Specifications
6.4.4.1 Loss of Driver Amplifiers
a. Turn the transmitter on, and observe DS1 and DS2 on all
Driver Amplifiers.
1. If any of theseindicators turn RED during the step-start
sequence the Driver Amplifier side associated with the
indicator will need to be repaired. Refer to the Trou-
bleshooting section for the RF Amplifier.
Note
If Driver amplifiers have failed, it may be possible to return to
normal operation without repairing the RF Amplifiers immedi-
ately. Refer to Section 6A, Emergency Operating Procedures,
Paragraph Title: Driver Amplifier Failure.
6.4.4.2
Loss of 115VDC Supply.
a. Separately select LEFT and RIGHT DRIVER +VDC
positions on the Driver Multimeter and turn on the trans-
mitter.
1. If the meter does not deflect upscale, troubleshoot the
+115VDC power supply.
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.
b. If the supply is ok, check fuses F1 and F2 in the rear of
the Driver Compartment.
c. If the fuse(s) check ok, test for continuity from the F1 and
F2 clips to the respective fuse clips on the Driver Ampli-
fiers.
d. If either fuse is open, measure the resistance from the fuse
clip to ground.
e. If a short is found, pull all of the Driver Amplifiers and
recheck.
f. If still shorted, suspect a filter capacitor.
6.4.4.3 Observe DS3 on All Driver Amplifiers
a. If DS3 on the Driver Amplifier(s) is not illuminated
GREEN during the step-start sequence:
6.4.4.4 No Driver Amplifier(s) RF Input
NOTE
Refer to “Measuring RF Drive” at the end of this section for the
following discussion.
a. With an oscilloscope, determine that the RF drive wave-
form on all Driver Amplifiers is present and at the correct
frequency.
1. If there is little or no RF drive, refer to the overall
diagram to troubleshoot the circuit back to the Pre-
driver Tuning circuits.
6.4.4.5 Loss of Turn-On Command
a. Check the Driver Amplifier turn-on signals on the Driver
Encoder board at J1-1, 3, 11, 13, 15, and J2-1. Each point
should be approximately -2VDC.
b. Check the Driver Amplifier turn-on signals on the Driver
Encoder board at J2-11, 13, and 15.
NOTE
Driver Amplifiers D8 through D10 are frequency determined.
Refer to the Detailed Circuit Description in the Driver Encoder
section to determine if these Driver Amplifiers should be turned
on.
c. Check the Driver Amplifier turn-on signals on the Driver
EncoderboardatJ2-1,3,5,and7.
1. Only D11 and D12 should be turned on during the
step-start sequence.
d. If these outputs are not correct, refer to the Troubleshoot-
ing section for the Driver Encoder.
e. If the voltage is correct, use the overall wiring diagram
and the Driver Combiner schematic to check continuity
up to the Driver Amplifier inputs.
Note
If Driver Encoder outputs are not correct, it may be possible to
return to normal operation. Refer to Section 6A, Emergency Op-
erating Procedures, Paragraph Title: Driver Encoder Bypass-
ing.
6.4.4.6 Failed Driver Tuning Components
It is possible for one of the components in the Driver Tuning
board to have failed and therefore de-tune the output. Failed
components like capacitors and inductors can sometimes be
identified by checking for abnormal heating after operating for
a short time. Test the relay switching circuits and refer to the
Frequency Control Interface board to determine if the correct
bandswitched outputs exist.
6.4.4.7 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.
6.4.5
High Drive
If the transmitter has turned itself off, and the HIGH DRIVE
Control panel LED is illuminated RED, the RF drive level to the
RF Amplifiers is over the upper limit. If there is too much drive:
6.4.5.1 Too Many Drivers Turned On
a. Turn on the transmitter and observe DS3 on each Driver
that is not normally operational at the current frequency.
b. If DS3 turns GREEN during the step-start sequence,
monitor the turn-on lines at J2 on the Driver Encoder for
the Drivers that are turned on but should not be in service.
c. If during the step-start sequence, any of these lines go to
-2VDC refer to the Troubleshooting section of the Driver
Encoder.
d. If the turn-on signals for these Drivers does not go to
-2VDC, but DS3 is illuminated GREEN during the step-
start sequence, troubleshoot the turn-on/turn-off circuits
6-4 888-2339-002
WARNING: Disconnect primary power prior to servicing.