CHPA
S
ERIES
6-6
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6.5 Electrical Preventive Maintenance
Operating voltages and metering accuracy must be verified every six months. If any voltage is
not within the range stated in the maintenance chapter for the assembly, it should be adjusted;
the daily log for the equipment should note the indication before and after adjustment. In
addition, perform the entire initial power-on and checkout as described in Chapter 4, “Initial
Power-on and Checkout.” The assemblies to be checked and adjusted are A1, A2, A5, A7, and
A9. Also test the safety, fault, and alarm circuits. Refer to the appropriate assembly maintenance
section for adjustment. After performance testing (described later in this chapter), it may be
necessary to replace V1 or V2 if the results are not within specification.
6.6 Spare TWT Maintenance and Periodic
Operation of the Amplifier
The following procedure is recommended for conditioning spare TWTs. It is also applicable for
HPAs that are used only occasionally or are turned off for prolonged periods of time (several
weeks or months). The following list presents the conditions for operating the TWT (ranked
from most to least desirable effects on the life of the TWT).
•
Amplifier continuously running in the Beam On state with RF on
•
Beam on, RF off during downtime
•
Beam and heater off during long downtime
•
Heater voltage backed off, beam off during downtime
•
Heater voltage full, beam off during downtime If TWT tubes are stored for extended periods
of time, the TWTs should be operated at least every six months using the following
procedure.
Note: Running the TWT at 0.3 V above the heater voltage on the label can
reduce the TWT life by as much as one half.
Note: If the spare TWT is to be tested, follow the instructions in TWT
Replacement. If the spare TWT is to be tested, follow the instructions in
“TWT Replacement” later in this chapter.
1.
The amplifier should be turned on with no RF drive applied.
2.
Allow the TWT to warm up for at least 5 minutes, but not longer than 15 minutes, before
applying operating voltages.
3.
Enter standard operating mode on the HPA control panel.
4.
Put the amplifier in Transmit.
