RTS DV 2400 Series, Руководство по обслуживанию

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DV-2400
7
CIRCUIT DESCRIPTION
„
D/A Converter
The D/A converter (U505) is used to adjust MO modulation, AF volume, TV voltage, FC reference
voltage, and PC POWER CONTROL voltage level.
Adjustment values are sent from the CPU as serial data. The D/A converter has a resolution of 256 and
the following relationship is valid.
Power Supply Circuit
When the POWER switch on the display unit is pressed, the power port on the display unit which is
connected to CPU port 45 (P32), goes low, then CPU port 23 (P20) goes high, Q103 turns on, SBE SW
(Q100) turns on and power (SBE) is supplied to the radio.
When the DC power supplied to the radio, the voltage regulator IC (U1) supply into the CPU VDD.
During receiving, the CPU port 19 (P24) output "H" level. Q101 and Q108 turn on. and reception circuit
is supplied by 8V power supply (8R).
During transmitting, CPU port 18 (P25) output "H" level. Q102 and Q104 turn on. Transmitting circuit
output 8V power supply (8T). (See Fig. 15.)
U2
5M
CPU
Q100
SW
Q103
SW
U1
AVR
Q101
SW
Q108
SW
Q106
SW
VFM
Q102
SW
Q104
SW
8R
8T
U100
AVR
U101
AVR
8C
8C
P20
P24
P2
5
FB
POWER SW
P32
Fig. 15 Power supply circuit