Kenwood NXR-1800 Service Manual page 19

2.5.6.5 ADC, DAC circuit
The ADC/DAC circuit consists of an ADC (IC76) and DAC (IC77 and IC78).
The ADC/DAC performs the following processes:
DAC: Conversion of various RF control voltages from digital to analog.
ADC: Conversion of power supply voltage and various temperatures from analog to digital.
2.5.6.6 LAN
This repeater is equipped with a 100Base-TX or 10Base-T LAN interface.
This circuit consists of IC81 and J7. IC81 is an Ethernet PHY and J7 is LAN connector.
Ethernet PHY (LAN PHY: IC81) is controlled by MPU/DSP (IC33), and the MAC address is saved in eMMC (IC520).
2.5.6.7 OLED Display interface circuit
This repeater has a 1.7inch (128 x 32 resolution) OLED display.
The OLED display is controlled from the MPU/DSP (IC33) via the FPGA (IC60) using the SPI interface.
The SPI signal output from the FPGA enters the buffer IC (BUS BUFF: IC602), where waveform shaping is performed and transferred
to the OLED display. CN7 is an interface connector for connecting the flexible cable of the OLED display module.
2.5.6.8 USB
This repeater has a USB host function and supports USB 2.0. This circuit consists of IC33, J9 and IC251.
IC33 is an MPU/DSP equipped with a USB controller function. J9 is a USB-A connector on the front panel.
The USB bus power supply uses the HIGH SIDE switch (High-side SW: IC251) for overcurrent detection.
The USB host feature is for connecting USB headset speaker-microphone, allowing to monitor the received audio or communicate
with the radio in the system.
2.5.6.9 CONTROL I/O interface (D-SUB 25-pin) circuit
The CONTROL I/O works for the interface between the various external equipment and the repeater.
The circuit consists of a CONTROL I/O connector (D-SUB 25-pin J4), level shifter (BUS SW: IC82 and IC83), RS-232C driver (RS232C
DRV: IC84), and DC switch (DC SW: Q451 and Q452).
For more detail information such as the terminal specification and the function, please refer to "2.7.4 CONTROL I/O D-SUB 25-pin
CONNECTOR".
2.5.6.10 Knob
The knob on the front panel is a Rotary encoder type with Push switch, and it is used for the following:
(1) Turn on the power by pressing and holding knob.
(2) Select a menu by turning knob and determine the menu by pressing knob.
2.5.6.11 FAN control circuit
The FAN control circuit consists of a voltage regulator (9.0V AVR: IC3022) and FET (Q3060 and Q3061).
The circuit performs the following processes:
(1) Switching FAN ON and OFF.
(2) Switching between high speed and low speed of FAN rotation speed by controlling PWM.
(3) Detect FAN failure.
They are controlled by FPGA. And the FAN is turned ON, OFF, high speed of FAN rotation speed or low speed of FAN rotation speed
according to temperature.
2.5.7 Power Supply Circuit
[+ B] is directly connected to the final amplifier (FINAL AMP: Q3069), 9.0V AVR (IC3022), and 8.8V DC/DC (IC4100). 8.8V DC/DC
output is supplied to 7.5V AVR (IC3030) and 5.0V AVR (IC4006).
It is also connected to a 10V AVR (IC600) via a DC SW (IC4010) and to a 9.0V AVR (IC4001) and 3.3V, 5.0V DC/DC (IC4000) via a
fuse (F4000).
The output of the 7.5V AVR (IC3030) is controlled by the FPGA (IC60) and supplies 7.5V to the transmitter as [7.5V]. And [5V_2] is
supplied to the transmitter via the 5.0V AVR (IC3029).
Also, the output of the 5.0V AVR (IC4006) supplies to the receive 5V block.
The 9.0V AVR (IC4001) supplies [9V] to the RX VCO block and TX VCO block by turning on the DC SW (Q4006). 9V to the TX VCO
block is controlled by the DC SW (Q4008).
The 3.3V output of 3.3V, 5.0V DC/DC (IC4000) is supplied to the following circuits.
· MPU/DSP (IC33) turned on by DC SW (Q3) via fuse (F1)
· Serial NOR FLASH (IC52)
· eMMC (IC520)
· Ethernet PHY (IC81) turned on by DC SW (Q2) via fuse (F2)
· LAN connector (J7)
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