Nautel XL12, Технические инструкции

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12 000 WATT AM BROADCAST TRANSMITTER
XL12
Page 5-5
01 January 2002
(b) Measure the incoming AC voltage and verify
the power supply transformer is tapped as
tabulated in table 2-2.
(c) If the power supply transformer taps are
correct, switch off AC input voltage and gain
access to the AC/DC power supply section by
opening the rear door.
(d) Confirm there are no short circuits between the
terminals of inductors A23L1/A23L2 and
ground.
(e) Check 3-phase rectifier assemblies for faulty
diodes.
(f) If no faults were found in steps (d) and (e), the
monitoring circuit is suspect. Contact Nautel
for trouble shooting information
5.5.8 LOW VOLTAGE POWER SUPPLY -
RF DRIVE AMP ALARM:
The RF
DRIVE AMP
alarm indicates that the output of the active RF drive
power supply has fallen below a nominal 56 VDC.
The alarm could result from a fault in the RF drive
power supply (A11A4 or A11A5), faulty detection
circuitry on the RF drive power supply, or a fault in
the alarm circuitry on the system control PWB.
Trouble shoot an RF
DRIVE AMP alarm as follows:
(a) An RF drive DC power supply alarm initiates
an automatic changeover to the standby
exciter. To trouble shoot a defective exciter,
set
Exciter Control
switch A1A3S19 to
AUTO
XFR INHIBIT
and select the suspect exciter.
(b) Ensure exciter associated with suspect power
supply is selected. Measure DC voltage at the
power supply output at E3.
- If the voltage is above 56 VDC, measure DC
voltage at Q2 (collector) or J1-1. If 0 VDC,
suspect the alarm circuitry on the system
control PWB.
- If the voltage is below 56VDC, attempt to
increase the power supply's output by adjusting
the
VOLTAGE CONTROL potentiometer (R3).
(c) If the voltage cannot be adjusted, confirm the
following voltages: +15 VDC at J1-4 and +50
VDC at E1.
(d) If the input voltages checked in step (c) are
satisfactory and the output cannot be adjusted
to the required level, the RF drive power supply
should be removed for repair.
5.5.9 LOW VOLTAGE POWER SUPPLY -
BATTERY LOW ALARM:
A
BATTERY
alarm
indicates that the voltage provided by the battery
backup circuitry is low. The fault may be caused by
weak batteries or a fault in the detection or alarm
circuitry on the system control PWB.
Replace the batteries on XBT1 of the system control
PWB (A1A3). If the alarm remains, suspect the
system control PWB circuitry.
NOTE
Batteries should be replaced once a year or as
soon as weak batteries cause the
BATTERY
alarm
to turn on. This helps prevent chemical dripping
from old batteries and to ensure adequate
backup voltage for the system control PWB's
microcontroller when AC power is turned off.
5.5.10 LOW VOLTAGE POWER SUPPLY -
REGULATED VOLTAGE ALARM:
A
REGULATED VOLTAGE
alarm indicates that at least
one of the exciter's low voltage DC power supplies
(+5V, +15V, -5V or -15V) has failed. The alarm
may be caused by a failure of the power supply, a
fault in the detection circuitry on the exciter interface
PWB, or a fault in the alarm circuit on the system
control PWB. Trouble shoot a
REGULATED VOLTAGE
alarm as follows:
(a) The low voltage power supply alarm initiates
an automatic exciter changeover to the standby
exciter. To trouble shoot a defective exciter
circuit, set the
Exciter Control
switch
A1A3S19 to
AUTO XFR INHIBIT
and select the
suspect exciter.
(b) On the system control PWB (A1A3), measure
the following:
- +8V on TP8
- -8V on TP9
- +24V on TP10
- -24V on TP11
- +48V on TP12
These are unregulated DC voltages and will be
proportional to the AC power source for a
given tap setting.