V10/V7.5/V5/V3.5 Installation and Operation Manual
Page
5-3
Section 5 System Level Troubleshooting
Issue 3.5
5.3.1.2 Local Troubleshooting
Local on-air troubleshooting consists of
monitoring the transmitter's diagnostic
display 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
troubleshooting action for a given fault.
5.3.2 Off-Air Troubleshooting
Off-air troubleshooting must be performed
when replacement of a defective RF power
module or routine on-air calibration
adjustments will not restore operation.
Nautel recommends the output be
connected to a precision 50
Ω
resistive
dummy load (rated at a minimum of
15,000 W for V10, 10,000 W for V7.5,
7,500 W for V5, 5,000 W for V3.5) for off-
air troubleshooting procedures. If an
appropriate dummy load is not available,
troubleshooting for a majority of faults can
be performed with the power amplifier
stage turned off. The transmitter may
remain connected to its antenna for these
procedures. The RF output level should be
reduced to a minimal value when the RF
output is connected to the antenna and it is
necessary to troubleshoot faults in the
power amplifier stage.
When the intermediate power amplifier
(IPA) module is defective and a serviceable
replacement is not available, it can be
replaced – while the transmitter is off-air -
by a slightly modified operational RF power
module. In dual IPA module V10/V7.5
transmitters, a defective IPA module may
be removed on-air if the standby IPA
module is operational. In dual IPA PA
V5/V3.5 transmitters, the transmitter will
stay on-air if the standby IPA PA is
operational, but the transmitter must be off-
air to service a defective IPA. See 5.11 for
IPA module replacement instructions.
In the event of a LVPS or fan supply
module failure, station policy will dictate
when to replace the defective module. A
transmitter with an operational standby
LVPS or fan supply module may remain
on-air. Before replacing an LVPS module,
fan supply module or any of the
transmitter’s PWBs, press
RF Off
and
switch off the ac at the service entrance.
Operation can only be restored when the
defective LVPS module, fan supply module
or PWB is replaced.
NOTE
The Repair Manual contains component
level troubleshooting information that may
assist the maintainer when performing off-
air troubleshooting.
5.4 ELECTROSTATIC PROTECTION
The transmitter contains semiconductor
devices that are susceptible to damage
from electrostatic discharge. Prior to
removing an assembly from the transmitter,
and while servicing an assembly, observe
the following precautions:
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. Periods of low
humidity magnify this effect. This high
voltage may damage components such as
ICs, FETs, thyristors, and Schottky diodes
unless adequate precautions are taken.
5.4.1 Discharging of Personnel
Maintainers should be electrically
discharged by a suitable grounding
system (anti-static mats, grounding
straps) during removal of a sub-assembly
from the transmitter and while handling
the sub-assembly for maintenance.
