10 000 WATT FM BROADCAST TRANSMITTER
FM10
Page 5-6
01 October 2002
(d) Disconnect suspect PA's PA output cable (W1
thru W36) from the combiner end (see table 9-
7) and connect it through an in-line power
meter to a 50 ohm, 500W load.
(e) Set the associated RF power module's PWR
MDL
circuit breaker to ON
.
(f) Monitor the power meter reading at the 50 ohm,
500 watt load. If the power meter reading is
less than 50 watts, then the suspect PA is not
functioning properly. If the power meter
reading is normal, the problem may exist with
the power module interface PWB's associated
PA failure detection circuitry.
(g) Set the associated RF power module's PWR
MDL
circuit breaker to OFF
and reconnect the
PA's output cable to its combiner input.
(h) Repeat steps (c) thru (g) for other suspect PAs.
(i) Remove the RF power module(s) containing
non-functional PAs as detailed in paragraph
5.7.
REPLACEMENT OF AN RF POWER MODULE
5.7
Replace an RF power module as follows:
RF power modules contain solid state devices that
may be damaged if they are subjected to excessive
heat or high voltage transients. Every effort must
be taken to ensure circuits are not overdriven and
they are not disconnected from their loads while
turned on.
(a) The RF power modules are referred to as 'A'
thru 'E' in the following procedures. Refer to
figures MD-1 and MD-2 as an aid to
identifying a specific module.
(a) The PWR MDL circuit breakers, which control
the application of PA volts to the RF power
modules, are located on the circuit breaker
panel which is located at the front, lower
portion of the transmitter. Refer to figure MD-
1 to locate the circuit breaker panel and then to
figure MD-5 to locate a specific PWR MDL
circuit breaker.
5.7.1 RF POWER MODULE REMOVAL:
Remove a defective RF power module as follows:
NOTE
PWR MDL circuit breakers labelled A thru F and IPA
are associated with RF power modules identified as
A thru F and the IPA module.
(a) Set the PWR MDL circuit breaker that applies
PA volts to the RF power module to be
removed to OFF (toggle down).
(d) Gain access to the rear of the RF power
modules by removing the upper panel from the
rear of the transmitter (refer to figure MD-2).
Retain all attaching hardware.
The RF coaxial cables interconnecting the RF
power module's RF outputs and the RF combiner's
inputs must be disconnected from the RF combiner
end before they are disconnected from the RF
power module. Failure to observe this
disconnection sequence will cause an impedance
mismatch to be reflected back to the RF combiner
and may cause irreversible damage to the
operational RF power modules.
(e) Identify and record the 'W#' of the coaxial
cables connected to J1 thru J6 of the RF power
module to be removed, noting they should be
the same as the cables identified in table 5-3.
Do not remove any coaxial cables from the RF
power module at this time.
(f) At the RF combiner, locate the coaxial
connector terminating each of the six coaxial
cables identified in step (e) and disconnect them
from the RF combiner.
(g) Disconnect the RF output coaxial cables
identified in step (e) from J1 thru J6 of the RF
power module to be removed.
(h) Identify and record the 'W#' of the RF drive
coaxial cable connected to J9 of the RF power
module to be removed, noting it should be the
same as the cable identified in table 5-3. Do
not disconnect this coaxial cable from the RF
power module at this time.
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