Keysight Technologies Infiniium MSOV 084A, Service Manual

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70 Infiniium V-Series Oscilloscopes Service Guide
4
Troubleshooting
Follow these steps to diagnose a main fan failure:
1
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).
2
Move to the left side of the oscilloscope so you can see the case fans.
3
Apply AC power to the oscilloscope and turn it on if it does not start up
automatically. Visually check to see if any of the fans are not turning. If none of
the fans are turning, it is likely a problem with the high side drive circuitry for
the case fans. In that case, you would replace the backplane assembly.
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 the oscilloscope still shuts down, follow these steps:
1
Replace all the case fans.
2
Reset the logic by removing AC power for 30 seconds and make all of the case
fans so they cannot rotate. For example, have two people hold the four fan hubs
or insert an object between the blades of each of the fans.
3
Power the oscilloscope back on. If it shuts down again, the fan sensing and
shutdown function is operating properly. Replace the backplane.
If the PRED FAN FAIL LED is lit
In addition to three case fans, there is also a single fan attached to the backplane
assembly that cools the trigger ICs. It is possible that this fan failed, or that the
rotation sensor for the fan failed. This sensor lets the oscilloscope know that the
fan is turning. If the sensor is faulty, the oscilloscope may think the fan is not
working when it actually is.
If the PRED FAN FAIL indicator LED on the backplane assembly is lit, the system
thinks there is a trigger ICs fan failure. 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 assembly. Look down the backplane board
to see it from above. (See the following figure.)
WARNING
INJURY CAN RESULT! The following procedure requires you to touch fan hubs with
objects or to use objects to stop the fan blades from moving. Use caution when
working near the fan blades with the cover removed from the oscilloscope. The
cooling fan blades are exposed on one side and can be hazardous. Be careful not to
let the moving fan blades come in contact with any part of your body.