Keysight NFA Series Noise Figure Analyzers Service Guide 53
Boot Up and Initialization Troubleshooting
Potential Problems During Boot Process
Figure 2-3 A7 Midplane Board +5.1V LED
Is the +5.1SB LED on the A7 Midplane board on?
If yes:
After verifying that the connections from the front panel Standby LED back
to the A4 CPU board are not at fault, replace the A4 CPU board.
If no:
Replace the A6 Power Supply assembly.
All DC power supplies come from the A6 Power Supply assembly.
However, the most convenient measurement location for all the DC
supplies is the A7 Midplane. All power supply LED's are accessible once
the instrument cover has been removed.
Before replacing the power supply, verify the midplane and motherboard
interconnects are mechanically secure.