AR 10031732, Operating And Service Manual, Page: 37 / 62

Model 4000TP2G4
Rev A 15
operational state of the TWTA, is used as a fault display line until the fault is cleared. Most faults turn HV
off. Faults that do not turn off HV are specified in Table 3-5. When such faults are cleared, the system will
automatically resume the standby state and users may again select the Operate mode.
Some faults (EXTERNAL INHIBIT) will turn off the grid of the tubes to disable RF output while the fault is
being displayed on the screen. HV will remain on during these faults. Once the fault is corrected, the fault will
clear and the system will turn RF back on automatically. This automatic return to operation is provided for
selected faults due to influences external to the TWTA.
Factory Service Screens - A number of screens intended for factory service and calibration are behind
passwords and are not accessible to the user.
System Malfunction Screens - A number of screens are reserved to display error messages. These messages
are not normally seen and indicate a malfunction of the TWTA. System malfunction messages include the
following:
•
Database corrupt
• Communication failure
• Cannot restore
•
CU line voltage too low to operate. System shutdown
In the event that one of these appears, shut off the TWTA and contact an authorized service representative
before proceeding.
CAUTION:
Attempts to operate the TWTA despite control unit problems may result
in loss of the static RAM database and calibration information.