Harris Gates One 994 9202 002, Technical Manual

Page: 35 / 110

SECTION IV
TROUBLESHOOTING
4.1.
Introduction
This section of the technical manual con-
tains overall troubleshooting procedures for
the GATES Series™ AM Transmitter. As
needed, references are made to the individu-
alized sections of the manual.
4.2.
Definition of
Front Panel Indicators
UNDERDRIVE LED When lit is an in-
dication of low or no RF drive to the PA
module(s).
VSWR LED Indicates a mismatch at the
transmitter output or the TEE section of the
Output Network.
SUPPLY VOLTAGE LED The DC out-
put of the high voltage supply has exceeded
the maximum threshold of 290 volts.
SUPPLY CURRENT LED The current
draw from the high voltage supply exceeded
normal values.
AUTOMATIC CUTBACK LED Indi-
cates the transmitter has reduced to a lower
power level on its own because of a persist-
ing overload condition.
PDM KILL LED Indicates that the
transmitter is being muted by either an ex-
ternal command, or by the transmitter’s step
start circuitry failing to complete its con-
nections.
PLUS and MINUS 12 VOLTS When lit,
indicates presence of Controller supply
voltage.
REMOTE LED Indicates that the re-
mote inputs are enabled. This does not in-
hibit any local control functions.
LOCAL LED Lights when the transmit-
ter can only be controlled locally.
PDM FAULT SENSING The PDM fault
sensing LED’s indicate a significant imbal-
ance in the PDM operation, resulting in a
PDM Amplifier doing more or less than its
share of work.
PA FUSE INDICATORS When lit indi-
cate one or more fuses are blown in the
corresponding PA module.
AIRFLOW SENSOR In addition, trans-
mitters manufactured in December 1995
and later are equipped with an Airflow Sen-
sor which shuts the transmitter down, and
produces an audible alarm in the event a fan
failure is detected. This audible alarm is a
continuous 2.8 Khz tone, plus a visual indi-
cator provided on one of the Airflow Sensor
boards. If the transmitter shuts down due to
a fan failure, the transmitter can be turned
back on. However, it will shut down in 1 to
2 minutes when the fan failure is again
detected.
4.3.
Symptom: Transmitter Will
Not Turn On - None of the
Green LED’s on the Power
Level Switches are Illuminated
4.3.1.
Possible Causes
4.3.1.1.
Loss of AC Power
Look at the +/-12V LED’s on the Control-
ler panel. If these are not illuminated, look
at the amber indicators down by the Low
Voltage circuit breaker at the bottom of the
cabinet. If the circuit breaker is up and both
indicators are illuminated, the AC power is
getting to the transmitter.
4.3.1.2.
Control Supply Failure
Loss of the +/-12V supplies, as indicated
by the +/-12V LED’s being extinguished,
points to a failure of one of the regulators
(U32 or U33) on the Controller board, or a
short circuit on the Controller.
Check fuses F2 and F3 on the Interface
board. These are in line with the +/-20 volts
to the Controller. A blown fuse most likely
indicates excessive current draw by the
Controller.
4.4.
Symptom: Green Power Level
Status LED’s Illuminate, but
the Primary Contactors Do
Not Energize and No Overload
LED’s Illuminate
The contactors normally produce an audi-
ble clunk as they close, and result in Supply
Voltage registering on the Multimeter.
4.4.1.
Possible Causes
4.4.1.1.
Phase Monitor (3
∅
FIVE only)
Check to see if the LED on the Phase
Monitor relay in the contactor drawer is
illuminated. If it is not, there may be a loss
of phase, low line voltage, or improper ad-
justment of the Phase Monitor relay. Al-
though less common, there may also have
been a phase reversal by the power com-
pany.
4.4.1.2.
Blown fuse
Check fuse F1 on the Interface board. Also
make sure 24 VAC is present at F1 anytime
AC power is applied to the transmitter.
4.4.1.3.
Open Interlock
Make sure the rear panel is in position and
fastened. Make sure the panel closure actu-
ally closes the interlock switch. A “click”
should be audible as the panel is pushed
shut.
WARNING
BEFORE PERFORMING THE FOLLOW-
ING STEP, DISCONNECT ALL POWER
FROM THE TRANSMITTER AND USE
GROUNDING STICK TO DISCHARGE ALL
POINTS BEFORE TOUCHING THEM.
4.4.1.4.
Failsafe Interlock Open
A closure should be provided between
TB1-1 and TB1-2 of the Interface Board for
normal operation. If a remote control sys-
tem or other equipment is connected to
these terminals, check for the closure at the
Failsafe terminals. Turn the low voltage
OFF and ground the terminals with a
grounding stick before using an ohmmeter
to check for a closure at TB1-1 and TB1-2.
4.4.1.5.
Interface board Output
With AC power applied and any of the ON
pushbuttons depressed, 24 VAC should ap-
pear at TB1-2 on the Interface board. It will
not be necessary to install the rear panel for
this test.
4.4.1.6.
Open Contactor Circuit
If the voltage checks okay at TB1-2 in the
preceding step, then it is apparent that the
K1 coil circuit is open. This would include
the back panel interlock, Failsafe, the coil
of K1, the Airflow Sensor, and the Phase
Monitor relay (3
∅
FIVE only).
4.4.1.7.
Contactor Control Signal
If 24 VAC does not appear at TB1-1 and
TB1-2 when any of the ON pushbuttons are
depressed, check for the presence of a con-
trol signal at R18 on the Interface board.
About 5 volts DC should appear on the input
side of R18 in an ON condition. If not there,
trace its origin at the Controller.
4.5.
Symptom: One or Both Pri-
mary Contactors Energize, But
There Is No Power Output
4.5.1.
High Voltage Supply Failure
Check the Supply Voltage on the Multime-
ter. This should be 250-265 volts with the
transmitter in any of the ON modes. If the
supply voltage is zero, a High Voltage Sup-
ply problem is indicated. Check the step
start resistors in the contactor drawer. An
open step start resistor would indicate a
failure in the high voltage supply, most
likely a shorted rectifier.
Also check the condition of the MOV
devices on TB2 in the contactor drawer. A
blown MOV would be an indication of a
significant power line surge or transient.
Rev. T: Jan. 1996 888-2314-001 4-1
WARNING: Disconnect primary power prior to servicing.