Kenwood TH-F6A-F7E, TH-F6A 7F Schematic

144/220/440MHz FM TRIBANDER / 144/430MHz FM DUAL BANDER

TH-F6A/F7E

SERVICE MANUAL

B51-8580-00 (S) 798

KNOB(PTT/MONI) (K29-9108-13)

KEY TOP (K29-9107-12)

WHIP ANTENNA (T90-0781-05):K (T90-0789-05):T,E

KNOB(ENC) (K29-5159-03)

KNOB(VOL) (K29-5150-03)

FRONT GLASS (B10-2685-13):T,E (B10-2723-13):K

CAP (B09-0615-23)

CABINET ASSY (A02-3620-13):T,E (A02-3719-13):K

CONTENTS

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

CIRCUIT DESCRIPTION .......................................................... 4

DESCRIPTION OF COMPONENTS....................................... 14

PARTS LIST............................................................................19

EXPLODED VIEW .................................................................. 32

PACKING ................................................................................ 33

ADJUSTMENT ........................................................................ 34

PC BOARD VIEWS

TX-RX UNIT (CONTROL SECTION) ...................................... 59

TX-RX UNIT ............................................................................ 65

TX-RX UNIT (VCO SECTION)................................................ 71

SCHEMATIC DIAGRAM ......................................................... 73

BLOCK DIAGRAM .................................................................. 81

LEVEL DIAGRAM ................................................................... 83

OPTIONS ................................................................................ 85

SPECIFICATIONS .................................................................. 86

TH-F6A/F7E

DISASSEMBLY FOR REPAIR

1. How to remove the case assembly from the chassis:

1. Remove 2 screws (1).

2. Remove 2 knobs (2) and 2 round nuts (3).

3. Remove the SP/MIC jack cover (4).

4. Open the bottom part of case assembly and lift the front

panel from the chassis (5).

2. How to remove the main PCB:

2-1. Control section

1. Remove the SP/MIC jack cover (6).

2. Remove 5 screws (7) and lift and remove the control PCB

(TX-RX A/3).

3. Extract the encoder flat cable from the connector.

2-2. RF section

4. Remove 8 screws (8), and 1 round screw (9), then remove

the RF shield cover. Remove the soldering that connects the whip antenna and bar-antenna (3 locations).

5. Remove the battery terminal screw (0).

6. Lift and remove the RF PCB (TX-RX B/3).

2-3. PLL/VCO section

7. Remove the soldering (8 locations) that holds the PLL/VCO

shield cover (!) then lift the shield cover.

8. Lift the PLL/VCO PCB upward to seperate it from the main

PCB.

Fig. 1

DISASSEMBLY FOR REPAIR

TH-F6A/F7E

3. Soldering the Bar antenna wires

Before solding the bar antenna wires, form the wires as shown in the figure 2. Then solder the wires to lands on the PCB.

Fig. 2

5. Assembling a release latch

Place a coil spring(1) on the release latch(2) as shown in the figure 4. Then insert a shaft(3) into the release latch. Push the above assembly into the rear panel while the end of coil spring is hooked to the “A” tab.

Notch Notch

4. Removing a relay terminal

Insert a screw driver between the relay terminal and its holder. Then pull the relay terminal as shown in the figure 3.

Fig. 4

6. Caution at the time of reassembling

While you are reassembling the battery terminal holder (J19-5428) and the packing (G53-1532), confirm that the packing is reassembled at the condition that any swell is not occurred on it. If the packing is assembled with any swell, width of body also becomes expansive.

J19-5428

G53-1532

Swell not allowed

Fig. 3

Fig. 5

TH-F6A/F7E

CIRCUIT DESCRIPTION

1. A band receiver system

1-1. Receiver circuit

The A band can receive signals in two bands: VHF (220 MHz band <K type only>) and UHF (K type: three bands). It uses FM receive mode only, and uses double conversion with the first IF of 59.85 MHz and the second IF of 450 kHz.

The first amplifier is divided into two bands: 137 MHz -

173.995 MHz (216 MHz - 260 MHz <K type only>) and 410 MHz

- 470 MHz. The incoming signal from the antenna passes through a low-pass filter and a duplexer, and goes to an independent amplifier (Q63, Q62) for each band.

1-1-1. VHF band frontend

The incoming signal from the antenna passes through a VHF band low-pass filter and a duplexer, passes through a band-pass filter where it is tuned with varicaps (D76, D77), and goes to the first amplifier (Q63). Unwanted signal components are eliminated by a two-pole band-pass filter where it is tuned by varicaps (D72, D75, D81, D83), and the signal goes to the common mixer (Q45) for the A band. (K type only: For 200MHz band reception, D74 is turned off with a control signal to improve band-pass filter coupling and ensure pass bandwidth.)

ANT

BPF

LPF

D76 D77

MPU

RFAMP BPFBPF

Q63

3SK320

APC&VTUNEA

D72,D75 D81,D83

MIX

Q45

MT6C

04AE

1st IF

59.85MHz

1-1-3. Circuits following IF

The signal heterodowned to the first IF of 59.85 MHz by the mixer (Q45) passes through a 15kHz MCF (XF2) and unwanted signal components are eliminated. The resulting signal is amplified by the IF amplifier (Q43) and goes to the FM IC (IC7). The FM IC heterodowns it to the second IF of 450 kHz. Then, the signal passes through a 15kHz external ceramic filter (CF4) and goes to the FM IC again. The signal amplified by the IF amplifier built into the IC is demodulated by the quadrature FM demodulation circuit using a discriminator (CD1) and converted into an audio signal and output.

The FM modulation signal output from the FM IC passes through a low-pass filter consisting of a resistor and a capacitor and is output to the control section. The demodulation signal input to the control section goes to the electronic volume (IC706, pin 13) to adjust the audio balance with the B band. The output signal is amplified by the operational amplifier (IC717), passes through an active filter consisting of Q719 and Q717, and goes to the audio amplifier (IC707). The signal amplified to a higher power by the audio amplifier becomes the final output signal from the set and output through the internal speaker or speaker output pin (J701).

19.8MHZ

IFAMPMCF

Q43 2SC

5108(Y)

Q44 2SC

4915

AMP

IC717

4.50KHz

DE EMPHASIS

Q719 Q717

LPF

IC7

CF4

AUDIO

AMP

IC707

IC700

BAF

J701

MIX

Q45

MT6C

04AE

XF2

TCXO

Fig.1

1-1-2. UHF band frontend

The incoming signal from the antenna passes through a UHF band low-pass filter and enters the first amplifier (Q62) common to both A and B bands. The amplified signal is distributed by L distributors (L95, L96) and goes to the LC filter module (L92). Unwanted signal components are eliminated by the filter, and the resulting signal passes through another band-pass filter and enters the mixer (Q45).

ANT

BPF

LPF

HPF

RFAMP

3SK320

BPF

Q62

MIX

Q45

MT6C

04AE

L95 L96

LC FILTER

MODULE

1st IF

59.85MHz

Fig.2

L92

Fig.3

1-2. Mixer local oscillator

1-2-1. First mixer

The local oscillator signal for the first mixer is supplied from

the VCO-PLL circuit.

1-2-2. Second mixer

The local oscillator signal for the second mixer is a 59.4 MHz signal that is produced by multiplying the 19.8MHz TCXO (X1) oscillator output with a multiplier (Q44).

2. B band receiver system

2-1. Receiver circuit

The B band has a broadband receiver circuit configuration and implements broadband reception of 100 kHz to 1.3 GHz. FM/AM/SSB/CW reception is possible in the range 100 kHz to

29.7 MHz, and FM/wide FM/AM/SSB/CW reception is possible in the range 29.7 MHz to 1.3 GHz. The FM/AM receiver circuit uses double conversion with the first IF of 57.6 MHz and the second IF of 450 kHz. The SSB/CW receiver circuit uses triple conversion with the first IF of 57.6 MHz and the second IF of 450 kHz. The wide FM receiver circuit uses single conversion with the IF of 10.8 MHz.

CIRCUIT DESCRIPTION

TH-F6A/F7E

The first amplifier is divided into four bands: 100 kHz - 50 MHz, 50MHz - 108MHz, 108 MHz - 265 MHz, 265 MHz - 600 MHz, and 600 MHz - 1.3 GHz. The incoming signal from the antenna passes through a low-pass filter and a duplexer, and goes to an independent amplifier for each band. Then, the signal goes to the second common broadband amplifier (IC10) and its output is fed to the mixer (Q28) and heterodowned to the first IF.

2-1-1. FM/AM receiver circuit

The signal heterodowned to the first IF of 57.6MHz passes through a 15kHz MCF (XF1), and unwanted signal components are eliminated. The resulting signal is amplified by the IF amplifier (Q26) and goes to the FM IC (IC5). The FM IC heterodowns it to the second IF of 450 kHz. In FM mode, the signal passes through a 12.0kHz external ceramic filter (CF3) and goes to the FM IC. The signal amplified by the internal IF amplifier is demodulated by the quadrature FM demodulation circuit using a coil (L19) and converted into an audio signal and output. In AM mode, the signal passes through a 4kHz external ceramic filter CF1 and goes back to the FM IC. It is amplified by the AM AGC amplifier built in the FM IC, an audio

Q27 2SC

4915

OSCILLATOR

IF AMP

Q26 2SC

4915

Q24 2SC

4915

450KHz

UHF(600~1300)

UHF(265~600)

VHF(108~265)

TUNE

D29 HVC

376B

19.05MHZ

FINE1

AMP

IC10

MPC2746TB

MIX

Q28

MT6C

03AE

MCF

57.6MHz XF1

CF5

10.8MHz

output from the FM IC as an audio signal.

2-1-4. AM bar antenna receiver circuit

This unit incorporates an AM bar antenna, and either the bar antenna or the supplied antenna can be selected in the 520kHz-1.8MHz (SW) and 3.5MHz-10.1MHz (MW) bands (the initial value: bar antenna). The bar antenna has two kinds of tuners for SW and MW tuning, one of which is selected with a switching FET (Q32, Q48, Q52). The antenna is tuned with a varicap (D60) for AM tuning to select a desired signal. The signal from the bar antenna is amplified by and its impedance is converted by the buffer amplifier (Q59), and the resulting signal goes to the common mixer (Q28) for the B band. The signal is routed over the same path for AM demodulation as for the supplied antenna after leaving the mixer.

TUNE

D60

KV1566J

Q6,Q4

RF AMP

3SK320

BAR ANT

Q48,52

2SK1824

Q32

2SK1830

Q59

signal demodulated by the diode detection circuit is output.

2-1-2. SSB/CW receiver circuit

In SSB/CW mode reception, the signal takes the same path to CF1 as in AM mode. The signal input to the FM IC again is amplified by the AM AGC amplifier in the FM IC, then output from the AM IF output pin. The signal is fed to the third mixer (IC4) and converted to an audio signal and output.

2-1-3. Wide FM receiver circuit

The signal converted to the first IF of 10.8 MHz passes through a ceramic filter CF5 for wide FM, and is amplified by the IF amplifier (Q24). The signal passes through ceramic filter CF2 again to eliminate unwanted signal components, and goes to the FM IF input (pin 7) of the FM IC. The input signal is amplified by the IF amplifier in the IC, demodulated by the quadrature FM demodulation circuit using an L18 coil, and

SMB SQB

Q22,29

D25 DAN 235E

SSB/CW

UPA672T

SSB DET

IC4

TA4101F

OSCILLATOR

Q23

LMX

453KHz

TUNE

D20,24

KV1566J

IC5

TK10931V

CF1

CF3

CF2

10.8MHz

Fig.4

2-1-5. Audio signal

The FM and AM demodulation signals output from the FM IC (IC5) pass through a low-pass filter consisting of a resistor and a capacitor, and goes to the switching FET (Q29), from which a switched signal is output to the control unit. The SSB/CW demodulation signal passes through an RC LPF, connects to the Q29 output section, and output to the control unit through a line common to all modes. The demodulation signal input to the control unit goes to the electronic volume (IC706, pin 16), the audio balance output with the A band is restricted, then the signal is output. It joins the A band demodulation signal and is processed in the same manner for both A and B bands.

D57

HSC277

AMP

IC10

MPC2746TB

MIX

Q28

MT6C

03AE

FINE2

Fig.5

TH-F6A/F7E

CIRCUIT DESCRIPTION

SMB SQB

D25 DAN 235E

10.8MHz

FINE2

TUNE

D20,24

KV1566J

IC706

M62364

453KHz

OSCILLATOR

Q23

LMX

Fig.6

SSB DET

IC4

TA4101F

Q22,29

UPA672T

SSB/CW

2-2. Mixer local oscillator

2-2-1. First mixer

The local oscillator signal for the first mixer is supplied from the VCO-PLL circuit. To offset according to modes, the PLL switching frequency changes in FM/AM/CW, USB, LSB.

1st LOCAL (PLL Switching Frequency)

FM/AM CW USB LSB

UPPER Per 5kHz FM-2.5kHz FM-4.5kHz FM-0.5kHz

LOWER Per 5kHz FM-2.5kHz FM-4.5kHz FM-0.5kHz

* PLL Switching Frequency changes with the modes.

Table.1

2-2-2. Second mixer

The local oscillator signal of the second mixer uses

57.15MHz which is three times as high as the 19.05MHz crystal oscillator (X3) output. This local oscillator signal is used to (i) implement fine steps during fine tuning and (ii) offset during SSB/CW reception.

2rd LOCAL (Oscillator Frequency)

FM/AM

UPPER 57.15MHz

LOWER 57.15MHz

* During fine tuning, it changes with 33.3 Hz step from PLL

Switching Frequency to the next Switching Frequency.

(i) Fine tuning function

When the fine tuning function is ON, the PLL comparison frequency is 5 kHz (5kHz step). The "receive frequency of 10Hz steps as a set" is implemented by operating the local oscillator signal of the second mixer in 33.3Hz steps in the 5kHz frequency range. The frequency is varied by 57.15 MHz +/- 2.5 kHz by changing the voltage applied to the varicap (D29) installed in the local oscillator circuit.

(ii) Mode offset

The IF frequency is adjusted by 2 Hz in SSB mode so that the demodulated signal passes through the center of the 4kHz ceramic filter (CF1). The frequency is adjusted by varying the local oscillator frequency.

CW(Fine Tuning)

57.15MHz+2.5kHz

Oscillator Frequency

57.15MHz-2.5kHz

USB(Fine Tuning) LSB(Fine Tuning)

PLL Switching Frequency

Table.2

57.15MHz-2.5kHz

57.15MHz+2.5kHz

IC5

TK10931V

2-2-3. Third mixer

The third mixer (IC4) works in SSB/CW mode only. The local oscillator signal of 450 kHz +/- 2 kHz is produced in SSB mode to restore 2kHz correction (offset), and the signal of 450

CF1

CF3

kHz - 800 Hz is produced to generate an 800Hz beat frequency in CW mode. A demodulation signal is produced in SSB, and a 800Hz beat signal is produced in CW.

450KHz

3rd LOCAL (Oscillator Frequency)

FM/AM CW USB LSB

CF2

UPPER 450kHz

LOWER 450kHz

450kHz+800Hz 450kHz+2kHz 450kHz-2kHz

450kHz+800Hz 450kHz-2kHz 450kHz+2kHz

* Perform Mode OFFSET

Table.3

2-3. AGC circuit

The AGC is controlled by using the output from the RF AGC built into the FM IC (IC5). The AGC is controlled by controlling the bias current of the IF amplifier (Q26) and the forward current of the pin diode (D32) for the attenuater. In non-FM mode, the AM AGC circuit built-into the FM IC is also used.

3. Control

3-1. Reset and backup circuits

The CPU reset signal is generated with the CR time constant by detecting a rising edge of the M4 line voltage with the voltage detection IC (IC709). If the voltage supplied to the THF6/TH-F7 decreases and the M4 line voltage falls below the detection voltage of the voltage detection IC (IC710), the CPU (IC705) detects it through the interrupt pin, backs up data in the EEPROM (IC704), and shuts the power off.

3-2. Voltage detection processing

The voltages are measured through the A/D port of the CPU (IC705) for processing. The battery voltage is supplied through a resistor, and a warning sound is produced when an abnormal power supply voltage (17.5 to 22.0 V) is applied to the battery meter during transmission. The squelch voltage is input from the IF IC, and a change in the noise voltage is detected to control squelch. The S meter voltage is input from the IF IC to control the S meter display. Thermistor voltage (temperature) detection, remote control microphone key operation, VOX voltage monitoring, and TONE/DCS decoding are performed through the A/D port.

3-3. VOX

The signal output from the microphone amplifier (IC702) is amplified by Q701, rectified/integrated by D709 to convert to DC voltage, and monitored through the A/D port of the CPU (IC705) to perform VOX processing.

3-4. Battery save

The CPU (IC705) controls Q728 through the SAVE port to save battery power.

3-5. LED drive circuit

The CPU (IC705) controls Q709 to turn LEDs on to illuminate the LCD and keys. The ON AIR/BUSY LED is directly controlled through the open drain port of the CPU (IC705).

CIRCUIT DESCRIPTION

TH-F6A/F7E

3-6. Key/encoder input circuit

The PWR key is assigned to an interrupt port. The PTT key is assigned to another interrupt port. The other keys and destination diodes form a 5x6 matrix and pressing a key is detected by scanning the matrix by software. The encoder reads data through the interrupt port.

3-7. CTCSS/DCS

The encode signal is output from the D/A port of the CPU (IC705) by software. The signal level is adjusted with an electronic VR (IC706) and the signal is divided into VCO and TCXO and modulated like a 9600bps packet signal.

The audio signal from the IF IC passes through the IC712/ IC711 waveform rectification circuit and enters the A/D port of the CPU (IC705). The CPU detects that the specified CTCSS tone frequency and DCS code are detected and controls muting.

4. PLL • VCO

The TH-F6/TH-F7 has two PLL loops and a total of four VCOs, two for each PLL loop. The PLL is divided for A band reception, B band reception and transmission. Each VCO has oscillator frequency shift control. For relationships between VCO oscillator frequencies and shifts, see Table 4-11.

3-8. DTMF

The DTMF signal is output from the D/A port of the CPU (IC705) by software means. The signal is mixed with a signal at the input side of the audio amplifier (IC707) and output as a monitor tone. It is mixed with a modulation signal at the input side of the preemphasis (IC701) and used to as a transmit signal.

3-9. Serial control

The REM/PTT terminal of the speaker mic jack (J701) is switched by the CPU (IC705) and functions as TXT/RXD to communicate with a personal computer.

TH-F6A Frequency Construction A band RX Double Super Heterodyne

Audio

RX Freq. Range [MHz]

137.000 173.995 196.850 233.845 Upper 59.85 59.4 Lower 450

216.000 259.995 275.850 319.845 Upper 59.85 59.4 Lower 450

410.000 469.995 350.150 410.145 Lower 59.85 59.4 Lower 450

TH-F6A Frequency Construction TX

2nd

Mixer

1st IF Amplifier1st Mixer2nd IF

VCO2nd LO

Fig.7

1st IF

VCO Oscillation [MHz]

1st Mix.

[MHz]

2nd LO [MHz]

Table.4

VCO Devider Amplifier

Fig.8

Transmission Frequency Range

Band

[MHz]

[MHz] Devide

144 144.000 147.995 576.000 591.980 4

220 222.000 224.995 444.000 449.990 2

440 438.000 449.995 438.000 449.995 1

VCO Oscillation [MHz]

2nd Mix.

2nd IF [kHz]

Table.5

TH-F6A/F7E

* TH-F6A Frequency Construction B band RX FM mode Double Super Heterodyne

CIRCUIT DESCRIPTION

Audio

2nd IF

2nd

Mixer

2nd LO VCO

1st IF

1st

Mixer

Devider

Multiplyer

Amplifier

Fig.9

1st IF

RX Freq. Range [MHz] VCO Oscillation [MHz] 1st LO

0.100 22.995 461.600 644.760 1 8 57.700 80.595 Upper 57.6 57.15 Lower 450

23.000 103.995 322.400 646.380 1 4 80.600 161.595 Upper 57.6 57.15 Lower 450

104.000 266.995 323.200 649.190 1 2 161.600 324.595 Upper 57.6 57.15 Lower 450

267.000 409.995 324.600 467.595 1 1 324.600 467.595 Upper 57.6 57.15 Lower 450

410.000 469.995 352.400 412.395 1 1 352.400 412.395 Lower 57.6 57.15 Lower 450

470.000 591.995 527.600 649.595 1 1 527.600 649.595 Upper 57.6 57.15 Lower 450

592.000 706.995 534.400 649.395 1 1 534.400 649.395 Lower 57.6 57.15 Lower 450

707.000 707.995 382.300 382.798 2 1 764.600 765.595 Upper 57.6 57.15 Lower 450

708.000 851.995 325.200 397.198 2 1 650.400 794.395 Lower 57.6 57.15 Lower 450

852.000 868.995 454.800 463.298 2 1 909.600 926.595 Upper 57.6 57.15 Lower 450

869.000 896.995 405.700 419.698 2 1 811.400 839.395 Lower 57.6 57.15 Lower 450

897.000 922.995 477.300 490.298 2 1 954.600 980.595 Upper 57.6 57.15 Lower 450

923.000 938.995 432.700 440.698 2 1 865.400 881.395 Lower 57.6 57.15 Lower 450

939.000 1009.995 498.300 533.798 2 1 996.600 1067.595 Upper 57.6 57.15 Lower 450

1010.000 1299.995 476.200 621.198 2 1 952.400 1242.395 Lower 57.6 57.15 Lower 450

Multiply Devide 1st Mix.

[MHz]

2nd LO

[MHz] 2nd Mix.

2nd IF

[kHz]

B band RX WFM mode Single Super Heterodyne

Audio

RX Freq. Range [MHz] VCO Oscillation [MHz] 1st LO

29.700 54.995 324.000 526.360 1 8 40.500 65.795 Upper 10.8

55.000 91.995 353.600 649.560 1 8 44.200 81.195 Lower 10.8

92.000 130.795 324.800 479.980 1 4 81.200 119.995 Lower 10.8

130.800 150.995 566.400 647.180 1 4 141.600 161.795 Upper 10.8

151.000 309.995 323.600 641.590 1 2 161.800 320.795 Upper 10.8

310.000 449.995 320.800 460.795 1 1 320.800 460.795 Upper 10.8

450.000 659.995 439.200 649.195 1 1 439.200 649.195 Lower 10.8

660.000 1299.995 324.600 644.598 2 1 649.200 1289.195 Lower 10.8

Table.6

1st IF

VCO

1st

Mixer

Devider

Multiplyer

Amplifier

Fig.10

Multiply Devide 1st Mix.

Table.7

1st IF

[MHz]

* TH-F7 Frequency Construction A band RX Double Super Heterodyne

TH-F6A/F7E

CIRCUIT DESCRIPTION

Audio

RX Freq. Range [MHz]

144.000 145.995 203.850 205.845 Upper 59.85 59.4 Lower 450

430.000 439.995 370.150 380.145 Lower 59.85 59.4 Lower 450

TH-F7 Frequency Construction

2nd

Mixer

VCO Oscillation [MHz]

1st IF Amplifier1st Mixer2nd IF

Fig.11

1st Mix.

Table.8

1st IF [MHz]

VCO2nd LO

2nd LO [MHz]

2nd Mix.

2nd IF [kHz]

Fig.12

Transmission

Band

Frequency Range

[MHz] Devide

[MHz]

144 144.000 145.995 576.000 583.980 4

440 430.000 439.995 430.000 439.995 1

VCO Oscillation [MHz]

Table.9

TH-F6A/F7E

* TH-F7 Frequency Construction B band RX FM mode Double Super Heterodyne

CIRCUIT DESCRIPTION

Audio

2nd IF

2nd

Mixer

2nd LO VCO

1st IF

1st

Mixer

Devider

Multiplyer

Amplifier

Fig.13