Kenwood NX-5300 Service Manual page 17

2.4.7 Power Supply Circuit
The battery voltage (+B) is provided from battery terminal. The battery voltage passes through the 3.15A fuse (F1), and goes to RF
final amplifier, AVR ICs (IC31, IC82, IC801, IC36, IC63, IC65, IC64), DC/DC converter (IC33), transistor (Q32, Q71 through the 1A
fuse (F2)), and voltage detector IC (IC20). Voltage detector (IC20) watches battery voltage. If the battery voltage is enough higher
than 5.6V, detector outputs High. Then, IC31 (31BU) outputs 3.1V, and IC32 (12BU) outputs 1.2V, and Q31 is turned on.
When the VOL SW is turned on, SB1 becomes high (battery voltage). The DC/DC (IC33) operates if both SB1 and output of detector
are high. IC33 (38M) outputs 3.8V, and A30 (12M) outputs 1.2V. Then, IC34 (18M) and IC37 (18BT) outputs 1.8V. Then, IC80 (30M)
outputs 3.0V, and IC38 (33BT) and IC35 (33M) and IC81 (33OPT) outputs 3.3V. Then, IC39 (33A) outputs 3.3V, and IC82 (50A) out-
puts 5.0V. Then, IC701 (18M_3) outputs 1.8V, and Q71 (53AF) is turned on. Voltage detector (IC704) watches IC33 (38M) output
voltage. If the 38M output voltage is enough higher than 3.5V, detector outputs High. As a result, the MPU/DSP operate.
The SBC signal becomes High after the MPU/DSP operates, and IC61 (33C), IC36 (50C), IC63 (50VCO) and Q32 (SB2) are turned on.
When SD_EN signal becomes High, IC30 (33SD) operates. When 5UC signal becomes High, IC801 (50U) operates. When TXC signal
becomes High, IC65 (50T) operates. IC65 (50T) is turned on in transmit mode.
When RXC signal becomes High, IC64 (50R) operates. IC64 (50R) is turned on in receive mode. Switches are controlled by the MPU/
DSP.
When the VOL SW is turned off /PSW signal becomes Low. After detecting /PSW signal, the MPU/DSP changes SBC signal to Low.
The 50C is fed to IC60 (200C). IC60 (200C) is the DC/DC boost converter. IC60, D60, C64 consist of a voltage quadruple. The 200C
circuit then outputs approximately +20VDC.
(No.RA015<Rev.002>)1-17