Icom IC-R20 Service Manual - Page 19

4-4 POWER SUPPLY CIRCUITS 4-4-1 LOGIC UNIT VOLTAGE LINES Line Description VCC The voltage is same as connected battery pack. The voltage is supplied to the charge controller (Q32). CPU3V Common 3 V converted from the VCC line or external DC power supply by the +3 regulator (IC8, pins 1 and 5). The output voltage is supplied to the main CPU (IC3), reset IC (IC2), EEPROM (IC1), etc. Common 3 V converted from the CPU3V line by the +3 regulator (Q13 and Q14). The regulator is controlled by the +3SC line from the main CPU +3S (IC3, pin 40). The output voltage is supplied to the electronics volume (IC7), pre-amplifiers (Q12 and Q16), etc. Common 3 V converted from the CPU3V line by the +3 regulator circuit (Q17). The output voltage +3V is supplied to the CI-V interface circuit (IC4, Q3 and Q6), etc. A_R3 Receive 3 V converted from the VCC line or external DC power supply by the +3 regulators (IC9, pins 1 and 5; Q10). The regulator is controlled by the A_R3C line from the main CPU (IC3, pin 67). The output voltage is supplied to the RF unit, etc. B_R3 Receive 3 V converted from the VCC line or external DC power supply by the +3 regulators (IC9, pins 1 and 5; Q15). The regulator is controlled by the B_R3C line from the main CPU (IC3, pin 75). The output voltage is supplied to the RF unit, etc. 4-4-2 REC UNIT VOLTAGE LINES Line Description Common 3 V from the LOGIC unit via the J7, pin 1, and is then supplied to the SUB_3V regulator +3V (Q2). The regulator is controlled by SUB_3C line from the sub CPU (IC2, pin 45). Common 3 V converted from +3V line by the SUB_3V regulator (Q2). The output voltage is SUB_3V supplied to the sub CPU (IC2), memory (IC6), RECORDING IC (IC7), etc. 4-4-2 REC UNIT VOLTAGE LINES Line Description Common 3 V from the LOGIC unit via the J7, pin 1, and is then supplied to the SUB_3V regulator +3V (Q2). The regulator is controlled by SUB_3C line from the sub CPU (IC2, pin 45). Common 3 V converted from +3V line by the SUB_3V regulator (Q2). The output voltage is SUB_3V supplied to the sub CPU (IC2), memory (IC6), RECORDING IC (IC7), etc. 4-4-3 RF UNIT VOLTAGE LINES Line Description A_R3V Receive 3 V line from the LOGIC unit via the J1, pin 37. The voltage is supplied to the RF (IC19), IF (Q5) and LO (Q540) amplifiers, 1st (IC1) and 2nd (IC10) mixers, regulators, etc. B_R3V Receive 3 V line from the LOGIC unit via the J1, pin 22. The voltage is supplied to the RF (IC18), IF (Q542) and LO (Q555) amplifiers, 1st (IC15) and 2nd (IC16) mixers, regulators, etc. HF3V Receive 3 V converted from the A_R3V line by the +3 regulator (Q509). The regulator is controlled by the HFC line from the main CPU (LOGIC unit; IC3, pin 46). NB3V Common 3 V converted from the A_R3V line by the +3 regulator (Q527). The regulator is controlled by the NBC line from the D/A converter (IC22, pin 13). Receive 3 V converted from the A_R3V line by the +3 regulator (Q501). The regulator is con300M3V trolled by the A_300MC line from the expander IC (IC14, pin 3). Receive 3 V converted from the A_R3V line by the +3 regulator (Q502). The regulator is conA_VHF3V trolled by the A_VHFC line from the expander IC (IC14, pin 2). Receive 3 V converted from the A_R3V line by the +3 regulator (Q502). The regulator is conA_UHF3V trolled by the A_UHFC line from the expander IC (IC14, pin 4). Receive 3 V converted from the B_R3V line by the +3 regulator (Q554). The regulator is conB_VHF3V trolled by the B_VHFC line from the expander IC (IC20, pin 2). Receive 3 V converted from the B_R3V line by the +3 regulator (Q554). The regulator is conB_UHF3V trolled by the B_UHFC line from the expander IC (IC20, pin 3). B_G3V Receive 3 V converted from the B_R3V line by the +3 regulator (Q503). The regulator is controlled by the B_GC line from the expander IC (IC20, pin 4). Receive 3 V converted from the B_R3V line by the +3 regulator (Q503). The regulator is conB_800M3V trolled by the B_800MC line from the expander IC (IC20, pin 5). Receive 3 V converted from the B_R3V line by the +3 regulator (Q546). The regulator is conB_AM3V trolled by the B_AMC line from the expander IC (IC20, pin 18). 4 - 11