Kenwood TS-990S Service Manual

Also see for SP-990: Instruction manual

Contents

TS-990S35CIRCUIT DESCRIPTION8-8. AGC Voltage Output CircuitThe AGC voltage output (MAGCV) for the main signal re-ception is sent from the TXMRX-DSP to the R channel of theDAC (IC397) at an fs of 96kHz. The signal output from theR channel of the DAC is sent from the MAGCV connector(CN101) to the RX unit (X55-313 A/2 CN28) via the controlunit (X53-452 CN32 and CN72) after passing through thebuffer amplifi er (IC681).The AGC voltage output (SAGCV) for the sub signal re-ception is sent from the SRX-DSP to the L channel of theDAC (IC388) at an fs of 48kHz. The signal output from theL channel of the DAC is sent from the SAGCV connector(CN671) to the TX-RX unit (X57-827 A/2 CN2) after the sig-nal passes through the buffer amplifi er (IC662).Fig. 40 Signal for the band scope and decoder use and the AGC voltage output path8-7. Signal Path for the Band Scope and DecoderUseThe IF signals (MSCPI and SSCPI) for the band scopeuse and decoder use are sent to each DAC from the SRX-DSP.The DAC (IC385) converts the MSCPI signal to an analogsignal at an fs of 48kHz. The signal output from the R chan-nel of the DAC is sent to the control unit (X53-452 CN450)from the MSCPI connector (CN662) after passing throughthe active fi lter (IC669).The DAC (IC385) converts the SSCPI signal to an analogsignal at an fs of 48kHz. The signal output from the R chan-nel of the DAC is sent to the control unit (X53-452 CN451)from the SSCPI connector (CN669) after passing throughthe active fi lter (IC656).9. Control Circuit9-1. OutlineThe control circuit consists of the main MCU (IC46) alongwith the EEPROM (IC47), reset IC (IC44), RTC IC (IC49),extension output ICs (IC31 to IC34, IC36 to IC39, IC42, andIC43), scope MCU (IC380), and scope DSP (IC381).9-2. Main MCU and Its PeripheryThe main MCU (IC46) operates at a power supply volt-age of 3.3V and a clock frequency of 88.4736MHz obtainedby multiplying 11.0592MHz in the main MCU by eight. Fur-thermore, the number of output ports is insufficient. There-fore, 10 expansion ICs are prepared to compensate for 80ports.The 3.3 V power supply must be always supplied. There-fore, this power supply is different from other power supplies.The main MCU is connected with the EEPROM (IC47) forbackup use, clock count RTC IC (IC49), and reset IC (IC44) .The EEPROM mainly stores adjustment data, MAC address,and various set values. In order to suppress the standbypower consumption of the transceiver when the transceiveris turned OFF, a setting (turned ON by default for modelsshipped for European countries) allows the main MCU to gointo stop mode to reduce the standby current.This mode is available to models shipped for countriesother than European countries.The UART mainly performs other MCU communication ata baud rate of 115,200 bps.9-3. Scope MCU and Its PeripheryThe scope MCU (IC380) is powered by a supply voltageof 3.3 V and operated at a clock frequency of 18.432MHzsourced by a crystal oscillator that oscillates at the same fre-quency. The scope MCU is mainly in output timing and resetcontrol of the drawing data of the scope DSP (IC381). Addi-tionally, the scope MCU is in the PLL and DDS control of thescope unit (X42-343 A/10) and the switching of the BPF forIF use.IC300SRX-DSPIC385DACRchIC397DACRchIC388DACL/RIC669(A/2)IC669(B/2)Active LPFCN662MSCPIIC662(B/2)BufferIC656(A/2)IC656(B/2)Active LPFIC681(B/2)BufferCN671SAGCVMAGCVCN101CN669SSCPIIC202TXMRX-DSP