TM-628H Service Manual V03
Contents
1. and controls EEPROM IC501 RX circuit TX circuit control circuit and display circuit as well as data transmission with peripheral equipment EEPROM TCS01 CDCSS CTCSS DTMF IIS A N TXD RXD x102 0 5 2304MHE CH Decode R PIT PSW Fig 4 Control Circuit 5 2 Reset Circuit The reset circuit consists of a reset IC CN813LESA and peripheral circuits When a breakdown occurs due to change of external voltage the CPU would automatically reboot your radio through the reset IC IC901 5 3 Power Control Circuit Power supply of the radio is derived from B D515 and D516 are diodes for over voltage protection The power can be switched on or off via software see the figure below HYT Mobile Radio Fig 5 Power Supply Circuit Vout supplies power for IC601 IC602 and 1C803 which generate 8V 5V and 3 3V voltage respectively to supply the whole circuit 6 Display Circuit Display circuit comprises CPU IC502 LCD LED and other components Application can be operated manually through programmable keys P1 P4 as well as A and Y Channel information is displayed on the 14 segment display HYT Mobile Radio S301 S302 303 5304 IC301 PI P2 P3 P4 perl a PIE HOOK ae eee 305 306 5307 Key SW UP DOWN ON OFF 9 8304MHz X501 LED LED LED 5C LED Za LED LED LED 0302 302 303 and Semiconductor Data 1 Positive voltage regulator TA7805F Power Unit IC6022. HYT Mobile Radio Short Message Message Menu Short Message Remaining Rental Time Inquiry Remaining Time Inquires about the remaining rental time AUX A AUX A AUX A AUX B AUX B AUX B HOOK MONI This option should be selected when palm Hook Check microphone is used This option should be selected when desktop Monitor microphone is used Selector For controlling the volume as well as Knob Selector Knob selecting the channel and zone Circuit Description Frequency Configuration UHF 400MHz 470MHz Receiver Circuit 1C502 BPF Duo D111 Fa The receiver section configuration is shown as Fig 1 It MK D112 The receiver utilizes double conversion superheterodyne The first IF is 49 95MHz and the second IF is 450KHz The first local oscillator signal is supplied by the PLL circuit while the second local oscillator signal 49 5MHz is generated from the frequenc MHz The PLL circuit generates the frequencies required for transmission See Fig 1 Frequency Range VHF 136MHz 174MHz CPU a AFanp 0511 SPEAKER 2 1 RF AMP BPF UL Kno SP MUTE Procost 1402 CF202 Dut SW WIN Fig 1 Receiver Circuit CF203 The circuit consists of front stage BPF RF amplifier Q111 and final stage BPF D110 and D111 The HYT Mobil
3. TA7808S Power Unit IC601 2 EEPROM CAT24C256WI 256K CATALYST CPU Unit 16501 2 1 Pin Function Pin Function Pin No Name 1 0 Function 1 3 AO A2 I Address input 4 GND Ground 5 SDA I O Serial data input output 6 SCL Serial clock input 7 Write Protect Write protect 8 VCC 5V 20
4. e Radio bandpass frequency range varies with the radio models The BPF is used to eliminate unwanted signals and let only wanted signals go to the mixer 2 2 First Mixer Circuit The signal output from RF AMP amp BPF is mixed with the first LO signal from the PLL circuit at the mixer D112 to generate a 49 95MHZ first IF signal Then the first IF signal will feed through a crystal filter IF200 to further remove spurious signals 2 3 IF Amplifier Circuit After amplified at Q113 the first IF signal enters IC102 TA31136FN where it is mixed with the second LO signal 50 4MHz to generate a 450KHz second IF signal Then the second IF signal feeds through a pair of ceramic filters N CF202 W CF203 where unwanted signals are removed Finally the signal goes to the frequency discriminating circuit of IC102 to output audio signal from Pin 9 2 4 Audio Amplifier Circuit The audio signal from IC102 is amplified and filtered at IC402 and then amplified again at IC401 the received signaling is separated and sent to CPU for decoding Then the signal passes through Q406 AF MUTE and enters IC405 for further amplification After the volume is controlled at K301 on the control panel and SP MUTE is controlled at Q511 the signal feeds into IC511 to output audio signal to drive the speaker 2 5 Squelch Control Circuit One flow of the audio signals from 1C102 feeds into 1C102 from Pin8 for amplification filtering and rectification and then a SQL
5. ignal from detector into DC voltage which is then compared with the reference voltage from CPU in 1C104 to output a DC voltage The DC voltage controls gate electrode of 1C101 so as to control the output power 4 PLL Circuit PLL circuit supplies frequency to receive the first LO signal and TX signal The circuit consists of TX 16 HYT Mobile Radio frequency oscillator Q701 RX frequency oscillator Q702 buffer amplifier Q703 RF amplifier Q102 PLL IC IC801 LPF and TX RX VCO switch Q704 Q706 In TX mode 1C502 provides the frequency data to and activates PLL IC Meanwhile Q704 is turned on to activate TX VCO The output signal is amplified by Q703 and Q102 Then PLL IC divides the signal into 2 5KHz 5KHz or 6 25KHz And phase of it is compared with that of reference frequencies 2 5KHz 5KHz or 6 25KHz from the 16 8MHz crystal oscillator The crystal oscillator has operating frequency of 16 8MHz and frequency stability of 2 5ppm The frequency control voltage output from the phase comparator passes through LPF Q802 and Q803 and then is sent to TX VCO In the meantime TX modulation signal is passed to TX VCO for frequency modulation The working principle of RX mode is similar to that of TX mode 16 8MHz Buff AMP Buff AMP SW Fig 3 PLL Circuit 5 Control Circuit The circuit comprises CPU circuit reset circuit and power control circuit 5 1 CPU HYT Mobile Radio IC120 CPU operates at 9 8304MHz
6. level is derived Then the SQL level is sent to CPU IC502 for comparison with the reference level to generate a level which controls AFMUTE and SP MUTE The level controls Q406 and Q511 to open or close the audio channel Transmitter Circuit The transmitter circuit is composed of MIC circuit modulation circuit RF driver final stage power amplifier circuit and APC circuit HYT Mobile Radio Drive AMP Drive AMP Buffer AMP Fig 2 Transmitter Circuit 3 1 MIC and Modulation Circuit The audio signal from MIC is amplified at IC405 and further amplified pre emphasized and encoded at IC 401 It is added with signaling before going to VCO for modulation The DI modulation circuit is composed of 1C407 and peripheral circuits see the figure above The signal goes to the DI modulation circuit via the TXAF_DI port and then goes to the VCO unit The signal amplitude can be adjusted manually via VR802 allowing accurate modulation of DI without any distortion This circuit can serve as input or output port for GPS and encryption promoting the radio functions to be further expanded 3 2 RF Driver and Final stage PA Circuit TX RF signal output from Q703 in the VCO circuit is amplified at Q101 driver PA Q110 and Q109 and final stage PA IC 101 The signal passes through LPF and goes to the antenna for transmission 3 3 APC Circuit The circuit is used to keep output power at a constant preset value In this circuit D101 and D102 convert the s
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