Motorola BLE*/* - Manual (Page 17)

2-6 Overview
BLE*/* Installation and Operation Manual
Power Supply
The BLE*/* power supply is a separate circuit board mounted to the underside of the amplifier
module and is capable of 60 Vac or 90 Vac powering. The power supply provides a regulated
24 Vdc output over an ac input between 38 Vrms and 90 Vrms with a line frequency from 50 Hz
through 60 Hz. Potentiometer R25 adjusts the output voltage to 24 Vdc, however, this is set at
the factory and field adjustment is not recommended.
Figure 2-6 illustrates the components on the power supply:
Figure 2-6
BLE*/* power supply
P2-3
P2-2
W1
P2-1
C2
4
C25
C26 C2
L2
C7 C6 C5
L1
C3
D6 D5
D7
U1
T1
C12
U2
C10 J1
LO
HI
C1
C22
R25 C11
U4
U3
L3
C17
Q1
X2
R1
6
E1
E2
D8
SURGE PROTECTOR
X1
D1
L8
P1
1
R25
Surge protector
or FTEC
LO/HI
selector
The power supply also contains a two-position LO / HI selector that sets the start-up voltage for
38 Vac or 55 Vac. The BLE*/* is shipped with the selector in the LO position which is the
standard configuration. The selector should be switched to the HI position only for a 90 Vac
system. This sets the start-up voltage at 55 Vac. Because this is only 5 V below 60 Vac, it is not
practical in a 60 Vac system. There is no damage to the amplifier if the selector is not changed
from the standard
LO setting. However, changing the selector ensures that the dc supply does
not turn on until the proper input voltage, 38 Vac or 55 Vac, is reached. This prevents excessive
loading of the system power supply during turn-on after a system shutdown.
You must remove the power supply cover to access the selector illustrated in Figure 2-6.
Section 3, “Amplifier Setup” explains changing the setting of this selector to meet system
requirements.
The power supply includes a heavy-duty gas discharge tube that you can replace with the
optional fast-transfer electronic-crowbar (FTEC) surge protector. The FTEC is a crowbar circuit
that fires at approximately 245 V and presents a short circuit to the line during periods of
overvoltage. After the ac input voltage returns to normal, the FTEC resumes its open state.
The factory-installed 20-ampere fuse, illustrated in Figure 2-8, provides power-passing to
additional line extenders.