Nautel XL12, Technical Instructions

Page: 99 / 238

12 000 WATT AM BROADCAST TRANSMITTER
XL12
Page 5-2
01 January 2002
5.3.1 ON-AIR TROUBLE SHOOTING:
On-
air trouble shooting can be performed from a remote
location or locally at the transmitter site.
5.3.1.1 Remote Trouble Shooting:
Remote on-
air trouble shooting consists of monitoring the
transmitter's radiated signal using an on-air monitor
and observing status of remote fault alarm indicators.
Information obtained from these sources should
enable an operator to decide if response may be
deferred to a more convenient time, if immediate
corrective action must be taken and/or whether the
standby transmitter must be enabled (if one is
available). It is recommended that the significance
of remote indications and the appropriate responses
be incorporated into a station's standard operating
procedures. Refer to paragraph 5.5 to determine the
remedial action required for a given fault.
5.3.1.2 Local Trouble Shooting:
Local on-air
troubleshooting consists of monitoring the
transmitter's integral meters and fault alarm
indicators. Analysis of their status will normally
identify the type of fault and in most cases will
determine what corrective action must be taken.
Refer to paragraph 5.5 to determine the remedial
action required for a given fault.
5.3.1.2.1
The power amplifier stage contains an
integral modular reserve (IMR) feature. This feature
permits the transmitter to operate at a reduced RF
output level when a malfunction occurs in any of its
power modules. Station operating procedures will
dictate if reduced RF output level is acceptable.
When reduced RF output level can be tolerated,
replacement of the defective RF power module may
be deferred to a more convenient time. A defective
module may be removed from the transmitter for
servicing, while the transmitter is operating at
reduced RF output level, provided removal
instructions detailed in paragraphed 5.6.1 are met.
Refer to paragraph 5.6 for RF power amplifier
module removal/replacement instructions.
5.3.2 OFF-AIR TROUBLE SHOOTING:
Off-air trouble shooting must be performed when
replacement of a defective RF power amplifier
module or routine on-air calibration adjustments will
not restore operation. It is recommended the output
be connected to a precision 50 resistive dummy
load (rated at a minimum of 20kW) for off-air trouble
shooting procedures. If an appropriate dummy load
is not available, trouble- shooting for a majority of
faults can be performed with RF power turned off.
The transmitter may remain connected to its antenna
system for these procedures. It is recommended RF
output be reduced to a minimal value when
connected to the antenna system and it is necessary
to trouble shoot faults in the power amplifier stage.
ELECTROSTATIC PROTECTION
5.4
The transmitter's assemblies contain
semiconductor devices that are susceptible to
damage from electrostatic discharge. Prior to
removing an assembly from the transmitter, and
while servicing an assembly, the precautions
described in paragraph 4.5 must be observed:
NOTE
Electrostatic energy is produced when two
insulating materials are rubbed together. A
person wearing rubber-soled shoes, walking
across a nylon carpet or a waxed floor, can
generate an extremely large electrostatic charge.
This effect is magnified during periods of low
humidity. Components such as integrated
circuits, field-effect transistors, thyristors, and
Schottky diodes may be damaged by this high
voltage unless adequate precautions are taken.
TROUBLE SHOOTING FRONT PANEL
ALARMS
5.5
Trouble shooting front panel alarms assumes
that the transmitter has been operating normally
before the fault condition occurred. An alarm
indicator displays (or flashes) red when a fault
condition exists.
NOTE
Before undertaking any trouble shooting, press
ALARM RECALL
to see if any other alarm has been
registered and record these alarms. Then press
SYSTEM RESET
to try to clear the alarm(s). If the
alarm(s) clears, it may have been false. If not,
trouble shooting is necessary.
If one or more RF power modules indicate front
panel alarms, try resetting the RF power modules
by pressing the front panel's
RESET
switch. If the
alarm does not clear, troubleshooting is
necessary.