Service Manual 3. Baseband Section
6
3.1.2 Working Principle
100-240VAC power, after being converted to 13.6VDC in the AC-DC converter, passes
through the power control board and then feeds to the repeater. When AC power is
interrupted, an external lead-acid battery takes over supplying power to the radio. When AC
power recovers normal, the power control board feeds AC power to the repeater and charges
the backup battery at the same time. One line of power through the linear regulator circuit
outputs 9.3V, which is then tuned by LDO regulators, generates 3.3V and 5V to analog
circuits in the RF section. One line of power adjusted by the DCDC provides 5V to the DCDC
and various LDOs. The 1.2V DCDC outputs 1.2V to some modules in the digital circuit and
LDO regulators supply 3.3 V to various modules in the digital circuit. Another line of 5V power
feeds to the front panel via the external interface.
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General