Service Guide N5227-90001 4-11
PNA Series Microwave Network Analyzers Troubleshooting
N5227A Power Up Troubleshooting
If the Fans Are Not Operating
CAUTION The power supply may be in thermal shutdown if the instrument has been operating without
the fans running. Allow the instrument to cool down before troubleshooting.
If all five fans are not operating, suspect a power supply problem or a defective A18 system motherboard.
Refer to “Power Supply Check” on page 4-7 to check the individual supplies. If the supplies are within
specifications, the most probable cause is a defective A18 system motherboard. Refer to “Removing and
Replacing the A18 System Motherboard” on page 7-11.
If only one or two fans are not functioning, and the power supplies are within specifications, suspect the
A18 system motherboard or defective fan(s). Perform the following procedure.
1. Remove the fan bracket, with fans attached, from the analyzer to expose the fan power cable
connections on the A18 system motherboard. Refer to Figure 4-3 for location of these connections. Refer
to “Removing and Replacing the Fans” on page 7-50.
2. Plug in the power cord and measure the fan voltages at all three connectors on the A18 system
motherboard. THIS MUST BE DONE QUICKLY AS THE ANALYZER WILL RAPIDLY OVERHEAT WITHOUT
THE COOLING EFFECT OF THE FANS. DO NOT PLUG IN THE POWER CORD UNTIL READY TO PERFORM
MEASUREMENTS.
Figure 4-3 Fan Power Cable Connections
3. If the correct voltage is present at each connection and the fan connectors are in good mechanical
condition, suspect a defective fan. Refer to “Removing and Replacing the Fans” on page 7-50.
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