Harris Platinum HT EL 2000HS, Техническое руководство

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Appendix A
RF Amplifier Modules, Platinum Series
A.1
General Information
This procedure is intended to be used as a guide in isolating faults
and troubleshooting Platinum TV RF power amplifiers with
passive bias.
Module faults are most easily verified by swapping the suspected
faulty module with a known working module in another slot. If
the fault follows the module, then the problem is probably
internal to the module. If the fault remains at the same slot after
substituting modules, then the search for the problem should
probably focus on the rest of the transmitter system.
A.1.1
Factory Module Repair
If a failure of a module occurs, the module may be returned to
the factory for repair.
To return a module, contact Harris Repair Department:
By phone: 217-222-8200
By FAX: 217-224-2840
By mail:
Harris Repair Department
P.O. Box 4290
Quincy, Illinois 62305-4290
Include the part number and serial number of the module when
requesting service. Instructions to ship the module will be proc-
essed and communicated to you.
Please provide as detailed information as possible about the
nature of the failure and the operating condition of the module
at the time of failure. This data will help our Repair Department
service your module promptly and efficiently.
If you do not stock a spare module and require another unit for
operation, a spare may be obtained as a loaner unit from the
Harris Repair Department while your unit is shipped to our
factory for repair.
If you are located within the United States, you will be billed for
shipping charges, and if your warranty has expired a nominal fee
will be charged for use of the module.
If you are located outside the United States, the same loaner
service will be offered wherever feasible, but in addition to any
shipping charges you will be responsible for all import duties,
transfer fees or international tariffs.
A.1.2
Local Module Repair
If local repair is necessary, the following troubleshooting guide
and repair procedures are recommended. We strongly recom-
mend reading the appropriate parts of the Theory of Operation,
paragraph A.2 before proceeding.
Optional PA Module Test Fixture (992-8556-002) is needed for
local testing or repair. The fixture will allow testing of a PA or
driver module while using the transmitter as the source of DC
power and RF drive.
A.2
RF Amplifier Modules Theory of
Operation
Three types of RF amplifier modules are used in a Platinum™
Series transmitter:
•
Driver Modules are multiple-stage, high gain RF amplifiers
used primarily to amplify an exciter output and drive sub-
sequent amplifier stages.
•
525 Watt PA Modules are built in driver module configura-
tion. High band modules are biased class A for the two
series configured quarter modules and class AB for the two
parallel output quarter modules.
Low band modules are biased class A for the first quarter module
and class AB for the two parallel output quarter modules.
525 Watt PA modules have a polarizing key on the opposite side
from driver modules. This will prevent interchanging of driver
and 525 Watt PA modules. Due to the differences between 525
Watt PA’s and drivers in bias, gain matching pads and the
adjustment of the protection circuitry they are not interchange-
able without complete testing and readjustment of the protection
circuitry.
•
PA Modules are single-stage, high-power, high-efficiency
amplifiers which use four parallel amplifiers to achieve
output power levels in excess of 1 kW each.
Both drivers and PAs share some common features. Drivers and
PAs both contain smaller amplifier subassemblies called “quarter
modules.”
A multi-pin connector on the rear of each module feeds RF drive,
50 Volts DC, and ENABLE commands to the module, and passes
a fault status signal back to the slave controller. RF output is
passed through a separate coaxial connector. The rear panels of
drivers 525 Watt PAs and 1 kW PAs are keyed differently, so that
lower power units cannot be plugged into PA slots.
The modules are “hot-pluggable,” meaning that they can be
removed or inserted during transmitter operation without turning
the transmitter off. A disable switch is located in the front handle
of each module for this purpose.
The modules protect themselves by automatically disabling
themselves if an improper operating condition is detected. A
protection, control, and monitor (PCM) system monitors the
module’s operating conditions. If all of the conditions are accept-
able, upon an ENABLE signal from the slave controller, the PCM
system will enable the module. If a fault condition arises or the
ENABLE signal is interrupted, the PCM system disables the
module by shutting off the 50 Volts DC.
Descriptions of the various subsystems of Platinum modules are
given below. First, the RF signal paths of the modules are traced;
then, the subsystems are described in more detail.
Refer to the cover sheet of the drawing package for your trans-
mitter to locate the necessary drawing numbers for the modules
and subassemblies.
888-2457-001 A-1
WARNING: Disconnect primary power prior to servcing.