N9030B PXA Signal Analyzer Service Guide 305
Power Supply/Midplane Troubleshooting
A6 Power Supply Assembly Troubleshooting
Control Inputs
POWER_ON
POWER_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 Processor board assembly and is initiated by pressing the front
panel power button.
If the instrument will not turn on be sure that this line is being pulled
low by either measuring the voltage level at Test Point 518 on the A7
Midplane board assembly or by viewing the status of the
POWER_ON_L LED. See the "A7 Midplane Board Assembly
Troubleshooting" on page 310 for detailed information on the
location of this test point and LED as well as the expected status for
both when the instrument is operating properly.
Status Outputs
POWER_OK
The POWER_OK status output is an indication of whether or not all of
the digital power supply voltages are up to their specified voltage
levels or not. If all of these supplies are working properly this output
line will be at a TTL high level. If this output is not at a TTL High level
the instrument CPU will not come out of its reset state and will not
boot-up. Once this output goes to a TTL high level the instrument
CPU will start its boot-up process and the POWER_ON_L line coming
from the A4 Processor assembly will go to a TTL low level which will
tell the A6 Power Supply assembly to turn on the rest of it output
voltages.
If the A6 Power Supply assembly is suspected of causing the
instrument to not power on properly the status of this output can be
verified by either measuring the voltage level at Test Point 506 on the
A7 Midplane board assembly or by viewing the status of the
POWER_OK LED. See the A7 Midplane Board Assembly
Troubleshooting section in this chapter for detailed information on
the location of this test point and LED as well as the expected status
for both when the instrument is operating properly.
FAULT_L
The FAULT_L status output is an indication of whether or not there is
a fault detected by the A6 Power Supply that is keeping it from
powering on properly. If all of the required conditions to turn the A6
Power Supply assembly on properly are being met this status output
line will be at a TTL high level. The conditions that could cause this
status output line to be at a TTL low level include that of an over
current condition, an over voltage condition, and an over
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