Keysight Technologies X Series Service Manual page 346

Power Supply/Midplane Troubleshooting
A6 Power Supply Description
Control Inputs
There are a number of control inputs for the A6 Power Supply assembly. They
are:
PS_ON
PS_ON is a signal that when pulled low tells the A6 Power Supply assembly to
turn on all of its outputs. This signal comes from the A4 CPU board assembly
and is initiated by pressing the front panel power button.
DITHER
DITHER is an AC coupled analog signal going to the supply that is used to
frequency modulate the power supply switching frequency for the purpose of
lowering any power supply related interference.
OFFn
OFFn is an input that is to be used only as a "Panic Stop". This signal can be
used for such functions as an emergency over temperature shut down. This
type of shut down is a last resort and does not perform the recommended
operating system shut down of the instrument.
TEMP_SEN
TEMP_SEN is an analog input to the fan speed control circuit. The fan runs at a
slow speed at room temperature to reduce noise and then will ramp up to full
speed as the temperature increases.
Control/Status Outputs
There are a number of control and status outputs for the A6 Power Supply
assembly. They are:
PWROK_H
PWROK_H is used to verify that the +12V D, +5.1V D, and +3.35V D are all on
and within specification. A TTL high level on this output brings the CPU out of
reset and initiates the instrument boot up process.
LINE_TRIG
LINE_TRIG is a TTL level signal that is synchronous to the AC line input. This
signal is typically used in signal analyzers to trigger an instrument sweep
synchronous to the AC power line.
PS_TEMP
PS_TEMP is a read out of the internal temperature of the power supply.
PS_FAULT
PS_FAULT will be a TTL low level signal to indicate that the supply is
experiencing an over voltage, over current, or over temperature condition.
346 Keysight N9010A EXA Service Guide