XT-50, XT-80, and XT-100 Amplifiers Installation 2-11
•• High Voltage Fault (Pin R). (Active = low) When active indicates
there is a high voltage fault within the amplifier when Pin R (+) is
connected by open collector to ground
(Pin W). Maximum open voltage is 20 volts and maximum
switched current is 3 mA. The switch is an isolated photo-coupler.
A high voltage fault is typically an indication of a serious power
supply failure.
•• Fan ON High (Pin S). (Active = low) When active, indicates that
the TWT has heated up to the point that the fan must run at its
manufacturer's rated voltage when Pin S (+) is connected by open
collector to ground (Pin W). Maximum open voltage is 20 volts and
maximum switched current is 3 mA. The switch is an isolated
photo-coupler.
•• Summary Fault (Pin T). (Active = low) When active, indicates
there is a fault within the amplifier when Pin T (+) is connected by
open collector to ground (Pin W). Maximum open voltage is 20
volts and maximum switched current is 3 mA. The switch is an
isolated photo-coupler.
•• Fan Lock (Pin U). (Active = low) When active indicates that the
fan is locked when Pin U (+) is connected by open collector to
ground (Pin W). Maximum open voltage is 20 volts and maximum
switched current is 3 mA. The switch is an isolated photo-coupler.
A Fan Lock signal is caused by either a fan failure or some object is
interfering with the rotation of the fan.
•• Control/Status Return (Pin W). Common return.
Analog Status Circuits
•• RF Output Power (Pin b). This pin is not active on the
Multi-Band TWTA.
•• Helix Current (Pin D). The TWT's helix current may be determined
by monitoring the voltage in Pin D. There is 2 mA of current for
each volt measured.
•• High Voltage Monitor (Pin L). The high voltage level may be
determined by monitoring the voltage in Pin L. This output is
proportional to the high voltage (1V/1000 VDC).
•• Analog Signal Return (Pin N). Common return.
•• TWT Temperature (Pin P). The TWT's collector temperature may
be determined by monitoring the voltage on Pin P and referring to
Figure 2-12.
• Reflected Power (Pin c). The detector output is nominally 2VDC
for a VSWR of 2.5:1.
Output Voltage Circuits
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