Keysight Technologies N9040B UXA Signal Analyzer Service Guide 229
Power Supply/Midplane Troubleshooting
A6 Power Supply Assembly Troubleshooting
Status Outputs
PWR_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.
PSFAULT_L or PSFAULTn
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
temperature condition. However, there is no way to know at the A6
Power Supply assembly level which one of these conditions may be
the cause of a TTL low level to be on the PSFAULT_L or PSFAULTn
status output.
While any over voltage or over temperature conditions will most
likely be caused by an A6 Power Supply assembly failure, an over
current condition will most likely be caused by another assembly in
the instrument demanding too much current.
If this output is not at a TTL high level the A6 Power Supply assembly
will not turn its non-standby power supplies on, no matter what the
A4 Processor assembly tells it to do.
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