Icom IC-2720H Service Manual

Also see for IC-2720H: Step-by-Step Programming Guide Instruction manual Service manual Operating guide

Contents

4 - 9DescriptionThe 13.8V external DC power from the powerconnector.The same voltage as the HV line which is con-trolled by the VCC regulator circuit (MAIN unit;Q2001). When the [POWER] switch is pushed,the CPU outputs control signal to the powerswitch controller (Q2003) to turn the circuit ON.Common 5 V for the CPU converted from the HVline by the 5V regulator circuit (IC2002). The volt-age line is also applied to the CPU when IC-2720H is power OFF.Common 8 V converted from the VCC line at the+8 regulator circuit (IC2003).Common 5 V produced from the 5 V line by the+5 regulator circuit (Q2002, D2048). The outputsignal is applied to the PTT detector (Q2005),mic amplifier (IC2014, Q2028), etc.VHF transmit.8 V produced from the 8V line at the VT8 regula-tor circuit (Q9, Q11).UHF transmit 8V produced from the 8V line at theUT8 regulator circuit (Q10, Q12).VHF and UHF transmit 8 V produced from the 8V line at the VUT8 regulator circuit (Q13, D1).The output voltage is applied to the buffer ampli-fier (Q38), pre-amplifier (Q16) and pre-driver(Q21).Receive 5 V produced from the 5VS line at theL_R5 regulator circuit (Q1000). The output volt-age is applied to the AM detector for left side dis-play (Q1014, Q1017).Receive 5 V produced from the 5VS line at theR_R5 regulator circuit (Q1002). The output volt-age is applied to the AM detector for right sidedisplay (Q1022, Q1025).Receive 5 V produced from the 5VS line at theL_AM5 regulator circuit (Q1006). The output volt-age is applied to the IF amplifier (Q1040) and FMIF IC (IC1001) for left side display.Receive 5 V produced from the 5VS line at theR_AM5 regulator circuit (Q1005). The outputvoltage is applied to the IF amplifier (Q1041) andFM IF IC (IC1004) for right side display.Receive 5 V produced from the 5VS line at theL_R5 regulator circuit (Q1). The output voltage isapplied to the RF amplifier (Q29) for left side dis-play’s 144 MHz bandpass filter.Receive 5 V produced from the 5VS line at theR_R5 regulator circuit (Q2). The output voltage isapplied to the RF amplifier (Q30) for right sidedisplay’s 144 MHz bandpass filter.LineHVVCC5V8V5VSVT8UT8VUT8L_AM5R_AM5L_R5R_R5L140_R5R140_R5DescriptionReceive 5 V produced from the 5VS line at theR_AM5 regulator circuit (Q3). The output voltageis applied to the RF amplifier (Q31) for left sidedisplay’s 220 MHz bandpass filter.Receive 5 V produced from the 5VS line at theL_AM5 regulator circuit (Q4). The output voltageis applied to the RF amplifier (Q32) for right sidedisplay’s 300 MHz bandpass filter.Receive 5 V produced from the 5VS line at theR_R5 regulator circuit (Q5). The output voltage isapplied to the RF amplifier (Q19) for right sidedisplay’s 430 MHz bandpass filter.Receive 5 V produced from the 5VS line at theR_AM5 regulator circuit (Q6). The output voltageis applied to the RF amplifier (Q20) for left sidedisplay’s 430 MHz bandpass filter.Receive 5 V produced from the 5VS line at theL_AM5 regulator circuit (Q8). The output voltageis applied to the RF amplifier (Q18, Q35) for rightside display’s 910 MHz bandpass filter.Common 8 V produced from the 8 V line by the+8 regulator circuit (Q1023). The output voltageis applied to the VCO circuit (RF unit; Q6,D3–D5) and buffer amplifier (RF unit; Q8).Common 5 V converted from the HV line by the+5 regulator circuit (CONTROL unit; IC3). Theoutput voltage is applied to the buffer amplifier(CONTROL unit; Q2) and reset circuit (CON-TROL unit; IC2).LineL220_R5L300_R5R400_R5L400_R5R800_R5L_VCO8CPU5DescriptionCommon 8 V converted from the VCC line at the+8 regulator circuit (MAIN unit; IC2003). The out-put voltage is applied to the filter switch (IC2),loop filter (Q2, Q3, D2) and buffer amplifier (Q8).Common 5 V produced from the 5 V line by the+5 regulator circuit (MAIN unit; Q2002, D2048).The output voltage is applied to the PTT IC (IC1)and regulator circuit (Q9).Common 8 V produced from the 8 V line by the+8 regulator circuit (Q1023). The output voltageis applied to the VCO circuit (RF unit; Q6,D3–D5) and buffer amplifier (RF unit; Q8).Line8V5VSL_VCO84-4-2 MAIN UNIT VOLTAGE LINE MAIN UNIT VOLTAGE LINE–Continued4-4-3 VCO UNIT VOLTAGE LINE