Alinco DX-70, Service Manual

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3) F ro n t U n it
a. P ow er Switch
b. P o w er Supply
c. Dimmer Circuit
d. LCD
e. Others
stored in IC1004 is reset by the output from CPU.
The dial rotation pulse is charged in D1016, R1022 and C1010, and the average
voltage according to the speed is obtained. When the dial rotation speed is fast,
the frequency step per pulse is four times that at normal speed.
When SW1001 is pressed, Q1001 is turned ON, then the contact of RL602 in PA
unit is turned ON to supply the voltage of 13.8V to the front unit. Once the CPU
starts operation, the output from PCONT of CPU turns Q1006 ON to hold ON the
relay of RL602.
When SW1001 is kept pressing while the power is ON, the signal is detected in
PSDET, and the 01006 is turned OFF to cut OFF the power supply.
1C1007 is the regulated power supply of 5V which has the output for CPU reset.
IC1006 is the regulated power supply of 8V which generates the required voltage
for IF shift and volume control.
When the power supply is cut OFF, the output of regulated power supply of 8V is
increased first, and it is detected in D1018 and IC1002:D, then sent to CPU. In
CPU the data is stored in the EEPROM of IC1005 before the output of regulated
power supply of 5V is decreased and the unit is reset. D1019 and C1002 are used
to hold the output voltage of 5V by keeping the input voltage of 5V regulated power
supply as long as possible.
The regulated power supply ol about 10.5V consists of Q1003, Q1004 and Q1005.
Q1003 supplies about 10.5V when the DIMM output from CPU is 5V.
In CPU unit, DIMM is the pulse output, and it switches ON/OFF of the output of
about 10.5V.
At full lighting the output from CPU is fixed to 5V. In ’'LP4" mode the duty is 80%
and in "LP 3 " mode the duty is 60%. In this way the brightness is changed by the
duty in Q1003.
Q1003 is supplied the current by turning ON/OFF. At the maximum the brightness
is the lightest, and the duty is decreased according to the dimmer, then the power
dissipation is decreased. The dimmer can be operated by the small transistor.
The maximum brightness is 10.5V, and it is set to under the regulation voltage
(5.3V x 2) to prolong the life of the lamp. The rush current when the lamp is turned
ON is in pulse mode to decrease the load on the lamp.
The indication such as frequency that is required the speed is performed by the
CPU itself, and the other indications are performed by the LCD driver of 1C1009.
The LCD indication employs the frame frequency of about 128Hz, 1/2 DUTY and
1/2 bias.
X1001 is the ceramic resonator of 8MHz selected not to enter the amateur band in
the harmonics relations.
When the power is ON, the voltage is supplied from Y2 and Y3, to detect whether