Abell A720T Service Manual
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Abell A720T Service Manual

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A720T (VHF) Service Manual V1.0
A720T (VHF) Service Manual
ABELL INDUSTRIES CO., LTD
1/56

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  • Page 1 A720T (VHF) Service Manual V1.0 A720T (VHF) Service Manual ABELL INDUSTRIES CO., LTD 1/56...

  • Page 2: Table Of Contents

    A720T (VHF) Service Manual V1.0 CONTENT CHAPTER 1 INTRODUCTION..............................4 1.1 SCOPE OF APPLICATION...............................4 1.2 SECURITY ISSUES................................4 CHAPTER 2 STRUCTURE AND KEY FUNCTIONS......................5 2.1 STRUCTURE..................................5 CHAPTER 3 COMPOSITE MODE............................7 3.1 MODE....................................7 3.2 HOW TO ENTER EACH MODE............................. 7 3.3 PC MODE.................................... 7 3.3.1 P...
  • Page 3 7.1 THE REQUIRED TEST EQUIPMENT......................... 25 7.2 DEBUGGING INTRODUCTION........................... 27 CHAPTER 8 PARAMETERS..............................32 BILL OF MATERIALS (ELECTRONICS)..........................34 FIG.1 A720T BIT MAP................................49 TOP SIDE：.....................................49 BOT SIDE：.................................... 50 FIG. 2 A720T SCHEMATIC DIAGRAM.......................... 51 FIG. 3 A720T BLOCK DIAGRAM............................ 55 FIG. 4 A720T PACKING..............................56 3/56...

  • Page 4: Chapter 1 Introduction

    Two way radios can produce and emit electromagnetic energy to outside, and electromagnetic transmission safety design of ABELL two way radio completely conforms with national and international standard. In order to ensure the best communication effect of two way radio and the electromagnetic transmission safety for human, when you use two way radios for communication, please keep the two way radio perpendicular to the ground, and your month away from microphone 2.5-5 cm.

  • Page 5: Chapter 2 Structure And Key Functions

    5 Antenna ○ 6 Knob: Channel switch Rotate it from channel 1 to channel 32. (note: there are totally 32 channels in two areas of A720T) ○ 7 Knob: Power on/off and Volume control Clockwise rotate it to turn on the two way radio power, you will hear a sound of "click", then continuously rotate it to...
  • Page 6 A720T (VHF) Service Manual V1.0 adjust volume. When you want to turn off two way radio, counter-clockwise rotate the knob until hear a sound of "click". Note: if you turn off the power on sound when programming, you will not hear the power on sound.Check the battery when power on failure to make sure battery installed properly.

  • Page 7: Chapter 3 Composite Mode

    Through programming software, come into debugging mode. PC mode 3.3.1 Preface Use programming cable to connect A720T and PC, operate programming software (ABELL A720T programming software) on PC to make programming setting for communication equipment. Figure 1 shows the process of programming setting on PC.
  • Page 8 Program on PC  If use PC with ABELL two way radio programming for transmitting data to radio, the setting destination data (basic communication parameters) can all be modified. as the value is automatically generated in setting frequency range(frequency type), generally it is not necessary to change destination data. the value can be changed only in necessary condition.

  • Page 9: Chapter 4 Disassembled Parts In Maintenance Process

    A720T (VHF) Service Manual V1.0 Chapter 4 Disassembled parts in maintenance process 4.1 Disassemble the radio 1. Remove two screws and take away the belt clip 2. Rotate to remove antenna 3. Pull out volume and channel knob 4. Remove waterproof ring 5.

  • Page 10: Explosive View

    A720T (VHF) Service Manual V1.0 4.2 Explosive View 10/56...

  • Page 11: Chapter 5 Unit Circuit

    A720T (VHF) Service Manual V1.0 Chapter 5 unit circuit 5.1 DMR digital circuit Signal block diagram 4FSK digital signal channel process of Block diagram of DMR digital circuit: Via MIC, voice comes into NJM2904V, being amplified; After that DSP digital signal is processed to 4FSK ...

  • Page 12: Receiver

    A720T (VHF) Service Manual V1.0 C F300 450 KHz F50 0 U500 U306 Q 501 D1 D3 B AP6 5-03 AK236 5A TDA28 22 RF AMP 58.05MHz 57.6MHz Q 601 X6 00 19.2MHz U601 Q 601 Q 602 U307 PLL VC O...

  • Page 13: First Frequency Mixer

    A720T (VHF) Service Manual V1.0 5.3.2 First frequency mixer The signal from the RF amplifier is mixed with the first oscillator signal from the PLL frequency synthesizer circuit at the first mixer (Q502) and generates the 1st IF signal of 58.05MHz.The first if signal is further eliminated by a two-stage single-crystal filter (F500).

  • Page 14: Phase Locked Frequency Synthesize

    A720T (VHF) Service Manual V1.0 W/N SW IC501 FM IF IC U500 U306 TDA2822 Q311 IF AMP AK2365A HP F De_emphasis Q302 Power S W U301 TLV320AIC3204 U302 SCT3258 QT /DQT U300 CP U Chart 3 AF Amplifier and Squelch 5.4 Phase Locked Frequency Synthesize...

  • Page 15: Unlocked Detector

    A720T (VHF) Service Manual V1.0 mode), adopt voltage-controlled oscillator to control oscillation frequency. In receiving mode, Q607 conduct to provide Q601 power supply. In transmitting mode, Q607 cut off Q611 to conduct and provide Q602 power supply. (Q607 cut off or conduct is determined by output high/low level of micro processor. Micro processor(U300 and 56...

  • Page 16: Voltage-Controlled Oscillator(Vco) And Rf Amplifier

    A720T (VHF) Service Manual V1.0 5.5.4 Voltage-Controlled Oscillator(VCO) and RF Amplifier Signal comes from VCO buffer amplifier(Q605) will be amplified when through Q606, Q8, and Q10. This amplified signal go through amplifier and Q3(RF MOSFET DOLULE), the RF power will be 5W if you set radio as high power, will be 1.5w if your set radio as low power.

  • Page 17: Power Supply

    A720T (VHF) Service Manual V1.0 5.6 Power Supply J404 input +7.5V to U313 LM2734X to born +3.3V voltage to power U300 micro processor. J404 input+7.5V to U308 XC6204B502MR +5.0V(5C) voltage to power VCO and PLL circuit 从 J404. J404 input +7.5V to U314 XC6204B502MR +5.0V(5R)voltage to power receiving circuit and audio circuit.

  • Page 18: Cpu Control System

    A720T (VHF) Service Manual V1.0 5.7 CPU Control System U300 micro processor clock running on 12.228MHz. U 3 1 7 S -8 0 1 2 2A N MC U 3 1 8 R E S E T R E S E T...

  • Page 19: Charter 6 Functions And Configurations

    A720T (VHF) Service Manual V1.0 Charter 6 Functions and Configurations 6.1 Function Definition and Parameter Configuration 6.1.1 Channel This machine can store up 32 channels in 2 areas. 16 channels in each area. 6.1.2 Scan Press preset scan key to active scan function, radio indicator LED will flash yellow. Once signal detected in any of the channels, indicator LED will long bright green, speaker will open.

  • Page 20: Vox

    A720T (VHF) Service Manual V1.0 Default: Turn on 6.1.4 VOX With voice instead of pressing the PTT key, use voice to control transmission by microphone. 6.1.5 TOT To forbid long time channel occupation and to protect radio from being operated for long time transmitting.
  • Page 21 A720T (VHF) Service Manual V1.0 Wait till the “call tone” is finished(if you turned on “call tone” during programming), then start to speak.  Release PTT key to listen/receive signal.  If there is no speaking withing preset time, your speaking/call is over.

  • Page 22: Low Battery Warning

    A720T (VHF) Service Manual V1.0 Release PTT key to receive. When other radio is speaking, indicator LED bright green.  If you turned on “Channel Free” function when programming, after the caller released PTT key, you will hear a ...

  • Page 23: Configurations

    A720T (VHF) Service Manual V1.0 low battery warning tone every 3 seconds. Warning tone in second stage: When battery voltage is lower than 5.8V±0.1, transmitting will be prohibited and radio give low battery warning tone. When you release PTT key, radio will turn to receive mode, indicator LED flash red.

  • Page 24: Ctcss

    A720T (VHF) Service Manual V1.0 6.2.6 CTCSS Program receive(Rx) and transmit(TX) CTCSS code at channel setting.  You radio(Rx CTCSS pre-programmed) can only receive the signal which carries the same CTCSS code, can  receive any signal(no CTCSS code programmed) with the same TX and Rx frequency.

  • Page 25: Chapter 7 Radio Debugging

    A720T (VHF) Service Manual V1.0 Chapter 7 Radio Debugging 7.1 The required test equipment 1. Stabilized power supply 1)The out power can be adjusted from 5V to 15V, and its current is 3A or even bigger. 2)standard voltage is 7.5V.
  • Page 26 A720T (VHF) Service Manual V1.0 Chart 1 Adjustment Frequency List Frequency VHF 136-174 MHz Channel Tx(MHz) Rx(MHz) CH:0 136．000 136．000 CH:1 147．500 147．500 CH:2 156．000 156．000 CH:3 166．500 166．500 CH:4 174．000 174．000 Chart 2 Adjustment QT List Frequency VHF 136-174 MHz...

  • Page 27: Debugging Introduction

    A720T (VHF) Service Manual V1.0 7.2 Debugging Introduction Chart 3 TX Part measurement Regulation Specificati Test Item Condition Termi equipme Component Method enter low power adjustment BAT1 terminal A720T enable to antenna banning low power digital programming automatically 1. low power...
  • Page 28 A720T (VHF) Service Manual V1.0 ( level 1 automatically detect frequency point data 2 adjustment ( level 9 After debugging, frequency point click confirmation to save 2 adjustment detection data A720T programming Wide band 6.audio frequency power software frequency deviation...
  • Page 29 A720T (VHF) Service Manual V1.0 Antenn terminal JK101 3920 send 4FSK signal to radio,then error Testing JK102 radio send demodulated signal back 2.Receive digital 3920 rate： channels: CH1 Connect to 3920. Adjust dBmw of 3920, 4FSK bit error measuring < 5%...
  • Page 30 A720T (VHF) Service Manual V1.0 A720T programming software QT wide band QT: high, QT frequency frequency middle, low port enter QT adjustment deviation deviation RF:wide band power 750Hz±100Hz adjustment high, middle, debug channel meter enable PTT, adjust CH:2 data frequency...
  • Page 31 A720T (VHF) Service Manual V1.0 signal generator audio voltage Antenna A720T enter SQ open speaker test channel meter programming adjustment Level 5 squelch SQ wide band CH:2(middle port) Terminal software adjust squelch to open open speaker open speaker level 5(SSG:-121dBm)

  • Page 32: Chapter 8 Parameters

    A720T (VHF) Service Manual V1.0 Chapter 8 Parameters General Model A720T Frequency range VHF：136-174MHz Channel capacity Channel spacing 25 kHz/12.5 kHz Working temperature -25°C~＋60 °C Frequency stability ±2.5ppm Working voltage 7.4VDC Antenna impedance 50Ω Microphone impedance 2.2KΩ Li-ion DC7.4V 1800mAh(standard) Battery DC 7.4V 2200mAh (optional)
  • Page 33 A720T (VHF) Service Manual V1.0 Audio distortion ≦5% Frequency stability ±2.5 ppm Max. frequency deviation 25K≦5 kHz 12.5K≦2.5 kHz 33/56...

  • Page 34: Bill Of Materials (Electronics)

    A720T (VHF) Service Manual V1.0 Bill of Materials (electronics) Model+ Frequency: A720T(VHF) Date:2017-8-18 Description (specification + package + Materials Cold Amount Bit No. / application mode Color/ Tolerance, etc.) 151-147321Y1-01 SMD carbon resistor 47K +/-5% 0201 1/20W R538 YAGEO RC0201JR-0747K...
  • Page 35 A720T (VHF) Service Manual V1.0 R300 R335 R339 R351 R354 SMD carbon resistor 1K +/-5% 0402 151-11022211-010 R358 R367 R387 R392 R394 YAGEO RC0402JR-071K R460 R564 R600 R657 SMD carbon resistor 1K5 +/-5% 0402 151-11522211-010 R90 R379 YAGEO RC0402JR-071K5 SMD carbon resistor 1K8 +/-5% 0402...
  • Page 36 A720T (VHF) Service Manual V1.0 YAGEO RC0402FR-07100K R93 R95 R328 R325 R329 SMD carbon resistor 100K +/-5% 0402 151-11042211-010 R373 R376 R469 R501 R513 YAGEO RC0402JR-07100K R514 R542 R645 SMD carbon resistor 120K +/-5% 0402 151-11242211-010 R523 R543 R556 R563...
  • Page 37 A720T (VHF) Service Manual V1.0 SMD ceramic capacitor COG 5P +/-0.1pF 081-10501251-040 C520 C504 0402 50V mu Rata GRM1555C1H5R0B SMD ceramic capacitor COG 6P +/-0.1pF 081-10601251-040 C531 C600 0402 50V mu Rata GRM1555C1H6R0B SMD ceramic capacitor COG 8P +/-0.1pF 081-10801251-040...
  • Page 38 A720T (VHF) Service Manual V1.0 0402 50V mu Rata GRM155R71H222K SMD ceramic capacitor X7R 3300pF +/-10% 081-43327251-040 C671 0402 50V mu Rata GRM155R71H332K SMD ceramic capacitor X7R 4700pF +/-10% 081-44727251-040 C401 C647 0402 50V mu Rata GRM155R71H472K SMD ceramic capacitor X7R 5600pF +/-10%...
  • Page 39 A720T (VHF) Service Manual V1.0 C466 C483 C514 C558 C559 SMD ceramic capacitor X5R 1uF ±10% 0402 081-91057221-070 C568 C583 C675 C695 10V YAGEO CC0402KRX5R6BB105 C433 C436 C380 R422 SMD ceramic capacitor COG 9P +/-0.1pF 081-10901351-040 0603 50V mu Rata GRM1885C1H9R0B C140 SMD ceramic capacitor NPO 9pF +/-0.1pF...
  • Page 40 A720T (VHF) Service Manual V1.0 SMD ceramic capacitor X5R 47uF +/-20% 081-94768521-040 1206 10V mu Rata C330 GRM31CR61A476ME15L Non-wound chip inductor 27nH +/-5% 0402 213-27031101-010 L14 L514 L516 mu Rata LQG15HS27NJ02 Non-wound chip inductor 56nH +/-5% 0402 213-56031101-050 L517 TDK MLK1005S56NJ...
  • Page 41 A720T (VHF) Service Manual V1.0 0466003 Light emitting diode SMD red high light 481-3SURC211-01 0603 19-213SURC/S530-A2/TR8 LED1 EVERLIGHT Light emitting diode SMD green high 481-19217221-010 light0603 19-217/G7C-AN1P2/3T LED2 EVERLIGHT 024-B5819103-240 Diode SMD RSB5819WS SOD-323 RS D301 D307 024-SS372108-090 Diode 1SS372 SOT-323 TOSHIBA...
  • Page 42 A720T (VHF) Service Manual V1.0 SC-75/SOT-416 ON Q316 Q323 Q324 041-3400A112-01 Tube field N channel SMD AO3400A Q404 Q405 SOT-23 ALPHA 041-RFM01115-08 Tube field N channel SMD RFM01U7P SC-62 TOSHIBA 041-RFM07141-08 Tube field N channel RFM07U7X 2-5N1A TOSHIBA 041-B506C118-04 Tube field N channel BB506CFS-TL-H...
  • Page 43 ALPS 1.6N 50C-A720T001-01 battery connector A720T PA+phosphor J404 copper+BeCu black 67Y-A780T001-01 antenna contact clip A780T 0.2t BeCu CN201 Gold-Plated PCB Main Board Six layer blind hole A720T 466-720T1211-V0 VHF V2 MP60LI107919A0 112.9*45.2*1.2T Production tools Software check Part Number Version Machine Burn file name...
  • Page 44 Small back cover A720T PC1414 black 61C-A720T002-011 2PCS Copper nut 50B-A720T001-01 Ear mic cover A720T PC black 507-A720T001-01 PTT Button A720T PC orange border+ middle black 50Y-A720T002-01 PTT support A720T PC black 50Y-A720T003-01 alarm button A720T PC orange 1PCS Steel 67Y-A720T001-011 44/56...
  • Page 45 54D-0A510001-01 screw water proof ring A-510 NBR 70 to fasten housing and degrees black aluminum 541-A720T001-01 silica gel PTT button A720T silica gel 60 degrees black 545-A720T001-01 negative and positive rubber pad A720T silica gel 40 degrees orange 547-A720T001-01 transceiver water proof ring A720T silica gel...
  • Page 46 A720T (VHF) Service Manual V1.0 degrees orange 54C-A720T001-01 Mic water proof pad A720T silica gel 40 degrees black 54Y-A720T001-01 potentiometer water proof ring A720T silica for encoder and potentiometer gel 40 degrees orange 54D-A720T001-01 water proof ring A720T 1.0*0.6 NBR 70...
  • Page 47 A720T (VHF) Service Manual V1.0 741-0A720T01-01 model label A720T silver polyester 34.4*29.6mm 749-000ALL01-01 S/N label silver polyester 22*5mm(round) Auxiliary Materials: FL2-A002 white 703 sealant, Spot Light, for Mic 0.24mL FL2-A002 white 703 sealant, for PTT and function keys 0.34mL FL2-A003 8008 sealant, for inner Mic PCB 0.94mL...
  • Page 48 Belt clip A720T PC2805 Metal Parts: 60A-A720T001-11 belt clip A720T zinc alloy electrophoresis 16.2 black 632-A720T001-01 16.3 belt clip Torsion Spring A720T nickel plating 614-00A82001-01 belt clip Hinge A-82 1.9*23.6 SUS301 16.4 nickel plating optional parts: 821-BL227800-00 Li-ion battery AB-L2278 7.4V 2200mAH...

  • Page 49: Top Side

    A720T (VHF) Service Manual V1.0 Fig.1 A720T BIT Map TOP Side： 49/56...

  • Page 50: Bot Side

    A720T (VHF) Service Manual V1.0 BOT Side： 50/56...
  • Page 51 A720T (VHF) Service Manual V1.0 Fig. 2 A720T Schematic Diagram 51/56...
  • Page 52 A720T (VHF) Service Manual V1.0 52/56...
  • Page 53 A720T (VHF) Service Manual V1.0 53/56...
  • Page 54 A720T (VHF) Service Manual V1.0 54/56...
  • Page 55 A720T (VHF) Service Manual V1.0 Fig. 3 A720T Block Diagram A F C O D T M F / B E E P M U T E 55/56...
  • Page 56 A720T (VHF) Service Manual V1.0 Fig. 4 A720T Packing 56/56...

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