Keysight Technologies Infiniium 90000A Series, Service Manual

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60 90000 A-Series Service Guide
4
Troubleshooting
If any of the fans are turning then they are probably not the cause of your
shutdown problem. (You should still replace any fans that are not turning,
however.)
If this is the case, the next step is to see if the FAN FAIL indicator LED on the upper
right corner of the backplane assembly is lit.
FAN FAIL indicator LED
To check, reset the sensing and shutdown logic by removing the AC power until
the green LED on the motherboard goes out (or just wait 30 seconds). Then
position yourself so you can see the trigger ICs fan on the backplane assembly.
Because this fan is on the bottom of the backplane it is somewhat hidden by the
acquisition assemblies. Look down the backplane board to see it from above.
Trigger ICs fan
Apply AC power and turn the instrument on if it does not start up on its own.
Notice whether the trigger ICs fan is turning. If it is not, replace it and redo this
part of the diagnostic test. If it is turning and the instrument still turns off after 4
seconds or more, then consider these possibilities:
• If any of the case fans were turning and the trigger ICs fan was turning, the
problem is most likely that the rotation sensor on the ICs fan is defective.
Replace the trigger ICs fan and redo this part of the diagnostic test.