Kenwood TH-K2AT, TH-K2E, TH-K2ET Service Manual

144MHz FM TRANSCEIVER

TH-K2AT/K2E/K2ET

SERVICE MANUAL

B51-8658-00 (S) 836

Helical Antenna (T90-1018-25)

Knob (PTT/LAMP/MON) (K29-9274-03)

Key top (16key) (K29-9272-02)

Knob (ENC) (K29-5159-03)

Knob (VOL) (K29-5150-03)

Front glass (B10-2746-03)

Cap (SP/MIC/DC IN) (B09-0675-03)

Cabinet assy (16key) (A02-3819-23)

Helical Antenna (T90-1018-25)

Knob (PTT/LAMP/MON) (K29-9274-03)

Key top (4key) (K29-9276-02)

Knob (ENC) (K29-5159-03)

Knob (VOL) (K29-5150-03)

Front glass (B10-2746-03)

Cap (SP/MIC/DC IN) (B09-0675-03)

Cabinet assy (4key) (A02-3818-23)

TH-K2AT/K2ET TH-K2E

CONTENTS

DISASSEMBLY FOR REPAIR ...................................2

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

SEMICONDUCTOR DATA ...................................... 14

COMPONENTS DESCRIPTION ..............................15

PARTS LIST.............................................................17

EXPLODED VIEW....................................................23

PACKING ................................................................. 25

ADJUSTMENT ........................................................ 27

TERMINAL FUNCTION........................................... 43

PC BOARD

TX-RX UNIT (X57-674X-XX) (A/3) ................... 44

TX-RX UNIT (X57-674X-XX) (B/3),(C/3) ..........48

SCHEMATIC DIAGRAM..........................................50

LEVEL DIAGRAM.................................................... 55

BLOCK DIAGRAM................................................... 56

BC-21 (WALL CHARGER) .......................................58

PB-43N (Ni-MH BATTERY PACK) ..........................58

BT-14 (BATTERY CASE) ......................................... 59

PG-4Y (PROGRAMMING INTERFACE CABLE) .....59

MCP-1A (MEMORY CONTROL PROGRAM) ......... 59

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

TH-K2AT/K2E/K2ET

CN2

CN9

CN6

√

∫

Ω

∫

≈

≤

TX-RX unit (B/3)

TX-RX unit (C/3)

TX-RX unit (A/3)

DISASSEMBLY FOR REPAIR

How to remove the case assembly from the chassis

1. Remove two screws (z) holding the chassis.

2. Pull out two knobs (

3. Pull out the SP and MIC parts of the cap from jacks (

4. Turn the unit over with the bottom of the chassis facing upwards, and remove the chassis ( assembly (

5. Remove the speaker lead ( the TX-RX PC board (TX-RX unit A/3).

) and remove two round nuts (c).

) from the case

) from the connector (CN2) of

How to remove the PC board

■ Numeric key PC board (TX-RX unit B/3)

1. Remove three screws (,) on the numeric key PC board.

2. Lift the numeric key PC board and remove it from the

■ PTT PC board (TX-RX unit C/3)

3. Remove one screw on the PTT PC board (/).

4. Pull the PTT PC board to the left and remove it from the

■ TX-RX PC board (TX-RX unit A/3)

5. Remove the SP/MIC jack cover (≈).

6. Remove two screws (

7. Remove two screws (

8. Remove eight screws (

9. Absorb solder from the antenna terminal (

Note: Do not melt the shadow plate (

10.Remove the TX-RX PC board from the chassis, then remove

connector (CN9) of the TX-RX PC board (

connector (CN6) of the TX-RX PC board (TX-RX unit A/3) (

Ω

) holding the shield

cover (antenna terminal section).

) holding the shield

√

cover (final amplifier section).

board.

with a solder absorber.

) on the TX-RX PC

∫

moving the tip of the solder absorber close to the antenna terminal.

the encoder volume FPC ( of the TX-RX PC board.

) from the flat cable connector

≤

) when

)

TH-K2AT/K2E/K2ET

DISASSEMBLY FOR REPAIR

Soldering the antenna terminal

1. With the shield cover removed from the antenna terminal section, install two screws on the PC board and bring the PC board into contact with the chassis (

2. Solder the antenna terminal with a soldering iron (

3. Remove the two screws installed in step 1 above, and install the two screws again on the PC board together with the shield cover (

4. Apply the tips of soldering irons to all the four pins of the final FET at the same time ( the final FET (

). (Two persons should be required to do this.)

5. Remove all PC boards from the chassis.

6. Confirm that there is no space between the radiation plate installed on the foil side of the TX-RX PC board (TX-RX unit A/3) and the PC board ( the radiation plate and PC board, eliminate it by applying the tip of the soldering iron to the radiation plate.

), heat them sufficiently, and remove

). If there is any space between

Radiation plate

TX-RX PC board

Replacing the final FET (Q12)

1. Remove the two screws holding the shield cover of the final FET section (

2. Remove solder from the shield cover completely with a solder absorber. (E and E3 types only)

3. Remove the shield cover (

7. Apply the tip of the soldering iron to the installation side of the radiation plate of the TX-RX PC board, put a little amount of solder to the radiation plate that is seen through a square hole in the final FET installation section and melt the solder (

8. When the solder in step 7 is melted, place the final FET on the PC board by aligning it with the silk of the final FET installation section of the PC board (

9. Release the soldering iron and confirm that the final FET

and radiation plate have been soldered.

10.Solder the four pins of the final FET with the soldering iron.

11.Install all the PC boards.

12.Reinstall the shield cover removed in step 3 above in its

original position and install two screws.

13.Solder the shield cover to the PC board. (E and E3 types

only)

14.

Install the chassis on the case assembly and assemble them.

15.Readjust transmission power.

Note: Since the FET is sensitive to static electricity, always

wear a grounding band. Use a highly insulated ceramic heater solder iron.

TH-K2AT/K2E/K2ET

DISASSEMBLY FOR REPAIR

Special care and attention required for assembly

1. Gluing to the key top (MIC element section)

You must also glue on the speaker storage area and heap the glue up until wealthy glued on the speaker storage area and the key top for waterproofing the MIC element side of the key top. (Fig. 1)

Heap the glue up until wealthy glued on the speaker storage area and the key top (MIC element section).

Fig. 1

Bending the LCD hardware fixture (J21-8456-03) tabs

(1)Insert the tabs of the LCD hardware fixture into four holes

in the LCD installing position of the TX-RX PCB (TX-RX unit

A/3). (Fig. 2)

Fig. 2

(2)By pressing the LCD hardware fixture from the component

side of the TX-RX PCB, you must bent all 4 tabs of the LCD hardware fixture being visible from the foil side until the bases of each tabs are folded at least 45 degrees (Fig. 3). If the bending angle of the tabs of the LCD hardware fixture is less than 45 degrees, a display error may occur.

Min 45 degrees

Bending position

NG NG

Fig. 3

3. PTT PCB (TX-RX unit C/3) installation procedure

Installing the PTT PCB on the TX-RX PCB and chassis are as follows: (1)Insert the PTT PCB connector (CN7) into the TX-RX PCB

connector (CN6) lightly. (2)Push three parts of the PTT PCB to contact tightly with the

chassis. There may be a small gap between the connectors.

(Fig. 4) Note: A double-side adhesive tape (J99-0376-04) is used

behind the PTT switch. When reassembling the PTT PCB to the chassis, press the PTT PCB (under the PTT switch) so that the tape hold the PCB and chassis securely.

Chassis

PTT switch

Push three parts of the PTT PCB to contact tightly with the chassis.

PTT PCB (C/3)

CN6

A bit clearance

CN7

Chassis

PTT switch

PTT PCB (C/3)

CN6

No clearance

CN7

Fig. 4

(3)Tighten one screw in the PTT PCB.

TH-K2AT/K2E/K2ET

LAMP

PTT

DISASSEMBLY FOR REPAIR

4. Packing (G53-1572-02) TX/BUSY lamp installation procedure

(1)To assure waterproofing, install the packing in the chassis

groove as shown in Fig. 5. (

(2)Install the packing TX/BUSY lamp section on the chassis.

(

)

Packing

Chassis

Packing

Chassis

)

Cautions for installing the chassis on the case assembly

(1)Verify that the packing (G53-1572-02) TX/BUSY lamp section

is has been past through the hole in the illumination guide section on the top of the case assembly. (Fig. 7)

The packing TX/BUSY lamp section is has been past through the hole in the illumination guide section on the top of the case assembly.

Fig. 7

(2)Align the speaker lead as shown fig.8. Do not place the

leads over the key top section, LCD section or SP/MIC/DC IN cap section.

Fig. 5

Packing (G53-1572-02) bottom installation procedure

(1)Before installing the numeric key PCB (TX-RX unit B/3) on

the chassis, push three parts of the packing to contact tightly with the chassis as shown in Fig. 6. If the packing is not in contact with the chassis, there may be a gap between the transceiver bottom case assembly and the battery, and water may enter through the gap.

OK NG

Push three parts of the packing to contact tightly with the chassis.

Clearance NG

Fig. 6

Do not fix this part of the key top to the rib of the case assembly.

Fig. 8

Cautions for installing the key top on the case assembly

(1)Install the key top keypad section and the power switch

section on the rib of the case assembly.

(2)Do not fix the part between the key top keypad section and

the power switch section to the rib of the case assembly, but install it as shown in Fig. 8.

TH-K2AT/K2E/K2ET

CIRCUIT DESCRIPTION

Frequency Configuration

The frequency configuration is shown in Figure 1 and

Table 1.

136.000~173.995MHz(K,K2,M,M2)

RX :

144.000~145.995MHz(E,E3)

TX :

ANT

FINAL

DRIVE

144.000~147.995MHz(K,K2)

136.000~173.995MHz(M,M2)

144.000~145.995MHz(E,E3)

1st MIX

AMP

PRE

DRIVE

144.000~147.995MHz(K,K2)

136.000~173.995MHz(M,M2)

144.000~145.995MHz(E,E3)

38.85MHz

174.850~212.845MHz (K,K2,M,M2)

182.850~184.845MHz (E,E3)

MCF

450kHz

MIX, IF,

DET

Tripler

x 3

PLL

VCO

38.4MHz

AMP

TCXO

MIC

AMP

12.8MHz MIC

Fig. 1 Frequency configuration

Double super heterodyne

Reception method 1st IF Frequency 38.85MHz (Upper)

2nd IF Frequency 450kHz (Lower)

Transmission method

VCO direct oscillation amplification

Modulation Variable reactance phase modulation

Table 1 Basic configuration

Receiver System

■ Front End

The received signal from the antenna passes through a lowpass filter and then through a transmission/reception switching circuit (antenna switch) and enters the band-pass filter (L40, L41, L38).

The signal passing through the band-pass filter (L40, L41, L38) is amplified by with an RF amplifier (Q17), passes through a band-pass filter (L32, L35) and enters the first mixer (Q16).

These band-pass filters are tuned to a desired frequency by varicaps (D21, D20, D19, D18).

A tuning voltage corresponding to the desired signal is applied to each varicap through the BPF/APC terminal (pin 6) of the MPU (IC8) to tune to the receive frequency.

■ First Mixer

The received signal passing through the band-pass filter (L32, L35) is mixed with the first local signal generated by the VCO by the first mixer (Q16) to produce a first IF signal (38.85 MHz) (Upper heterodyne).

The first IF signal passes through a MCF (Monolithic crystal filter: XF1) to remove unwanted components.

The first IF signal passing through the MCF (XF1) is amplified by an IF amplifier (Q24) and the resulting signal enters the FM IC (IC3).

Item Rating

Nominal center frequency (fo) 38.85MHz Pass bandwidth ±6.0kHz or more at 3dB Attenuation bandwidth ±25kHz or less at 35dB Ultimate attenuation 70dB or more (fo –910 kHz) Spurious response 40dB or more (fo +1MHz) Ripple 1dB or less Insertion loss 4dB or less Terminating impedance 610Ω ±5% // 3pF ±0.5pF

Table 2 MCF (L71-0619-05) characteristics (TX-RX unit XF1)

Item Rating

Nominal center frequency (fo) 450kHz 3dB bandwidth ±6.5kHz or more 50dB bandwidth ±15.5kHz or less Ripple 2dB or less (fo ±6.5kHz)

55dB or more

Guaranteed attenuation (fo ±18kHz to ±33kHz)

50dB or more (fo ±100kHz) Insertion loss 4dB or less I/O matching impedance 1.5kΩ

Table 3 Ceramic filter (L72-0968-05) characteristics (TX-RX unit CF1)

ANT

BPF

L41,L40,L38

ANT

Tuning voltage

PLL

LPF

VCO

RF AMP

Q17

D20D21

BPF/APC

MPU

IC8

Fig. 2 Receiver section configuration

D19

BPF

L32,L35

MIXER

D18

Q16

MCF

XF1

38.85MHz

1st Local OSC

(PLL)

IF AMP

Q24

5R5R

FM IC

IC3

IF AMP,

DET

2nd Local OSC

Tripler

x 3

TCXO

12.8MHz

AF AMP

IC6

Q23

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