1 kW Termaline Coaxial Load Resistor Series 8251
9
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
5
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.
1.
Remove the load resistor (Refer to “Load Resistor” on page 18).
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.
WARNING
Disconnect the unit from all power sources before servicing. The unit may be energized
from multiple sources. The potential for electric shock exists.
CAUTION
Use only Bird coolant, P/N 5-1070, to prevent damage to the load.
