Keysight Technologies N9030B Service Manual page 303

Power Supply/Midplane Troubleshooting
A6 Power Supply Description
Fuse
The A6 Power Supply has no user replaceable fuse. While there is a fuse
internal to the supply this is not meant for field replacement. If the internal fuse
is blown, the power supply has experienced a major failure and should be
replaced.
Standby Supplies
The A6 Power Supply assembly has two standby supplies that should always
be on if the AC input voltage requirements are met. These are the +15VSB and
the +5.1VSB supplies. These supplies are used by the instrument to keep
certain circuits alive even when the power is turned off.
Over Current Protection
The A6 Power Supply assembly has built in over current protection that will
shut down the supply if current draw from the instrument is too great. The
power supply will remain on in over current state for a minimum of 1 second.
The power supply shall turn off no later than 5 seconds after the beginning of
the over current state. The power supply shall remain off until the line voltage
is removed and then reconnected or the front panel power switch is cycled.
Over current shut down does not apply to the standby supplies, the fan
voltage, and the +32VA supply.
Thermal Protection
The A6 Power Supply assembly will protect itself by shutting down if it
overheats. It will also reset itself with no user interaction after the temperature
is reduced by approximately 10 degrees C.
N9030B PXA Signal Analyzer Service Guide 303