Chapter 7 MTR3000 Power Supply
7.1 Description
The Power Supply is described in this section. A general description, identification of inputs and
outputs, a functional block diagram, and functional theory of operation are provided. The information
provided is sufficient to give service personnel a functional understanding of the module, allowing
maintenance and troubleshooting to the module level. (Refer to "Chapter 14" for detailed removal or
installation procedures for all modules in the base station/repeater.)
The Power Supply has built in power factor correction and includes a connection for battery backup
that also serves as the DC input when the supply is used in DC only input mode.
7.1.1 General Description
The Power Supply accepts an AC or a DC input (AC input = 85 to 264 VAC,
50/60 Hz, DC input = 21.6 to 32 VDC) and generates three output DC voltages to power the base
station/repeater modules: +28.6 VDC, +14.2 VDC and +5.1 VDC.
The Power Supply is a high-frequency switched mode design, all contained in a metal heat-sink,
mounted on the left-hand side of the base station/repeater. The design provides for output over-
voltage/over-current protection.
The AC input connection is made at the rear of the base station/repeater via an IEC-type connector
keyed to accept only high temperature type mating connectors. Also provided is a Battery Backup
connection (see DC mode above). Power supply cooling, when necessary, is provided by an external
fan (located near the middle of the heatsink) which provides forced air across the power supply
heatsink fins.
Note
When used in DC input mode, the 28.6 VDC output equals the DC input within 0–0.5 VDC.
Note
An external 24 V (nominal) battery system is required to support the battery backup feature
so that when the AC power fails, the MTR3000 Base Station/Repeater (BR) can be powered
from a DC battery source if it is connected to the PS. This results in uninterrupted radio
service (for as long as battery power can be provided). As the PS does not have a battery
charging function, when the AC power is restored, an external charger is required to
recharge the battery.
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