Service Guide N5242-90001 4-11
PNA Series Microwave Network Analyzers Troubleshooting
N5242A 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 three fans are not operating, suspect a power supply problem or a defective
A14 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 A14 system motherboard. Refer to “Removing and Replacing the A14 System
Motherboard” on page 7-16.
If only one or two fans are not functioning, and the power supplies are within
specifications, suspect the A14 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 A14 system motherboard. Refer to Figure 4-3 for location of
these connections. Refer to “Removing and Replacing the Fans” on page 7-60.
2. Plug in the power cord and measure the fan voltages at all three connectors on the A14
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
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