indicator input

94 AVSS - GND. 95 LSDIN I Low speed data input. 96 VREF - +5V 97 AVCC - +5V 98

SFTSTB1 99 W/N O Wide/Narrow switching output.

100 AFSTB O AF IC data strobe output.

I/O Function

I DTMF decode IC data input.

(RSSI).

O Shift register data strobe output.

PLL System : SA7025DK (TX-RX Unit : IC14)

■ Block diagram

■ Pin description

Pin No.

Symbol Description

1 CLOCK Serial clock input. 2 DATA Serial data input. 3 STROBE Serial strobe input. 4 Vss Digital ground. 5RFIN Prescaler positive input. 6 RFIN Prescaler negative input. 7 VccP Prescaler positive Supply voltage. This pin supplies

power to the prescaler and RF input buffer. 8 REFIN Reference divider input. 9 RA Auxiliary current setting; resistor to VSSA.

10 AUXIN AuxIliary divider input. 11 PHA Auxiliary phase detector output. 12 VSSA analog ground. 13 PHI Integral phase detector output. 14 PHP Proportional phase detector output. 15 VDDA Analog supply voltage. This pin supplies power

to the charge pumps, Auxiliary prescaler.

Auxiliary and Reference buffers.

16 RN Main current setting; resistor to VSSA. 17 RF Fractional compensation current setting;

resistor to VSSA.

18 LOCK Lock detector output. 19 TEST Test pin; connect to VDD. 20 VDD Digital supply voltage. This pin supplies power

to the CMOS digital part of the device.

DESCRIPTION OF COMPONENTS

DISPLAY UNIT (X54-3210-13)

Ref. No.

IC300 IC Audio power amplifier IC301 IC Counter /Key scan

Q300 FET DC switch / INT MIC on/off Q301 FET DC switch Q302 Transistor DC switch / LED (Red) driver Q303 Transistor DC switch / LED (Green) driver Q304 Transistor DC switch Q305 Transistor Current driver / Audio amp AVR Q306 Transistor DC switch Q307 Transistor Current driver Q308 FET DC switch / SP INT/EXT Q309 Transistor Temperature compensation Q310 FET Mute switch

D300 Zener diode Surge absorption D301 LED LED / Red, Green D302 Diode Quick discharge /AF mute D303 Zener diode Voltage reference

D304 Diode Voltage reference D305~310 D315~318 D319~321

TX-RX UNIT (X57-619X-XX)

Ref. No.

IC1,2 IC Buffer amplifier

IC10 IC Active filter / For HSDout

IC11 IC Active filter / For LSDin

IC12 IC FM IF system

IC13 IC Audio processor

IC14 IC PLL system

IC16 IC DTMF decoder

IC17 IC Flash memory

IC18 IC Active DBM

IC19 IC Microprocessor

IC20 IC EEPROM

IC21,22 IC Shift register / Output expander

IC23 IC Comparator (APC)

IC24 IC Analog switch

IC25 IC Active filter

Use/Function

LED LCD back light Diode Reverse current prevention Zener diode Surge absorption

Use/Function

IC3 IC Voltage detector / Reset IC4 IC Buffer amplifier IC5 IC Voltage regulator / 5M IC6 IC Voltage regulator / 5V IC7 IC Buffer amplifier IC8 IC D/A converter (Adjustment) IC9 IC Voltage regulator / 5C

Q1 Transistor Switch Q2 FET DC switch / 5R Q3 Transistor DC switch / 5T Q4 Transistor Noise amplifier / Squelch Q5 FET DC switch / Save Q6 Transistor 2nd IF W/N switch sets to on when Narrow

Operation/Condition

/ LCD back light LED AVR

Operation/Condition

TK-285/(N)

Ref. No.

Q10 Transistor AF mute switch Q11 FET Mute switch Q12 Transistor IF amplifier Q13 FET Mute switch / MIC line mute Q14 FET DC switch Q15 FET DET mute Q16 Transistor PLL IC fin amplifier Q17 FET Mute switch / MIC line mute Q18 Transistor Buffer amplifier Q19 Transistor Clock frequency shift Q20 Transistor RF amplifier / TX driver Q21 FET DC switch Q22 Transistor DC switch Q23 FET DC switch Q24 FET RF amplifier Q25 Transistor DC switch

D10 Diode Overload protection

D11 Diode Speed up D12,14 Diode ANT switch D16,17 Diode Varactor tuning D18,19 Diode Surge absorption D20,21 Diode Varactor tuning

D22 Diode ANT switch

D23 Diode TX/RX switch

D24 Diode Voltage drop

D401 Diode ANT switch D402 Diode Discharge

SUB UNIT (X58-473X-XX)

Ref. No.

Q2,3 FET VCO oscillation

D1-D8 Diode Frequency control

Use/Function

Q7 Transistor 2nd IF W/N switch sets to on when Wide Q8 Transistor Ripple filter Q9 Transistor DC switch / W/N audio amplitude adjust

D1 Diode Reverse protection D2 Diode Overload protection D3 Diode Reverse current protection D4 Diode Noise detection D5 Diode RF switch (2nd IF wide/narrow) D6 Diode Current steering D7 Diode RF switch (2nd IF wide/narrow) D8 Diode Voltage clamp D9 Diode TX/RX switch

Use/Function

Q1 FET DC switch

Q4 Transistor DC switch Q5 Transistor RF Buffer amplifier

D9 Diode TX modulation

Operation/Condition

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