Manual

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