Ericsson 19A149978P1, Maintenance Manual, Page: 7 / 18

load to prevent the output voltage from ever rising above 18
volts under any load condition. Under normal conditions
jumper P802 is installed connecting the bleeder resistor
(SW GND) to A-. In 60 Hz models (Rev. A and earlier),
prior to Rev. B, this is done using a ground strap externally
connected between F801B-2 and F801B-3. When the emer-
gency power option is used, the jumper or ground strap is
removed. This allows the relay K3 in charger 344A3168 to
ground or open the bleeder resistor. When line voltage is
present, the relay grounds the bleeder resistor to A-. In an
emergency power condition, the relay open-circuits the
bleeder resistor preventing premature drainage of the battery
powering the station.
The high current filter sources current to both the high
current and the low current output ports. It can source up to
33 Amps through 40 Amp fuse (F2) to the high current ter-
minal strip (F801B) on the rear wall of the power supply
chassis. F801B-1 and F801B-2 are A + and A-, respectively,
and connect to the transmitter power amplifier. For base sta-
tions that do not have emergency power options, F801B-3
and F801B-4 are not used. For emergency power options,
F801B-3 & 4 provide connection between the power supply
and the charger. In an emergency power condition, the ex-
ternal battery is connected through the charger, and through
the power supply, to provide emergency power for the base
station.
The high current filter sources up to 4 Amps through 5
Amp fuse (F3) to the 9 pin molex connector (J801). This
port provides power to the receiver and system circuitry in
the base station. J801-1,2,3 are A + and J801-4,5,6 are A-.
An internal jumper between J801-7 and -8 allows a feedthru
for the optional emergency power status line. J801-9 pro-
vides SW GND for the emergency power options.
The power supply is rated for a nominal 13.2 Vdc for a
29 Amp load out of F801B and a 4 Amp load out of J801
(receiving and transmitting simultaneously). When receiv-
ing only (a 3 Amp load out of J801), the output voltage is
less than 16.0 Vdc.
MAINTENANCE
For disassembly, remove 8 screws and lift off top cover.
Disassembly is required before working on the power sup-
ply. When replacing any component be certain to use an
identical component. Thermal joint compound is required
between diodes D1, D2 and D3 and the heat sink.
TROUBLE-SHOOTING
The trouble-shooting procedure in Table 1 may be help-
ful in isolating a defective component or assembly in a mal-
functioning power supply. When a component or assembly
is identified as defective, replace the defective component
with an identical component. Be sure to check associated
circuitry for any other damaged components before apply-
ing power to the unit.
ADJUSTMENTS
This power supply has no adjustments or controls other
than the ON/OFF switch.
INSTALLATION
The power supply is normally installed in an EIA 19
inch wide rack of a MII base station cabinet. It can also be
installed in a 19 inch wide stand alone open rack.
Insure that ventilation holes in the unit are not ob-
structed when the unit is mounted or in operation.
NOTE
To avoid electrical shock, disconnect power supply
from the AC input power source before removing or
replacing any component or assembly.
WARNING
LBI-38550
7