Agilent Technologies Infiniium 90000 A, Service Manual

Page: 68 / 148

Chapter 4: Troubleshooting
Over-Voltage Fault
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Over-Voltage Fault
If the oscilloscope turns off without you pressing the front panel power button, the first step is
to unplug the oscilloscope so the +5V standby supply can fully discharge (this takes around 30
seconds). Then plug the oscilloscope back in. Press the front panel power button and count
how many seconds it takes for the oscilloscope to lose power again (once the oscilloscope loses
power, keep it plugged in). If the oscilloscope shuts down almost immediately, it is probably
an over-voltage fault.
Once you have determined that the oscilloscope loses power almost immediately, the next step
is to remove the handle, the outer oscilloscope cover, and the inner top cover. This will expose
the mother board cavity and the top edges of the backplane assembly.
There are three groups of LEDs that indicate over-voltage faults. One group is located near the
center of the top edge of the backplane assembly just above the blue and red SATA cables
(Figure 4-14).
Figure 4-14
If any of these LEDs are on, the backplane assembly must be replaced.
The other two groups of LEDs that indicate over-voltage faults are located along the edges of
the two acquisition assemblies and are visible through the bottom fan opening located on the
left side of the oscilloscope (nearest the rear panel - see Figure 4-15 and Figure 4-16).