Bird Technologies 8251 Series-Manual - Manual (Page 22)

12
Cleaning
The outside surface of the instrument should be wiped free of dust and dirt when necessary. Excessive dust on the
cooling fins will interfere with heat dissipation. Clean the RF connector, both metallic and insulating surfaces, with a
dry, non-residue forming solvent.
Inspection
Inspect the unit every six months. Check for coolant leakage around the clamping band and the thermoswitch. Also
check for corrosion.
DC Resistance
Measuring the DC resistance between the inner and outer conductors of the RF connector shows changes in the
load over time, a good check of the load resistor’s condition. Under normal operating conditions, the resistor should
provide at least 5,000 hours of operation before requiring any additional service. DC resistance tracking must start
before the load is put into service, and should be measured annually.
Perform the following steps and record the value for future comparison. Make sure that you have an ohmmeter with
an accuracy of ±1% at 50 ohms and that the load temperature is between 20 and 25 °C (68 to 77 °F) before starting.
1. Turn off the RF power and interlock circuitry.
2. Disconnect the RF line.
3. Connect the multimeter test leads to the center and outer conductor of the load
resistor.
4. Compare the measured value with the previous measurement and with the baseline
resistance, measured when the load was put into service.
Note: If the new value differs from either of these by more than 1 ohm this
could indicate a failing resistor.
Figure 7 Measuring Resistance
Coolant
Coolant lifetime will vary greatly depending on operating conditions. For heavy use (full RF power for long times,
high ambient temperature), check the coolant every 500 hours. If the load has only had light duty (fraction of full
power, low ambient temperature), then coolant inspection may only be necessary every 2,000 hours.
Note: Correct any coolant leakage before inspection.
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.