Power Supply Check - Keysight Technologies N5221A Service Manual

Troubleshooting
Power Up Troubleshooting

Power Supply Check

There are no fuses to replace within the power supply. If you determine
that the power supply is the failed assembly, replace the power supply.
A catastrophic failure in the power supply can be determined by observing the
line switch and the power supply LED indicators:
1. Ensure that the instrument is plugged in with the power switch in the
standby position (power not switched on). Verify that the line switch
displays a yellow light. A line switch that displays a yellow light indicates
that the power supply standby line is active and functional)
2. Turn on the instrument power and verify that the line switch now displays
a green light. When the line switch displays a green light, it is an
indication that the power supply is active and does not sense an
over-current condition.
3. You can determine which power supplies are functioning by viewing the
LED indicators on the A15 midplane board. Refer to
To view the LED indicators, it is necessary to remove the instrument's
outer and inner covers. Refer to
removal procedures. To determine the location of the A15 midplane board,
refer to
Do not operate the analyzer with the outer cover removed for more than
30 minutes, as this could cause the analyzer to overheat which could
result in costly damage.
4. If any power supply voltage is missing, it is likely that the problem is a
defective A16 power supply, the A15 midplane board, or another assembly
that is loading down the A16 power supply. Continue with
Voltage Is Missing" on page 4-11
5. If the line switch is lit correctly, and all the power supply voltages appear
to be present, as indicated by the LEDs as shown in
supply has not suffered a catastrophic failure. However, the power supply
could still be at fault. Continue at
Voltages"
Measure the Individual Supply Voltages
Measure the power supply voltages using a digital multi-meter. Use the point
labeled ACOM as ground reference for analog supplies and the point marked
DCOM as ground reference for digital supplies.
Refer to
midplane board. Refer to
Keysight N5221A/22A Service Guide
"Top Assemblies and Cables, All Options" on page
to verify that the actual supply voltages are correct.
Figure 4-2 for the power supply measurement points on the A15
Table 4-2 on page 4-11
Figure
"Removing the Covers" on page 7-6
to determine the cause of the problem.
Figure
"Measure the Individual Supply
for the correct voltages.
4-2.
for
6-16.
"If Any Supply
4-2, the power
4-9