Specifications

on those Drivers. Refer to the Troubleshooting section of
the RF Amplifier.
6.4.5.2 Fault Sensing
a. If the above checks do not reveal the source of the prob-
lem, it is possible that the RF drive level sensing circuit
has failed. Refer to the Troubleshooting section of the
Driver Encoder, to determine the fault.
6.4.6
RF Amp Temp
If the transmitter is operating at reduced power or has shut itself
off, and the RF AMP TEMP/ANALOG INPUT POWER
FOLDBACK Control front panel LEDs are illuminated RED,
then the temperature of RF1 or the ambient air has exceeded 70
degrees C. The amount of power reduction depends upon how
long the transmitter has been operating in the overtemperature
condition. A prolonged over-temperature condition will eventu-
ally turn the transmitter off.
a. Measurethe intake air for the left PAcabinet, if it is greater
than 50 degrees C then additional cooling will be required
for the transmitter facility.
b. Check the intake air filters of the transmitter. A plugged
or dirty filter can cause a lack of proper airflow and
excessive heat in the PA compartments. Replace as
needed.
c. Verify that the exhaust is not restricted. Correct as needed.
d. Check the tuning of the transmitter. Mistuning of the
transmitter can cause the RF Amplifiers to run less effi-
ciently therefore generating more heat.
e. If the intake air temperature is less than 50 degrees C, the
filters are clean and the exhaust is unrestricted, it is
possible that RF1 is defective.
WARNING
ENSURE THAT THE TRANSMITTER IS TURNED OFF AND ALL
PRIMARY POWER IS TURNED OFF AT THE WALL DISCONNECT
SWITCH BEFORE OPENING ANY DOOR OR PANEL. BEFORE
REMOVING PANELS OR OPENING DOORS, VERIFY THAT THE
RF AMP POWER SUPPLY IS DISCHARGED BY CHECKING
“PA+VDC” ON THE FRONT PANEL MULTIMETER. USE A VOLT-
METER TO VERIFY THE POWER SUPPLIES HAVE BEEN DIS-
CHARGED PRIOR TO TOUCHING ANY COMPONENTS.
1. Turn off the transmitter and open the left cabinet inner
front door.
2. Remove RF1 and feel the heatsink. If it is extremely
hot compared to the other RF Amplifier heatsinks,
troubleshoot the amplifier using the Troubleshooting
portion of Section G, RF Amplifier.
f. If the amplifieris not hot, it ispossible that thetemperature
detector circuit, or the temperature sensor and cable as-
sembly is defective.
1. Turn on the transmitter, and monitor TP3 on the Modu-
lation Encoder A29 with a voltmeter.
2. If voltage at TP33 is less than the voltage at U37-8 or
U37-6, refer to the Troubleshooting portion of Section
L, Modulation Encoder to determine the cause.
6.4.7
RF Amp Fuse
If the transmitter is operating at reduced power and/or the RF
AMP FUSE Control front panel LED is illuminated RED, then:
a. One or more fuses (230VDC or RF Drive) on one or more
RF Amplifiers is open.
b. RF drive on one or more RF Amplifiers is low, or
c. One or more 230VDC fuses on a Fuse Board is open or
any combination of the above.
Note
The fuse detector circuit has no function other than to illuminate
the LED.
To determine which RF Amplifier(s) has an open fuse(s):
a. Open the left, center, and right front doors and observe
each of the five Modulation Encoders.
b. If any of these Modulation Encoders has DS6 illuminated
RED, then an RF Amplifier(s) connected to that Modula-
tion Encoder has an open fuse(s).
For example:
Suppose that DS6 is illuminated RED on Modulation En-
coder A29, then any RF Amplifier, RF1 through RF31 and
RF152, could have an open fuse(s). We will be using this
examplefor the rest of the discussion, it applies to all other
Modulation Encoders. Which type fuse(s) is open depends
upon the symptoms or other indicators.
c. Turn on the transmitter and observe DS1 and DS2 on RF
Amplifiers RF1 through RF31 and RF152, if any of these
indicators is illuminated RED, then the +230VDC fuse
associated with that RF Amplifier is open. To repair the
module refer to the Troubleshooting portion of Section G,
RF Amplifiers.
d. If DS1 and DS2 are not illuminated RED on RF Amplifi-
ers RF1 through RF31 and RF152, then use the Control
Multimeter Probe on the PROBE +VDC (0-30) scale and
measure the voltages on TP2, TP16, TP17, and TP18 on
the A29 Modulation Encoder. Normally these test points
should measure 12.5VDC. If one measures 7.5VDC or
less then check all of the fuses for that group of eight RF
Amplifiers.
For example:
If TP2 measures 7.5VDC, then ohmmeter check all of the
fuses(+230VDC andRF) on RF AmplifiersRF24 through
RF31. If an open fuse(s) is found troubleshoot the mod-
ule(s) referring to the Troubleshooting portion of Section
G, RF Amplifier. If needed refer to the overall wiring dia-
gram and the Modulation Encoder section to determine
which groups of eight RF Amplifiers are connected to
each fuse detector.
888-2339-002 6-5
WARNING: Disconnect primary power prior to servicing.