Keysight Technologies Infiniium 90000A Series, Service Manual

Page: 69 / 136

Troubleshooting
4
90000 A-Series Service Guide 69
Motherboard Verification
If you have been through the Power Supply Troubleshooting section of this chapter
and the oscilloscope still does not stay powered up, the problem may be with the
motherboard. To diagnose this problem, follow these steps.
1
Remove the handle, outer case, and top shield.
2
Turn the oscilloscope on.
If the unit beeps once after about 5 to 10 seconds but fails to boot up, the
motherboard is defective and needs to be replaced.
If the unit fails to beep after it is powered on, then measure the potential
relative to the chassis at pin 9 of J1201 (see following figure). You should
measure about 3.3 V. If the potential you measure is correct, but the unit still
has not beeped and started up, the motherboard is defective and needs to be
replaced.
3
If the potential you measure is not correct, shut the oscilloscope down and
unplug the AC cord from the rear of the instrument.
4
Unplug the front panel power cable, the two large power cables that go to the
motherboard (J1201 and J1202), and the red and blue SATA cables (J900 and
J901) from the backplane assembly. Do not allow the two SATA cables to touch
the backplane assembly and cause a short circuit.
5
Plug the AC power back into the oscilloscope and turn the unit on if it does not
come on automatically.
6
Measure the potential relative to the chassis at pin 9 of J1201 again.
If you measure the required 3.3 V, the motherboard is defective and needs to be
replaced.
If you did not measure the correct voltage, the backplane assembly is defective
and must be replaced.