Service Guide N5242-90001 4-7
PNA Series Microwave Network Analyzers Troubleshooting
N5242A Power Up Troubleshooting
Power Supply Check
NOTE
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 glows yellow. A line switch that
glows yellow indicates that the power supply is providing enough voltage to light the
LED. (However, the voltage may not actually be the correct voltage.)
2. Turn on the instrument power and verify that the line switch glows green. When the
line switch glows green, it is an indication that the power supply has received an “ON”
command and that the power supply can provide enough current to light, at least, this
LED.
3. You can determine which power supplies are functioning by viewing the LED indicators
on the A15 midplane board. Refer to Figure 4-2.
To view the LED indicators, it is necessary to remove the instrument’s outer and inner
covers. Refer to “Removing the Covers” on page 7-6 for removal procedures. To
determine the location of the A15 midplane board, refer to “Top Assemblies, All
Options” on page 6-14.
CAUTION
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 “If Any Supply Voltage Is Missing” on page 4-9 to
determine the cause of the problem.
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 Figure 4-2, the power supply has not suffered a
catastrophic failure. However, the power supply could still be at fault. Continue at
“Measure the Individual Supply Voltages” to verify that the actual supply voltages are
correct.
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 Figure 4-2 for the power supply measurement points on the A15 midplane board.
Refer to Table 4-1 on page 4-9 for the correct voltages.
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