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6. With AC power disconnected at its source, retighten the main power line terminal (TB1)
with an insulated screwdriver. The gradual failure of this terminal is indicated by a decrease
of contact pressure caused by thermal expansion and contraction.
7. Check for other defects. These include, but are not limited to, wear, breakage, deterioration,
fungus, excess moisture, and mounting integrity.
6.4.1
Inspecting and Cleaning Air Filters
The air filter at the rear intake of the amplifier should be checked bimonthly and cleaned or
replaced as follows:
1. Inspect the filters for dirt. If necessary, clean with hot water and mild detergent. Dry
thoroughly.
2. Replace the filter.
6.4.2
Checking A3 LEDs and Display
At least once a month, run the CHPA's built-in test to verify proper operation of all indicators.
To run this test, press the Menu key repeatedly until LAMP TEST appears in the display. Press
Enter.
6.4.3
Collector Air System Maintenance
The TWT collector airflow system must be checked to ensure that it is properly transferring the
heat into the airstream and away from the TWT. This means that the measurement of air flow
and temperature and the inspection and elimination of any contaminants restricting the air flow
must be performed periodically. The recommended cycle is three months, but inspection may
be required more often if local air pollution warrants it.
Follow these steps to verify the cooling:
1. Put the CHPA in Standby and allow the TWT to cool before switching off the main circuit
breaker on the HPA front panel. Switch off the main breaker. The control panel display
should be dark.
2. Inspect the exhaust screen and collector radiator for blockage with a flashlight. All collector
radiator fins should be free of material. If not, remove the TWT and the cover on the
collector to blow out the material. Clean the air exhaust screen as required.
3. If the radiator is clean, power up the amplifier.
4. Put the amplifier in Transmit and check the collector air temperature rise by measuring the
intake air temperature and the exhaust air temperature. After 5 minutes of operation, the
exhaust air temperature rise should be no more than 65
and Troubleshooting" chapter of the CHPA Service Manual.
D
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OC
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C. If not, refer to the "Maintenance
o
CHPA SERIES
6-5
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