Keysight N5227A Service Manual page 81

PNA Series Microwave Network Analyzers
N5227A
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
specifications, the most probable cause is a defective A18 system motherboard. Refer to
Replacing the A18 System Motherboard" on page
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
to "Removing and Replacing the Fans" on page
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
Service Guide N5227-90001
to check the individual supplies. If the supplies are within
7-11.
Figure 4-3 for location of these connections. Refer
7-50.
"Removing and Replacing the Fans" on page
Troubleshooting
Power Up Troubleshooting
"Removing and
7-50.
4-11