Nautel FM10, Технические инструкции

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10 000 WATT FM BROADCAST TRANSMITTER
FM10
Page 5-19
01 October 2002
TROUBLE SHOOTING FRONT PANEL
ALARMS
5.11
The trouble shooting of front panel alarms
assumes that the transmitter has been operating
successfully before the alarm condition occurred.
The information in table 5-5 is keyed to illuminated
front panel alarm (red) lamps. Locate the offending
alarm lamp(s) and probable cause(s) in table 5-5 and
then refer to the appropriate trouble shooting
paragraph.
NOTE
Ensure alarm indications cannot be reset before
trouble shooting. If the transmitter is latched off
due to IPA SWR or reflected power alarms, press
the
PROTECT RESET
switch. If the power has been
reduced due to module trip alarms, attempt to reset
the associated
PWR MDL
circuit breaker and press
the
MODULE RESET
switch. If fault remains, the
transmitter will resume its alarm condition and
trouble shooting should begin. If the transmitter
returns to full power, the fault has been cleared.
Since the alarm indications are latching, the
ALARM
RESET
will have to be pressed/released.
5.11.1 PA FAIL ALARM: A
PA
(power
amplifier)
FAIL
alarm can occur if the DC input
current to an RF power amplifier falls below a preset
threshold. This may be caused by cabling faults on
the PA input or output or a defective FET. If more
than twelve PA failures exist, the transmitter output
power will be reduced to zero watts. Trouble shoot a
PA fail alarm as follows:
(a) Isolate the RF power module (A thru F)
associated with the
PA FAIL
alarm by opening
the control/monitor panel and noting which RF
power module(s) has active PA alarm lamps
(
Q1 thru Q6 ). If more than twelve PA fail
lamps are on, verify the
COMBINER MATCHING
alarm is also on and the transmitter has been
reduced to zero watts.
NOTE
If a fault condition exists in at least thirteen of the
RF power amplifiers causing an unacceptable match
at the combiner (detected forward power level was
too low for the PA supply voltage level being
applied to the RF power modules), the
COMBINER
MATCHING
alarm lamp will turn on.
(b) If the control/monitor panel's
PA FAIL
lamp is
on or any RF power module PA alarm lamps
(
Q1 thru Q6 ) are on, but no reduction in RF
output power has occurred, the alarm may have
been caused by defective circuitry in the
control/monitor PWB's module PA fail circuitry
or the associated RF power module's power
module interface PWB.
(c) Without removing cables, visually inspect PA
output cable(s) (W1 thru W36) associated with
the suspected PA fail lamp(s) in step (a), noting
W1 thru W6 correspond with PA 1 (
Q1 ) thru 6
( Q6 ) on rf power module A, W7 thru W12 with
PA 1 ( Q1 ) thru 6 ( Q6 ) on RF power module B,
etc. A loose or damaged connection may cause
a PA fail alarm.
When disconnecting cable mating connectors from
J1 thru J6 on the rear of the RF power module to
be removed, ensure the mating connectors at the
combiner end are removed first.
(d) To remove the PA output cable(s), turn off the
RF power module's associated
PWR MDL
circuit
breaker, then disconnect the PA output cable
from the combiner end first. Perform a
continuity check on the cable's center conductor
and shield.
(e) If the PA output cables checked in step (d) are
not defective, the problem may exist within the
associated RF power module,
(f) Trouble shoot the associated RF power module
as described in paragraph 5.7.
5.11.2 MODULE RF DRIVE ALARM: A
MODULE RF DRIVE
alarm can occur if the RF drive
level at the input to an RF power module
(intermediate RF drive) drops to an unacceptable
level. The associated switching power supply will
also be inhibited, and therefore, a
PA VDC FAIL - PWR
SPLY
alarm (
A
thru
F
) will also occur as well as a
reduction in RF output power. If this affects three or
more RF power modules, a
COMBINER MATCHING
alarm should also occur and the transmitter will be
inhibited. Trouble shoot a module RF drive alarm as
follows: