Ericsson GE MASTR II 19A149979P1 Maintenance Manual Download Page 6

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DESCRIPTION

The ERICSSON GE MASTR

II Base Station 12/24

Volt Power Supply provides up to 429 watts to power a
MASTR II 800 or 900 MHz base station receiver, system
circuitry, and transmitter. The nominal 12 volt output is ac-
tually 13.0 Vdc and provides a maximum of 3 amperes to
power the receiver and system circuitry. The nominal 24
volt output is actually 26.0 Vdc and provides a maximum of
15 amperes to power the transmitter power amplifier.

The 60 Hz Model (19A149979P1) operates from a

nominal 121 Vac, 60 Hz source. If a 208/220/240Vac, 60 Hz
source is used, an external step-down transformer (similar
to 19C307148P1) must be used with the ’979P1 supply. The
50 Hz model (19A149979P2) provides the same output as
the ’979P 1 supply, but operates from a nominal 230 Vac, 50
Hz source. The output voltage will change a maximum of +
1.6% for each + 1.0% change in the input line frequency.

The power supply’s step-down ferroresonant trans-

former provides excellent line voltage regulation. For the
rated input line voltage range (

20% for P1,

15% for P2),

the output voltage will not vary more than 2 %. A ferroreso-
nant power supply provides inherently excellent line voltage
surge protection, and fewer parts for high reliability. No ac-
tive semiconductor devices are used which could reduce re-
liability.

The output voltages will vary depending on the load cur-

rents that the supply is being asked to source. As the load
current rises, the output voltage will drop. Typical output
voltages for various load currents are as follows:

The operation and servicing of the power supply are

completely accessible from the front. The ON/OFF switch
and all fuses are located on the front panel. The low profile
slot type fuse holders contain the primary fuse(s) F1 (F1 and
F4 for P2), the high current output fuse F2, and the low cur-
rent output fuse F3. The primary fuse(s) protect the input
wiring to the ferroresonant transformer (one 10 amp fuse for
P1, two 5 amp fuses for P2). The output fuses F2 (20 amps)
and F3 (5 amps) provide external overload protection.

The 60 Hz supply provides a courtesy dual AC recepta-

cle. The primary line current fuse (F1) also provides over-
current protection for the dual receptacle. The 60 Hz supply
draws 5 amps under nominal conditions and 7 amps under
all conditions. Thus, the dual courtesy receptacles are rated
for 3 amps.

CIRCUIT ANALYSIS

In the 60 Hz power supply (’979P 1), the ON/OFF

switch (S1) provides line voltage to the power supply
through the primary line fuse F1. Line current flows through
F1 to the courtesy receptacle prior to S1. This allows line
voltage to always be available at the receptacles. Current
then flows through the primary of stepdown transformer
(T1) via the 200°C thermal fuse. The thermal fuse would
only open in the unlikely event that an internal short would
develop in the transformer. The varistor (VR1- 150 V rat-
ing) provides addition input line voltage suppression.

In the 50 Hz power supply (’979P2), the ON/OFF

switch (S1) is a DPST type switching both primary AC
lines. In addition, both input lines have 5 amp fuses (F1 and
F4). The varistor (VR1-275 V rating) provides additional in-
put line voltage suppression. When power is applied, cur-
rent flows through the primary of step-down transformer
(T1) via the 200°C thermal fuse. As in the 60 Hz model, the
thermal fuse would only open if the transformer develops an
internal short.

The step-down transformer (T1) is a ferroresonant type

which has inherently good input line voltage regulation.
This eliminates the need for additional high current regula-

A ferroresonant power supply is designed to work
specifically at a given frequency. The 60 Hz and 50
Hz supplies should be used at their nominal fre-
quency

2 Hz.

NOTE

LOAD CURRENT CONDITIONS

12 V OUTPUT

24 V OUTPUT

TX AND RX SIMULTANEOUSLY

(15 + 3 AMPS)

~13.0 VDC

~26.0 VDC

RX ONLY

(0 + 3 AMPS)

<15.8 VDC