Cleaning; Inspecting; Rf Assembly Resistance Test; Dc Resistance Measurement - BIRD Moduload 8640 Series Operation Manual

Cleaning

The outside surface of the unit should be wiped free of dust and dirt when necessary. Clean the RF connector, both
metallic and insulating surfaces, with a dry, non-residue forming solvent.
If dust has collected on the radiator coils, remove the top panel and vacuum the coils. To remove the panel:
1. Remove the screws around the edge of the top panel.
2. Lift the top panel to access the fan power connector then disconnect the fan cable.
3. Remove the top panel.

Inspecting

Routinely check the load's center and outer conductors for visible damage or excessive wear. The coolant level
should be checked once a week, more often if the Moduload is used continuously or under high ambient
temperatures. The coolant level should be above the min. mark on the gauge even when the unit is on. To add
coolant, see
"Changing Coolant" on page 12

RF Assembly Resistance Test

Note: These tests are by no means a necessity to the operation of the load but merely guidelines for
the users information.
Accurate measurement of the DC resistance between the inner and outer conductors 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 resistance over time. Tracking the DC
resistance should start before the unit is first put into service. Perform the following steps and record the value for
future comparison. Resistance measurements should be taken periodically according to use.
Preparation:

Tools: Common hand tools.

Ohmmeter with an accuracy of ± 1% at 50 ohms (or use a resistance bridge).

Use low resistance leads, preferably a short piece of 50 ohm coaxial cable fitted with an appropriate
connector or alligator clips.

Temperature of the load should be stabilized between 20°C to 25°C (68°F to 77°F).

DC Resistance Measurement

Never attempt to connect or disconnect RF equipment from the transmission
Note: It is recommended that this resistance check be performed each time the load is to be used.
1. Turn off RF power and interlock circuitry before making any disconnections.
2. Disconnect the RF coaxial line.
3. Connect the multimeter test leads across the center and outer conductor of the load resistor. See
4. Record the value of the resistance before the load is put into service. Compare subsequent values with the
latest reading. If the values vary more than 2 ohms this could be an indication of a failing resistive element.
.
WARNING
line while RF power is being applied.
Leaking RF energy is a potential health hazard.
Maintenance
.
Figure 6
11