Service_Manual_TTI_TCB-770_ENG.pdf

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1、SERVICE MANUAL MULTI CHANNEL AM/FM TRANSCEIVER TCB-770 TTI Tech Downloaded from www.cbradio.nl SECTION1SPECIFICATIONS SECTION2CIRCUIT DESCRIPTION 1GENERAL 2TECHNICAL DESCRIPTION 3SEMICONDUCTORS AND FUNCTION 4DESCRIPTION OF FREQUENCY DETERMINING AND STABILIZING CIRCUIT 5TEST EQUIPMENT SETUP AND ALIGN

2、MENT INSTRUCTIONS SECTION 5-3LED PCB 3PART LIST SECTION 5-1MAIN PCB 5-2 5-4VOLUME PCB 5-5MIC PCB FRONT PCB 4MECHANICAL DISASSEMBLY SECTION5BOARD LAYOUT SECTION6BLOCK DIAGRAM SECTION7SCHEMATIC TABLE OF CONTENTS Channel Frequency Range Operating mode Frequency Control Frequency Tolerance Operating Tem

3、perature Range Microphone Input Voltage Size Weight Antenna Connector Power Output Modulation Frequency Response Output Impedance Harmonic Suppression Current Drain Receiving System IF Frequencies Sensitivity Audio Output Power Audio Distortion Image Rejection Adjacent Channel Rejection Conducted Sp

4、urious Frequency Response Built-in Speaker Squelch * Specification is subject to change without prior notice. T R A N S M I T T E R R E C E I V E R G E N E R A L 40 (See the frequency band chart) 26.96 MHz 27.99125 MHz F3E (FM), A3E (AM) PLL Synthersizer 0.002% -10 to + 55 C Plug-in Type 13.2V DC 15

5、% 140 (W) x 186 (L) x 37 (H) 990 g Antenna Connector Duty cycle 10% 4 Watts 13.8V DC AM:from 85% to 95% FM:1.8KHz 0.2KHz 300Hz to 3000Hz 50ohms, Unbalanced More than -36dBm AM Full Mod. 1.6A Max. Dual conversion superheterodyne Double Conversion 1st 10.695MHz/2nd 455KHz 0.7 V for 10dB(S+N)/N in AM M

6、ode 0.5 V for 20dB SINAD in FM Mode 2.0W 8 Ohm Less then 8% 1KHz 60 dB 60 dB More than 60 dB 300 to 2500Hz 8 Ohms, round Adjustable; Threshold less than 1 microvolt SECTION1 SPECIFICATIONS - Contents - 1 General 1-1. Receiver 1.2. Transmitter 2. Technical Description 2-1. General 2-2. Type of emissi

7、on 2-3. Frequency Table 2-4. RF Power Output 2-5. DC input Voltage and Current with 13.2V DC Input to Power AMP 2-6. Receiver IF and Local Oscillator Frequencies 3. Semiconductors and Function 4. Description of Frequency Determining and Stabilizing Circuit 4-1. Introduction 4-2. Basic Synthesis Sche

8、me 4-3. Descriptions of Each Block 4-3-1. Introduction 4-3-2. Reference Frequency 4-3-3. VCO 4-3-4. Programmable Divider and its Control 4-3-5 Phase Detector and VCO Control 4-3-6. Transmitter / Receiver Buffer AMP 4-3-7. Transmitter Doublers 4-3-8. Switching of Turning Capacitor in VCO 4-3-9. Recei

9、ver Local Oscillator Outputs 4-4. Frequency Stability 4-5. Description of other Circuits 4-5-1. Transmitter 4-5-2. Receiver 5. Test Equipment Setup and Alignment Instructions 5-1. General Section 5-2. Transmitter Section 5-3. Receiver Section SECTION2 CIRCUIT DESCRIPTION 1. General 1-1. Receiver Dis

10、play : 40 Channels and other functions indication Frequency Range : 26.965 to 27.405 MHz Frequency Response : 300 to 2,500 Hz Power Source : 13.2 V DC Audio Output Load : 8 OHM Audio Output : 4.0 W (or More) Squelch : Adjustable from 0.3uV to 100 uV Sensitivity : - FM : 20 dB SINAD under 1.0 uV RF S

11、ignal or less - AM :10 dB S/N under 1.0 uV RF Signal or less Intermediate Frequency : - 1st IF : 10.695 MHz - 2nd IF : 455 KHz 1-2. Transmitter Carrier Power(Conducted) : AM 1 W / FM 4 W Current Drain ( 13.2 V Supply Voltage) - No Modulation : 1,000 mA - Max Modulation : 1,400 mA Modulation Capabili

12、ties - AM : 90 % - FM : 1.8 KHz/Dev Spurious Radiation : Less then 72 dBc Antenna Impedance : 50 OHM Frequency Tolerance : 0.002 % 2. Technical Description 2-1. General Model CB-770 is an mobile type AM/FM radio transceiver for use of the Citizen Radio Service. ? Front Panel Controls LCD (Cannel and

13、 RX/TX Signal Level Indicator). Receiver Audio Control (With Power ON/OFF Control) Volume Squelch Control Volume RF Gain Control Volume MIC GAIN Control Volume CHANNEL UP/DOWN Rotary Switch EMG(Emergency Channel Select) Key AM/FM Select Key Scan Key Q.CHANNEL UP Key Q.CHANNEL DOWN Key ? Accessorily

14、Connectors Antenna Socket External Speaker Jack External Signal Meter Jack Microphone(Condenser Microphone) 2-2. Type of emission : AM(A3E) , FM(F3E) 2-3. Frequency Table Channel Frequency (MHz) Channel Frequency (MHz) 1 26.965 21 27.215 2 26.975 22 27.225 3 26.985 23 27.235 4 27.005 24 27.245 5 27.

15、015 25 27.255 6 27.025 26 27.265 7 27.035 27 27.275 8 27.055 28 27.285 9 27.065 29 27.295 10 27.075 30 27.305 11 27.085 31 27.315 12 27.105 32 27.325 13 27.115 33 27.335 14 27.125 34 27.345 15 27.135 35 27.355 16 27.155 36 27.365 17 27.165 37 27.375 18 27.175 38 27.385 19 27.185 39 27.395 20 27.205

16、40 27.405 2-4. RF Power Output ? AM : 1.0 W ? FM : 4.0 W 2-5. DC Iinput Voltage and Current with 13.2V DC Input to Power AMP ? Transmitter Power Amp : Voltage 12.5 V Current 727 mA ? Transmitter Driver Amp : Voltage 12.5 V Current 120 mA 2-6. Receiver IF and Local Oscillator Frequencies ? First IF :

17、 10.695 MHz ? Second IF : 455 KHz ? First Local Oscillator : 10.695 MHz Below Receiving Frequency ? Second Local Oscillation : 10.240 MHz 3. Semiconductors and Function 3-1. Transistor - Ref No. Description Manufacturer Function - Q101 KTC3880S KEC RX Amplifier Q102 KTK211 KEC 1st Mixer Q103 KTK211

18、KEC 1st Mixer Q104 KRC101S KEC RX Band1 Switching Q105 KRC101S KEC RX Band2 Switching Q121 KRC110S KEC Q122 KRC112S KEC RX RSSI Level Control Q151 KTC3875S KEC RX FM AF Amplifier Q152 KRC112S KEC FM AF Mute at AM Mode Q153 KRC101S KEC FM AF Mute at AM Mode Q154 KRC112S KEC RX AF Mute at TX Mode Q161

19、 KTC3880S KEC AM IF Amplifier Q162 KTC3880S KEC AM IF Amplifier Q163 KRA102S KEC RX AM B+ Q164 KTA1504S KEC Automatic Noise Level Control Q181 KTC3875S KEC RX RF Mute at TX Mode Q182 KTC3875S KEC AGC Q183 KTC3875S KEC AGC Q201 KRC101S KEC AF Mute Q202 KRC111S KEC AF Path Q233 KTA1504S KEC Automatic

20、Level Control Q234 KTC3875S KEC Automatic Level Control Q301 KTC3880S KEC VCO Q302 KTC3880S KEC RX/TX VCO Buffer Q303 KTC3880S KEC VCO Buffer Q305 KRC101S KEC TX VCO Control Q311 KRC101S KEC VCO Band1 Switching Q312 KRC101S KEC VCO Band2 Switching Q313 KRC101S KEC VCO Band3 Switching Q502 KRC111S KE

21、C FM TX AF Mute at AM TX Q701 KTC3880S KEC TX Doublers Q702 KTC3880S KEC TX Pre-Amplifier Q703 KTC1006 KEC TX Driver Amplifier Q704 2SC2078 SANYO TX Power Amplifier Q742 KTC3875S KEC TX RF Mute at RX Mode Q801 KRC104S KEC CPU Reset Q802 KRC101S KEC CPU RX/TX Control Q803 KRA101S KEC MIC Lock Control

22、 Q911 KTA1658 KEC Main Regulator Q912 KRA1504S KEC Main Regulator Q913 KRC112S KEC Main Regulator Control Q914 KRC102S KEC Power Low Control Q921 KTC3875S KEC 8.2V Regulator Q923 KTC3875S KEC RX B+ Q924 KRA1504S KEC TX B+ Q931 KTC3875S KEC Main Regulator5.6V Q941 KRC111S KEC Mute Q951 KTA1241 KEC Ba

23、ck Light LED Control Q952 KTA1241 KEC Back Light LED Control Q953 KRC101S KEC Back Light LED Control Q954 KRC101S KEC Back Light LED Control Q961 KRC110S KEC TX AF Mute at RX Mode Q962 KRC111S KEC MIC AF Path at AM Mode 3-2. IC - Ref No. Description Manufacturer Function - IC101 TK144889V TOKO IF IC

24、 IC102 KIA358F KEC AGC, Squelch Control IC201 KIA7217AP KEC AF Power Amplifier IC301 LC7152NM SANYO PLL IC401 KIA4558F KEC FM TX AF IC801 TMP87PP21DF TOSHIBA CPU IC802 24WC02 ATMEL EEPROM 3-3. Manufacture Information ? KEC - KEC Co., LTD. ? SANYO - SANYO Semiconductor Co., LTD. ? TOKO - TOKO, Inc. ?

25、 TOSHIBA - Toshiba Semiconductor. Co., LTD. ? ATMEL - ATMEL Co., LTD 4. Description of Frequency Determining and Stabilizing Circuit 4-1. Introduction The Frequencies for transmitter and receiver first local frequencies are all derived from a signal 4.5MHz crystal by means of a phase locked loop(PLL

26、). The first local oscillator frequencies are 16.270MHz(CH1) to 16.710MHz(CH40). The second local frequency is fixed at 10.240MHz to generate second IF 455KHz. Transmit, the VCO of the PLL operates 13.4825MHz(CH1) to 13.7025MHz(40CH). The VCO frequency goes to the doublers circuit Q701, L701, L702 w

27、ith doubles the frequency to generate 26.965MHz(CH1) to 27.405MHz(40CH). Q302 VCO Q701 Doublers 13.4825MHz(CH1) 13.7025MHz(CH40) 26.965MHz(CH1) 27.405MHz(CH40) To transmitter The VCO operating frequency for the receiver is 16.27MHz(CH1) to 16.710MHz(CH40) as the first local oscillator, injected thro

28、ugh the buffer amplifier Q302 into the first FET balanced mixer Q102, Q103. 4-2. Basic Synthesis Scheme The crystal frequency(4.5MHz) is divided by 1800 times to make 2.5KHz which is fed to one side of the phase detector. The VCO output is divided by a programmable divider, and fed to other side of

29、the phase detector Pin 9, 10 of IC301. Passing the phase detector output closes the feedback loop through an active low pass filter and using the output to control the VCO frequency through varicap diode D301. Under locked conditions, both of phase detector input signal must be identical at 2.5KHz.

30、The VCO frequency is then given by ; Receiver : Fvco / N = 0.005 MHz OR Fvco = 0.005 X N MHz Transmitter : Fvco / N = 0.0025 MHz OR Fvco = 0.0025 X N MHz Since “N” is an integer, the VCO frequency can be stepped up with in receiver mode 5KHz and transmitter mode 2.5KHz increments. By suitable choice

31、 of “N” the desired output frequency can be obtained. Channel 1 Channel 40 N Fvco N Fvco Transmit 5393 13.4825 5481 13.7025 Receiver 3254 16.2700 3342 16.7100 See the Table 1for other Channels The VCO frequency goes to the doublers circuit, with doubles the incoming signals. VCO Output Frequency Dou

32、blers Output Frequency Transmit - - - Transmit CH 1 , 13.4825 MHz CH 40 , 13.7025 MHz 26.965 MHz 27.405 MHz Since all frequencies are obtained from the crystal controlled PLL oscillator, all outputs are coherent with the crystal oscillator frequency and matching the sample percentage accuracy. Note

33、that the reference frequency of 5KHz(receiver) and 2.5KHz(transmitter) is obtained by dividing the 4.5MHz by 900 times and 1800 times See Table 1 for transmitter/receiver mode VCO frequencies. Program Data PLL IC (IC301) X-TAL (X301) VCO, VARICAP DIODE (D301) IC1301 is CMOS LSI that includes most of

34、 PLL block. The Q301, L301, C311, C312, C313, C314, variable capacitance diode D301 are clapping oscillator circuit to operate as a VCO of the IC301. Q305 is a switching transistor to connect or disconnect the tuning capacitor in the VCO oscillator tank circuit for transmitter or receiver. Q302 work

35、s as a buffer amplifier for RX local frequencies (16MHz) and TX carrier generating frequencies(13MHz) 4-3-2. Reference Frequency The crystal X301(4.5MHz) and other components at Pin 1 and 24 of IC301 can make a reference frequency oscillator with internal amplifier. 4-3-3. VCO Q301 and surrounding p

36、arts are consisting a clapping oscillator works as a VCO of IC301. With appropriate control voltage on D301 the VCO can be oscillate over the required range of 13.4825MHz to 16.710MHz. 4-3-4. Programmable Divider and its Control The programmable input for each channel are stetted by the PLL Clock(Pi

37、n 11), PLL Data(Pin 12), PLL Enable(Pin 13) of IC801. Each input signal to control the PLL IC is done with provide key input Pin 18, 19, 25, 26, 27, 28, 29, 32, 33, 34, 35, 37. For each key input, an internal code converts EEPROM appropriate control to the programmable divider for that channel. Sinc

38、e the change transmit and receive, and additional bit is required at Pin 8 of IC801 to allow the ROM to recognize the status TX or RX. During transmit the push to talk switch makes Pin 8 ground with BRT(Q802), PLL IC works under transmit status. The programmable divider output fed to the phase detec

39、tor for compare with the 2,5KHz reference frequency IC301. See table 1 for actual input and divide ratio on all channels. 4-3-5. Phase Detector and VCO Control The phase detector is a digital phase comparator witch compares the phase of the reference signal with programmable divider output square wa

40、ves and develops a series of pulses whose dc level depends on the phase error of each signal. The phase detector pulse output is fed to an active low pass filter and RC low pass filter output signal of IC301 is filtered and fed to varicap D301 control the VCO frequency. 4-3-6. Transmitter / Receiver

41、 Buffer AMP Output signal of Q301 is fed into the buffer amplifier Q302, L302 to generate TX carrier frequency and 1st local frequencies. 4-3-7. Transmitter Doublers The output signal of Q302, L302 goes to an amplifier with tuning circuit Q701, L701, L702 which doubles incoming 13MHz signals. 4-3-8.

42、 Switching of Turning Capacitor in VCO The VCO circuit must tune with a wide range of frequencies 13.4825MHz 13.7025MHz for transmitter and 16.27MHz 16.71MHz for receiver. To comply above range of VCO, the tuning capacitance should switch for transmission. The tuning circuit consists with L301, C311

43、, C312, C313, and C314. When the VCO is working as a receiver Q305 becomes turn OFF. So, L301 and C311, D301 makes turning function. When transmitting, Q305 becomes ON. S the o, L301 an parallel capacitance of C316 and C311 make turning function. 4-3-9. Receiver Local Oscillator Outputs ? FIRST MIXE

44、R : The secondary output signal of L107 is injected to the sources of 1st mixer Q102, Q103 in the 1st IF mixer section. ? SECOND MIXER : The output of 10.24MHz oscillator circuit with X101 is injected into the IF IC(IC101) internally. Incoming IF signal and 10.24MHz signal are mixed inside the IF IC

45、 to extract 2nd IF signal 455KHz. FM audio Signals are recovered with the way of quadrature detector. AM signals are recovered with envelope detector. 4-4. Frequency Stability Let : Fo = Crystal oscillator frequency Fr = Phase detector reference frequency Fvco = VCO frequency Ft = Transmit frequency Then : Receiver : Fr = Fo/900 Transmitter : Fr = Fo/1800 And under locked conditions : Fr = Fvco / N Where, “N” is the programmable divider divide ratio. Then : Fvco = N X Fr) From which it can be seen, the percentage error in Ft is the same as the percentage error in Fo. The stability of t