Nautel VX150 User manual

3: TROUBLESHOOTING MANUAL
VX150 TO VX2
FM BROADCASTTRANSMITTER
Document ID: NHB-VX150-VX2-TRB
Version: 0.1
Issue Date: 2020-12-01
Status: Preliminary

VERSION 0.1 2020-12-01 PAGE III
VX150 TO VX2 TROUBLESHOOTING MANUAL
Contact Information
Nautel Limited
10089 Peggy’s Cove Road
Hackett’s Cove, NS Canada B3Z 3J4
Toll Free: +1.877.6NAUTEL (662.8835)
(Canada & USA only) or
Phone: [phone] or
Fax: [phone]
Nautel Inc.
201 Target Industrial Circle
Bangor, Maine USA 04401
Phone: [phone]
Fax: [phone]
Customer Service (24-hour support)
+1.877.628.8353 (Canada & USA only)
+1.902.823.5100 (International)
Email: [email protected]
Web: www.nautel.com
The comparisons and other information provided in this document have
been prepared in good faith based on publicly available information.
For verification of materials, the reader is encouraged to consult the
respective manufacturer's most recent publication on the official
website or through contact with Customer Service.
© Copyright 2020 NAUTEL. All rights reserved.

VX150 TO VX2 TROUBLESHOOTING MANUAL TABLE OF CONTENTS
VERSION 0.1 2020-12-01 PAGE 3.V
CONTENTS
Contact Information 3.iii
Responding to alarms 3.1.1
Corrective Maintenance 3.1.1
Electrostatic Protection 3.1.3
Identifying and Troubleshooting an Alarm 3.1.4
Replacement Procedures 3.1.17
Pre-Amplifier/IPA PWB Replacement 3.1.18
Power Amplifier PWB Replacement 3.1.20
Power Supply Module Replacement 3.1.23
Parts Information 3.2.1
Family Tree 3.2.1
How to Locate Information About a Specific Part 3.2.1
Column Content 3.2.2
Reading Electrical Schematics 3.3.1
Component Values 3.3.1
Graphic and Logic Symbols 3.3.1
Reference Designations 3.3.1
Unique Symbols 3.3.2
Identifying Schematic Diagrams 3.3.2
Structure of Schematics 3.3.3
Locating Schematic Diagram(s) for a Functional Block 3.3.3
Locating a Part or Assembly on a Schematic 3.3.4

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Mechanical Drawings 3.4.1
Identifying Mechanical Drawings 3.4.1
Content of Mechanical Drawings 3.4.1
Locating a Part or Assembly on a Mechanical Drawing 3.4.1
List of terms 3.5.1

VX150 TO VX2 TROUBLESHOOTING MANUAL
VERSION 0.1 2020-12-01 PAGE VII
RELEASE CONTROL RECORD
ISSUE DATE REASON
0.1 2020-12-01 Preliminary release for VX150 to VX2. Supports hardware
versions:
VX150, VX300, VX600 (NARF81)
VX1 (NARF79)
VX1.5. VX2 (NARF80)
Supports software version VX SW 1.0 and later.

VX150 TO VX2 TROUBLESHOOTING MANUAL
PAGE 3.VIII VERSION 0.1 2020-12-01

VX150 TO VX2 TROUBLESHOOTING MANUAL RESPONDING TO ALARMS
VERSION 0.1 2020-12-01 PAGE 3.1.1
SECTION 3.1: RESPONDING TO ALARMS
This section provides instructions you need when performing troubleshooting on the VX150 to VX2
transmitter. This section includes the following topics:
Corrective Maintenance
Electrostatic Protection - see page 3.1.3
Identifying and Troubleshooting an Alarm - see page 3.1.4
Replacement Procedures - see page 3.1.17
If none of the procedures and alarms described in this section address your problem, contact Nautel for
assistance. See “Technical Support” in the Installation Manual.
Corrective Maintenance
Corrective maintenance procedures consist of identifying and correcting defects or deficiencies that
arise during transmitter operation. Local and/or remote alarm signals are generated when a
malfunction occurs. If an alarm condition is caused by a malfunction in the RF power stage, the
transmitter may maintain operation at a reduced RF output level. The nature of the fault – and station
policy – will dictate whether an immediate maintenance response is necessary. Fault analysis and
rectification may be conducted from three different levels, with a different technical competence level
required for each: on-air troubleshooting, remote or local, and off-air troubleshooting.
On-Air Troubleshooting
On-air troubleshooting can be performed from a remote location, or locally at the transmitter site.
Remote Troubleshooting
Remote on-air troubleshooting consists of monitoring the transmitter's radiated signal using an on-air
monitor or via a LAN connection, and observing the status of each remote fault alarm indicator.
Information obtained from these sources should enable an operator to decide whether an alarm
response may be deferred to a more convenient time, an immediate corrective action must be taken, or
CAUTION! The transmitter contains many solid state devices that may be damaged
if subjected to excessive heat or high voltage transients. Take every effort to ensure
that circuits are not overdriven or disconnected from their loads while turned on.

VX150 TO VX2 TROUBLESHOOTING MANUAL RESPONDING TO ALARMS
PAGE 3.1.2 VERSION 0.1 2020-12-01
if a 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 “Identifying and Troubleshooting an Alarm” on page 3.1.4 to determine the remedial
action required for a given fault.
Local Troubleshooting
Local on-air troubleshooting consists of monitoring the transmitter's integral meters and fault alarm
indicators. Analysis of this data will normally identify the type of fault, and in most cases will determine
what corrective action must be taken. Refer to “Identifying and Troubleshooting an Alarm” on page 3.1.4
to determine the remedial action required for a given fault.
Off-Air Troubleshooting
Off-air troubleshooting must be performed when routine on-air calibration adjustments will not restore
operation.
It is recommended that the transmitter’s output be connected to a precision 50 resistive dummy load
(rated for at least the maximum transmitter power rating) before starting off-air troubleshooting
procedures. If an appropriate dummy load is not available, troubleshooting 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.
NOTE: Reduce the RF output level to a minimal value when troubleshooting faults in the power
amplifier stage while the transmitter’s RF output is connected to the antenna system .

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VERSION 0.1 2020-12-01 PAGE 3.1.3
Electrostatic Protection
The transmitter's assemblies contain semiconductor devices that are susceptible to damage from
electrostatic discharge. The following precautions must be observed when handling an assembly which
contains these devices.
Electrical Discharging of Personnel
Personnel should be electrically discharged by a suitable grounding system (e.g., anti-static mats,
grounding straps) when removing an assembly from the transmitter, and while handling the assembly
for maintenance procedures.
Handling/Storage
An assembly should be placed in an anti-static bag when it is not installed in a host transmitter, or
when it is not undergoing maintenance. Electronic components should be stored in anti-static
materials.
Tools/Test Equipment
Testing and maintenance equipment – including soldering and unsoldering tools – should be suitable
(i.e., grounded tip) for contact with static sensitive semiconductor devices.
Stress Current Protection
Every precaution should be taken to ensure the static sensitive semiconductor devices are protected
from unnecessary stress current. This is achieved by ensuring that current is not flowing when an
electrical connection is broken, and that voltages are not present on external control/monitoring circuits
when they are connected.
CAUTION! 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. Semiconductor devices such as
integrated circuits, field-effect transistors, thyristors and Schottky diodes may be
damaged by this high voltage unless adequate precautions are taken.

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PAGE 3.1.4 VERSION 0.1 2020-12-01
Identifying and Troubleshooting an Alarm
You can identify an alarm locally by viewing the front panel user interface (UI) (see “Front Panel Alarm
Checks”) or remotely by viewing the remote AUI’s Alarms page (see “Remote AUI Alarms Page Checks”
on page 3.1.7).
Front Panel Alarm Checks
There two ways to check for alarms on the front panel:
Fault LED
Alarms Screen
Fault LED
See Figure 3.1.1. The FAULT LED on the right-hand side of the display indicates that a fault is present.
The FAULT LED will be either off or red. When illuminated, the transmitter has encountered a summary
fault. Use the remote AUI or local UI to view the status of the transmitter.
Figure 3.1.1: Transmitter Front Panel (VX1 shown for reference)
When a fault is present, the transmitter may still produce an RF output. In this case, or if the transmitter
has shut down, you should schedule and commence more in-depth fault diagnosis. See “Alarms Screen”
on page 3.1.5.
FAULT LED

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VERSION 0.1 2020-12-01 PAGE 3.1.5
Alarms Screen
If an alarm exists and is currently being recognized by the transmitter system, it is displayed in the
Alarms screen (Dashboard -> Alarms) of the front panel display (see Figure 3.1.2).
Figure 3.1.2: Alarms Screen
Table 3.1.1 on page 3.1.9 contains a column for most alarms that can occur, sorted alpha-numerically.
The Description and Troubleshooting Action column provides a brief description of the alarm,
troubleshooting tips and a cross-reference to more troubleshooting, if applicable.
1. Scroll through the Alarms screen to view the active faults.
2. Attempt to clear any latching alarms by pressing the Reset Latched Alarms button in the Main
Dashboard -> Alarms screen. If the alarm persists, it will not clear from the display.
3. Locate the alarm name in Table 3.1.1 on page 3.1.9 to determine the cause of the alarm and
perform any recommended procedures in the Description and Troubleshooting Action column.
This may also lead to replacing a suspect PWB, power supply or fan, as detailed in “Replacement
Procedures” on page 3.1.17.
NOTE: Before undertaking any troubleshooting, record all meter readings and note if any other alarms
are displayed on the Alarms screen. record all alarms.
NOTE: Table 3.1.1 on page 3.1.9 contains a column for most alarms that can occur, sorted alpha-
numerically, including both the names displayed on the front panel and, if different, the remote AUI.
The Description and Troubleshooting Action column provides a description of the alarm,
troubleshooting tips, and a link to detailed troubleshooting, as applicable.
4. If troubleshooting and subsequent replacement of a suspect PWB or module causes the alarm to
disappear from the Alarms screen, the alarm has been successfully cleared. If the fault condition
does not clear, contact Nautel.
RESET LATCHED ALARMS

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Remote AUI Alarms Page Checks
If an alarm exists and is being recognized by the transmitter, it is displayed on the Alarms page (see
Figure 3.1.3). The warning symbol in the upper, right section of the remote AUI dashboard (any page)
will be amber or red when an alarm is present.
Figure 3.1.3: AUI Alarms Page
1. Click the warning symbol (or select Menu -> Alarms) to go to the Alarms page (see Figure 3.1.3).
View the list of active faults. Alarms are listed by their name (Alarm column), and then by severity
(Alarm Detail column) [single orange ! indicates low severity (RF output not affected); single red !
indicates medium severity (RF output is reduced); two red ! indicates high severity (RF output is
inhibited)].
2. Attempt to clear any latching alarms by pressing the Reset Latched Alarms button on the bottom
banner of the page. If the alarm persists, it will not be cleared from the display.
3. Locate the alarm name in Table 3.1.1 on page 3.1.9 to determine the cause of the alarm and
perform any recommended procedures in the Description and Troubleshooting Action column.
This may also lead to replacing a suspect PWB, power supply or fan, as detailed in “Replacement
Procedures” on page 3.1.17.

VX150 TO VX2 TROUBLESHOOTING MANUAL RESPONDING TO ALARMS
VERSION 0.1 2020-12-01 PAGE 3.1.7
NOTE: Table 3.1.1 on page 3.1.9
contains a column for most alarms that can occur, sorted
alphanumerically for each sub-system, including both the names displayed on the remote AUI and, if
different, the front panel display. The Description and TroubleshootingAction column provides a brief
description of the alarm, troubleshooting tips and a cross-reference to more detailed troubleshooting,
as applicable .
4. If troubleshooting and subsequent replacement of a suspect PWB or module causes the alarm to
disappear from the Alarms page, the alarm has been successfully cleared. If the fault condition
does not clear, contact Nautel.
NOTE: Before undertaking any troubleshooting, record all remote AUI meter readings and note if any
other alarms are displayed on the Alarms page. Record all alarms. The most convenient way to do this
is by using the remote AUI’s Menu -> Reports page to download a report of the Alarm History (see
“Alarm History” in the Operations & Maintenance Manual). Another method is to use a web browser
over a LAN connection to save screen shots of critical status, meter and alarm pages. Go to the
Dashboard -> Meters page to view (and save) detailed information (see “Viewing Meters” in the
Operations & Maintenance Manual).

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Table 3.1.1: Troubleshooting Alarms
Alarm Name Description and Troubleshooting Action
Analog Audio PWB +12V
Fail
This alarm occurs if the +12 V supply in the analog audio PWB is 10% lower or 10% higher
than the desired value. Check the output voltage of the 12 V power supply module (U2). If
necessary, replace the 12 V power supply module (see ????). There may also be a problem
with the controller’s power supply PWB.
Analog Audio PWB DC
Voltage Fail
Analog Audio PWB Fail/
Missing
Analog Left Audio Low This alarm indicates the analog left audio input level is too low or is not applied. The
transmitter takes no action on this alarm.
Analog Right Audio Low This alarm indicates the analog right audio input level is too low or is not applied. The
transmitter takes no action on this alarm.
Audio Changeover This alarm occurs if the main audio source has been lost, and the exciter has switched to the
backup source as configured by the user.
Audio Player Digital Low This alarms occurs if the audio player is in use on the SBC, but no digital audio is detected by
the controller.
Audio Processor Offline This alarm occurs if the transmitter is configured to include an Orban Inside audio processor,
but it is not communicating with the processor on the internal serial bus. Check all
connections to the Orban Inside audio processor card
Audio Processor Output
Fail
This alarm occurs if the transmitter is configured to include an Orban Inside audio processor,
but it is not detecting audio from the processor. Check all connections to the Orban Inside
audio processor card.
Composite 1 Low This alarm indicates the composite 1 audio input level is too low. The transmitter takes no
action on this alarm.
Composite 2 Low This alarm indicates the composite 2 audio input level is too low. The transmitter takes no
action on this alarm.
Configuration File Not
Found
This alarm occurs when the controller does not find a valid configuration file to load at
power-up. This alarm is unlikely and may clear when the correct settings are entered.
Delaying Turn On This alarm occurs, if the turn-on delay function is enabled, and transmitter is not permitted
turn-on until the delay period elapses. The turn-on delay function is enabled upon an ac
power failure and is typically used to add delay for use with an external generator.
Digital AES 1 Audio Low This alarm indicates the digital AES 1 audio input level is too low. Suspect a problem with the
external audio processor or studio feed. The transmitter takes no action on this alarm.
Digital AES 2 Audio Low This alarm indicates the digital AES 1 audio input level is too low. Suspect a problem with the
external audio processor or studio feed. The transmitter takes no action on this alarm.

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VERSION 0.1 2020-12-01 PAGE 3.1.9
Entered Firmware Upgrade This alarm occurs when the exciter is in “firmware upgrade” mode. It should only be
displayed during a transmitter software upgrade.
Exciter +12V Fail This alarm occurs if the +12 V supply in the exciter PWB is 10% lower or 10% higher than
the desired value. Check the output voltage of the 12 V power supply module (U2). If
necessary, replace the 12 V power supply module (see ????). There may also be a problem
with the controller’s power supply PWB.
Exciter Audio Reset
Exciter DC Voltage Fail
Exciter Failure
External Interlock This alarm occurs when the external interlock input wired to the EXT INTLK terminal is open.
The transmitter will not be able to enable its RF output. Check the interlock connection on
the rear of the transmitter. If the interlock connection is intact, check that all external
interlock switches are closed. If no problem is found with the connection at the transmitter or
any of the external interlock switches, suspect a problem with the interlock circuitry on the
exciter/control PWB (A1).
Fan1/2 Fail This alarm occurs if the speed of cooling fan 1 is below 3000 RPM (half of its nominal value
of 6000 RPM). If either fan 1 or 2 fail, the transmitter takes no action (no effect on the RF
output). If the alarm occurs for fans 1 or 2, check the connection between the indicated fan
and the PS Distribution PWB (A2). If these connections look OK, replace the indicated fan
(see “Cooling fan replacement” on page 1-42). If the alarm still occurs after the fan has been
replaced, suspect the PS distribution PWB.
FPGA Version Mismatch
Forward Power Shutdown This alarm occurs if the transmitter tries to reduce the forward power below minimum (?? W)
due to repeated Forward Power Limiting alarms. The transmitter latches off. See Forward
Power Limiting for troubleshooting tips
Front Panel User Interface
Failure
This alarm occurs if there is a fault with the front panel user interface (UI), preventing it from
being used to control the transmitter. The transmitter will automatically switch to remote
control mode to allow use of the AUI or digital I/O.
High Ambient Temperature This alarm is indication only and occurs if the transmitter’s ambient temperature exceeds
60°C (140°F). Check the intake air filter or cooling fans.
High PA Temperature This alarm occurs if the power amplifier’s heatsink temperature exceeds 85°C (185°F). This
alarm is most likely caused by excessive ambient temperature, a fan failure or blockage, or
excessive power amplifier dissipation. This alarm will clear when the power
amplifier’s heatsink temperature decreases to 75°C (167°F).
Alarm Name Description and Troubleshooting Action

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High SWR This alarm occurs if the transmitter's average reflected power exceeds the high SWR
threshold (?? W). The transmitter takes no action on this alarm. Inspect the antenna and
transmission line system for damage or de-tuning. If there are no major issues with the
antenna network that would cause an impedance change (icing for example), suspect the
Combiner Interface PWB (see “Combiner Interface PWB Replacement” on page 1-50)output
power probe PWB (A7) (see “Output power probe PWB replacement” on page 1-45).
High SWR Shutdown This alarm occurs if the transmitter tries to reduce the forward power below a level that is
equivalent to a 3:1 VSWR (forward power of ?? W) at the SWR Foldback threshold (reflected
power of ?? W) due to a gradually degrading load match. This alarm causes the transmitter
to latch off. Inspect the antenna and transmission line system for damage or de-tuning. If
there are no major issues with the antenna network that would cause an impedance change
(icing for example), suspect the Combiner Interface PWB (A12) (see “Combiner Interface
PWB Replacement” on page 1-50.
Host Not Booted This alarm indicates that the controller’s host has not finished booting. The remote AUI will
not yet be available. Occurrence of this alarm is normal for approximately one to five minutes
while the host is booting, immediately after ac power has been applied/restored or after a
software upgrade. If this alarm continues to occur more than 30 minutes after ac power has
been applied to the transmitter, cycle (turn off, then on) the ac power. If the alarm persists
after 30 minutes, replace the Exciter/Control PWB (A1) (see “Exciter/Control PWB
Replacement” on page 1-46).
Host Not Responding This alarm indicates that the microcontroller (host) that runs the remote interfacing
applications is not communicating with the transmitter’s primary microcontroller (DSP). If the
watchdog function is enabled, the DSP will automatically reset the host. If this alarm persists
for more than 10 minutes, try cycling power (off, then on) to the transmitter. If the alarm
persists, replace the Exciter/Control PWB (A1) if necessary (see “Exciter/Control PWB
Replacement” on page 1-46).
IPA Failure This alarm occurs if the IPA Output Low alarm is present and the measured IPA current is
below 225 mA. The transmitter takes no action on this alarm. See IPA Output Low for
troubleshooting tips.
IPA Output High This alarm occurs if the pre-amp/IPA PWB's forward power is greater than the IPA Output
High threshold (130%/36 W). If this condition persists, replace the pre-amp/IPA PWB (A5)
(see “Pre-amp/IPA PWB replacement” on page 1-42). The transmitter takes no action on this
alarm. If this alarm persists after replacing the pre-amp/IPA PWB, suspect the Combiner
Interface PWB (A12) (see “Combiner Interface PWB Replacement” on page 1-50) or the
Exciter/Control PWB (A1) (see “Exciter/Control PWB Replacement” on page 1-46).
Alarm Name Description and Troubleshooting Action

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IPA Output Low This alarm occurs if the pre-amp/IPA PWB's forward power is less than the IPA Output Low
threshold (70%/14.4 W). This alarm causes the controller to limit the PA voltage to 30 V.
Check for a +48V Supply Fail alarm and follow the associated troubleshooting procedure if
present. IPA Fail and Pre-amp Fail alarms may also be present. If no associated alarms are
present, turn RF off and run the bias routine in the front panel’s Main Menu -> System
Settings -> Calibration menu. If the alarm persists, enable RF and use a digital multimeter to
measure the voltage between pad B on Pre-amp/IPA PWB (pre-amp bias) and chassis
(ground) and also between pad C on Pre-amp/IPA PWB (IPA bias) and chassis (ground). If the
voltage is less than 1 V at either of these points, suspect the Exciter/Control PWB (A1). If the
voltage is greater than 1 V at both of these points, use a digital multimeter to measure
between pad E (IPA volts) on the Pre-amp IPA PWB and chassis (ground). If the measured
voltage is not within an acceptable range (between +43 V and +48 V), with ac power off,
perform a continuity check across F1 of the PS Distribution PWB (A2). If the measurement is
greater than 1 W, replace the fuse (Nautel Part # FA57 in the ancillary kit). If the
measurement is less than 1 W, or replacing the fuse does not clear the alarm, replace the
Pre-amp/IPA PWB (A5) (see “Pre-amp/IPA PWB replacement” on page 1-42). If the voltage
on pad E is acceptable, use a digital multimeter to measure between pad D (pre-amp volts)
on the Pre-amp IPA PWB and chassis (ground). If the measured voltage is not within an
acceptable range (between +43 V and +48 V), replace the Pre-amp/IPA PWB (A5) (see “Pre-
amp/IPA PWB replacement” on page 1-42). If the voltage is acceptable, or replacing the pre-
amp/IPA PWB does not clear the alarm condition, suspect the Combiner Interface PWB (A12)
(see “Combiner Interface PWB Replacement” on page 1-50) or the Exciter/Control PWB (A1)
(see “Exciter/Control PWB Replacement” on page 1-46).
Low Forward Power This alarm occurs if the transmitter's average forward power falls below the low forward
power threshold (defaulted to 50% of the preset power level and is user adjustable) due to
PA failures, fan failures, SWR foldback or a pre-amp/IPA failure. The transmitter takes no
action on this alarm. Check for associated alarms, and follow the associated troubleshooting
procedure if present. If no other alarms are being indicated, with RF turned on, use a digital
multimeter to measure the voltage between pad V and pad W on any PA. If the voltage does
not fall within an acceptable range (between 2.3 V and 3 V), suspect the Exciter/Control PWB
(A1). If the voltage is within this range, perform the “PA resistance checks” on page 1-37,
else suspect the Output Power Probe PWB (A7) (see “Output power probe PWB
replacement” on page 1-45).
Missing Preset This alarm indicates that there are no presets programmed into the transmitter. The user will
not be able to enable RF without first programming a preset.
Modulation Loss This alarm, enabled by the user, indicates that the exciter’s audio modulation level is below
the level specified in the audio loss settings of the active preset (see “Mod Loss” on
page 3.2.110 of the Operations & Maintenance Manual to enable/disable this alarm and to
configure the resulting action). Depending on the setting, this alarm could trigger a preset
change, inhibit the RF or have no effect (alarm only). Check the appropriate program input(s)
and the mod loss setting for the preset.
Muted Transmitter Output For internal control only; no troubleshooting action required
Alarm Name Description and Troubleshooting Action

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No External 10 MHz This alarm occurs if frequency locking to an external 10 MHz source is enabled and no
external 10 MHz is detected. The exciter will automatically switch over to the internal
10 MHz reference, and will continue to run. Check the 10 MHz input. If there are no
problems with the 10 MHz signal and connection, suspect the Exciter/Control PWB (A1).
No LAN Connection This alarm occurs if the transmitter is not detecting communication over the LAN connection.
This alarm is typically only visible in the Events Log, since it will not be transmitted when
communication is interrupted.
No One Pulse per Second This alarm occurs if the pilot phase locking to 1 PPS is enabled and the 1 PPS signal is not
present. Check the 1 PPS input. If there are no problems with the 1 PPS signal and
connection, suspect the Exciter/Control PWB (A1).The transmitter takes no action on this
alarm
Overall Summary Not displayed in AUI or UI status. Configurable as a remote output.This alarms occurs if there
are any alarms present. Check for associated alarms, and follow the associated
troubleshooting procedure, if present.
PA Fail Foldback This alarm occurs if the control system determines that the calculated dissipation in any FET
on a PA is above the high dissipation threshold (?? W), or the forward power being asked for
out of an individual PA [calculated as (output power - combiner losses) / number of active
PAs in the system] is above the PA output high threshold (400 W)(850 W for VS2.5 or 900 W
for VS3). The forward power of the transmitter will be limited to a level such that neither of
these thresholds are exceeded. Check for associated alarms. Typically, the assertion of this
alarm is the result of a PA failure or removal, or a high SWR condition. If no other alarms are
being indicated, contact Nautel for further support
PA Fail/PA1 Fail This alarm occurs if the dc input current for the PA (A7), also PA1 for VX1.5/VX2 transmitters)
has fallen below a predetermined threshold (typically less than 50% of the average PA
current of the operational PAs, or below 500 mA, whichever is lower). This may be caused by
a cabling fault on the PA, loss of PA voltage or bias, or a defective FET. The transmitter's
output power will be reduced (see Table 1.3 on page 1-31) and this condition could cause Per
PA Foldback and Reject Foldback alarms. Perform the “PA resistance checks” on page 1-37.
If there is no problem found with the PA, or the alarm still persists after replacing the PA,
suspect the PS Distribution PWB (A2).
PA2 Fail For VX1.5/VX2 transmitters only. This alarm occurs if the dc input current for PA2 (A8) has
fallen below a predetermined threshold (typically less than 50% of the average PA current of
the operational PAs, or below 500 mA, whichever is lower). This may be caused by a cabling
fault on the PA, loss of PA voltage or bias, or a defective FET. The transmitter's output power
will be reduced (see Table 1.3 on page 1-31) and this condition could cause Per PA Foldback
and Reject Foldback alarms. Perform the “PA resistance checks” on page 1-37. If there is no
problem found with the PA, or the alarm still persists after replacing the PA, suspect the PS
Distribution PWB (A2).
Alarm Name Description and Troubleshooting Action