AR 10027190, Operating And Service Manual

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Models 200T18G26z5A/200T26z5G40A
Rev – 10
CAUTION:
Never operate the TWTA without a matched output load rated for at
least 300 watts, continuous. Full reflected power may irreparably
damage the TWT. Even with no drive, “looping” oscillation can result in
RF output high enough to damage the tube if it is operated without a
load. The VSWR detection, isolator and foldback circuit is provided to
protect the tube from progressive failure or mismatch of the output load;
it should not be relied on for protection from the absence of a load.
If an external isolator is installed at the output of the TWTA, either the isolator should have a load capable of
dissipating the full output of the TWTA or the isolator load should be provided with a temperature sensing
switch. The temperature switch should be normally closed, self-resetting, and with a temperature rating such
that there is no possibility of damaging the load by overheating before the switch opens. The TWTA may be
interlocked with the switch by connecting it between pins 3 and 4 of the external interlock connector (J2). If
no external isolator is used, install a jumper between pins 3 and 4. See section 3.2.6, External Interlock
Connector, below.
3.2.6 External Interlock Connector
The TWTA is provided with an external interlock capability via a 15-pin female D-sub connector, J2. To
enable the high voltage power supply, it is necessary to provide continuity between J2 pins 3 and 4. If the
amplifier shuts down because the interlock was opened, it will be necessary to reset the system to return to
standby (see
System shutdown screen in Section 3.4). There is an internal jumper between J2 pins 1 and 2; a
continuity check through these pins can be used to verify the presence of the amplifier in the instrumentation
system. Users may adopt this interlock feature to disable the RF output for either equipment protection or as
a backup for personnel protection.
Pin Title Function
1 INTERNAL JUMPER Internal jumper from pin 1 to pin 2
2. INTERNAL JUMPER Internal jumper from pin 1 to pin 2
3.
EXTERNAL INTERLOCK
SUPPLY
Disables High Voltage power supply in continuity is opened from pin 3 to pin 4.
4.
EXTERNAL INTERLOCK
RETURN
Disables High Voltage power supply in continuity is opened from pin 3 to pin 4.
5-9. NOT USED
10. INHIBIT SUPPLY Disables RF power output if continuity is opened from pin 10 to pin 15.
11-14 NOT USD
15 INHINIT RETURN Disables RF power output if continuity is opened from pin 10 to pin 15.
CAUTION:
Do not rely on the external interlock for personnel protection. The intent
of the external interlock feature is to disable the RF output for equipment
protection. Use proper operating and safety procedures to insure that
power is removed for personnel safety.
3.2.7 External IEEE-488 Connector
The TWTA is provided with a standard IEEE-488 connector on the rear panel. If the TWTA is mounted in a
bench-top cabinet, the mating connector should be a straight-entry cable type, not a side-entry type.