Maintenance
10
Preventative Maintenance
Due to the basic simplicity of construction, the major requirement for preven-
tive maintenance is to keep the equipment clean.
RF Load Resistor
Preparation:
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Tools: Common hand tools
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Ohmmeter with an accuracy of ± 1% at 50 ohms.
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Use low resistance leads, preferably a short piece of 50 ohm coaxial
cable fitted with alligator clips.
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Temperature of the load between 20°C to 25°C (68°F to 77°F)
Accurate measurement of the DC resistance between the inner and outer con-
ductors of the RF input connector will provide a good check of the condition of
the load resistor. Checking the DC resistance is simply used to measure a
change in the condition of the resistor over time. The tracking of the DC resis-
tance must start
before
the resistor is first put into service. Perform the follow-
ing steps and record the value for future comparison. Check and record the
resistance of the load periodically according to use.
Measuring the DC Resistance
1. Turn off RF power and interlock circuitry before any electrical disconnec-
tions are made.
2. Disconnect the RF coaxial line.
3. Connect the multimeter test leads across the center and outer conductor of
the load resistor. Refer to figure 2 for placement of the leads.
4. Record the value of the resistance
before
the load is put into service. Com-
pare subsequent values with the latest reading. If the values vary more
than 2 ohms this could be an indication of a failing resistive element.
Note:
These tests are by no means a necessity to the operation of
the load but merely guidelines for the users information.
Note:
It is recommended that this resistance check be performed
each time the load is to be used.
Figure 1 Measuring DC Resistance
WARNING
Never attempt to connect or disconnect RF equipment from the transmission
line while RF power is being applied. Leaking RF energy is a potential
health hazard.
Summary of Contents for TERMALINE 8745 Series
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