Bird Technologies 8578A100GIG - Manual (Page 24)

or moisture, especially to the RF connector. The outside sur-
face of the unit should be wiped free of dust and dirt occa-
sionally. When necessary the inner RF housing and the
outside housing may be cleaned with a mild detergent solu-
tion on a cloth.
Interior
Surfaces
The back and top panel may be removed without difficulty
for cleaning purposes. Give particular attention to the air
intake and exhaust grilles. These grilles must be kept clear
of dust, lint or any matter that may cause restriction of air-
flow. If required, clean the surfaces of the resistors using a
soft, damp cloth. Occasionally check the condition of the RF
coaxial connection. If required, disconnect the unit from the
transmission line and clean the RF connector parts, both
metallic and insulator surfaces. When cleaning these parts
and all other electrical parts, use a dry cleaning solvent that
leaves no residue. Use a cloth to wipe the surfaces.
Enclosure Disassembly
WARNING
Disconnect this unit from RF power sources before any
disassembly for repair or replacements procedures. The
potential for electrical shock exists.
As mentioned previously, the Model 8578A100GIG is field
repairable. To disassemble the enclosure proceed with the
following steps:
1. Remove and retain the 18 Phillips head machine
screws from the back panel.
2. Remove the back panel.
With the RF housing back panel removed, the resistor as-
sembly can be tested and resistors replaced if necessary.
Diagnosing the RF Assembly
The RF section for the Model 8578A100GIG is comprised of
a parallel combination of 9 resistors resulting in a total
nominal resistance of 53.3 ohms. It is normal for the total
resistance to change by a few ohms from measurement to
measurement as this is a characteristic of the type of ce-
ramic resistors used. Wait for the unit to completely cool be-
fore measuring the resistance with a digital multimeter. If
the unit is not adequately cooled, measurement errors can
take place due to the resistors inherent thermocouple char-
acteristic. If there has been a drastic change in the resis-
Bird Model 8578A100GIG Termaline Load Resistor
14