Keysight N5264A Service Manual page 45

Troubleshooting
Power Up Troubleshooting
— remove the A17 CPU board
— remove the A16 power supply
— remove the A15 midplane board
— This leaves only the A14 system motherboard installed. If the resistance
measurements are still incorrect, this is the suspected faulty assembly.
If the Fans Are Not Operating
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
page 4-9
specifications, the most probable cause is a defective A14 system
motherboard. Refer to
Motherboard" on page
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
Replacing the Fans" on page
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.
Keysight N5264A Service Guide
to check the individual supplies. If the supplies are within
"Removing and Replacing the A14 System
7-17.
for location of these connections. Refer to
"Power Supply Check" on
7-38.
"Removing and
4-13