RADIOBEACON TRANSMITTER
ND500II (125 WATTS) DOUBLE SIDEBAND - NO VOICE
Page 2-2
01 November 2003
2.2.1.3
+15 Volt DC Regulator
: The +15 volt
DC regulator consists of +15 volt DC regulator
device A1U2, thyristor A1Q3 and associated
components. Normally, +24V will be applied to
power MOSFET transistor A1Q2 and regulator
A1U2. The reg15 volt DC output of A1U2
is applied to zener diode A1CR5/resistor A1R7,
smoothing capacitor A1C2 and to connector A1J1-
8/9 and A1J2
−
1 for distribution throughout the
transmitter. Zener diode A1CR5 ensures the output
of the regulator A1J2 does not exceed 16.0V. If the
+15 volt DC regulated output of A1U2 exceeds
16.0V, zener diode A1CR5 will be forward biased
and turn on. A positive voltage will be applied to the
gate of thyristor A1Q3. Thyristor A1Q3 will be
gated on and clamp the +24V line to ground. Fuse
F3 on the 'B+ VDC' line will blow. The transmitter
will shut down.
2.2.1.4
DC Power Source (Battery)
: The DC
power source (battery) circuit consists of relays
A1K1, A1K2, zener diode A1CR6 and associated
components. When using an AC power source,
relays A1K1 and A1K2 will be energized and the
battery VDC
input on A1J1-3 (+) will be inhibited.
If the AC power source falls below the required
limits, protection circuits within the low voltage
supply on/off PWB (A1A1) will cause relay A1K1 to
de-energize. The
battery VDC
input will be applied
through the contacts of relays A1K1 and A1K2 to
shunt resistor A1R2. If the B+ voltage falls below
approximately 20V, relay A1K2 will de-energize..
When the voltage on storage capacitor C1 exceeds
20V, zener diode A1CR6 will be forward biased
through resistors A1A1R24/R25 energizing relay
A1K2. When relay A1K2 energizes, resistor A1R1
will be removed from the circuit and storage
capacitor C1 will continue to charge directly to the
DC power source (battery). The B+ voltage from the
DC power source is applied through resistor A1R2
and connector A1J1-6/14 for distribution throughout
the transmitter.
When relay A1K1 de-energizes, the ground on
battery status
connector on A1J1-15 is removed. A
DC voltage produced through voltage divider
resistors A1A1R8/A1A1R9 is passed through
connector A1A1J1-10,
battery status
connector
A1J1-15 and applied to the battery-alarm lamp on the
front panel. The lamp will turn on.
2.2.1.5
AC Monitoring
: The AC monitoring
circuit, on low voltage power supply on/off PWB
A1A1, consists of transistors A1A1Q2, A1A1Q6,
power MOSFET A1A1Q7,
LOW AC
potentiometer
A1A1R13 and relay A1K1. Under normal operating
conditions, transistor A1Q2 and MOSFET A1A1Q7
are turned on. Relay K1 is energized and the
battery
VDC (+)
input (J1-3) is inhibited. A DC voltage
developed through resistors A1A1R18/ A1A1R19 is
passed through connectors A1A1J1-5, A1J1-16 and
applied to an AC power status lamp on the front
panel. The lamp turns on. Transistor A1A1Q6 and
resistor A1A1R16 provide hysteresis for the AC
monitor circuitry. The transmitter shuts down when
the AC voltage falls 10% below the desired level and
is restored when the AC voltage increases to 5%
below the desired level.
If the AC power falls below the desired limits, the B+
voltage developed across full-wave rectifier diodes
A1A1CR1/A1A1CR2 and voltage divider resistors
A1A1R3 through A1A1R6 will be insufficient to
overcome the breakdown threshold of zener diode
A1A1CR4. Transistor A1A1Q2 will be reversed
biased and turn off. Transistor A1A1Q6 will be
forward biased and turn on. Resistor A1A1R16 will
be grounded through transistor A1A1Q6 and
MOSFET A1A1Q7 will be reversed biased and turn
off. Relay A1K1 will de-energize and the
battery
VDC
(+) input (A1J1-3) will no longer be inhibited.
The transmitter will switch to the DC power source,
if used. The transmitter will switch back to the AC
power source when it returns to normal.
LOW AC
potentiometer A1A1R13 allows adjustment of the AC
monitor threshold.
The
LOW AC INHIBIT
shorting jumper (A1A1E1) is
positioned for the type of power source configuration.
If an AC only power source is used, jumper E1
should be installed in the
AC
position (shorting pins 1
and 2) and apply a ground potential to A1A1J1-8,
inhibiting the 24V/15V power supplies when the AC
voltage falls below the threshold. If a backup DC
source is used, jumper E1 should be installed in the
AC/DC
position (shorting pins 2 and 3). If the AC
power falls too low, transistor A1A1Q5 will have no
effect on the 24V and 15V supplies and switchover to
the backup DC power source is permitted.
