Keysight Technologies Infiniium 90000A Series, Service Manual

Page: 53 / 136

Troubleshooting
4
90000 A-Series Service Guide 53
Power Supply Troubleshooting
This section provides information to help you isolate the problem to the assembly
level when the power system is not operating properly.
There are three main types of faults:
• Under-voltage faults
• Over-temperature faults
• Over-voltage faults
To determine what type of fault is occurring and what assembly needs to be
replaced, follow these steps:
1
Unplug the AC power cord from the rear of the instrument so the +5 V standby
power supply can fully discharge.
2
Wait 30 seconds.
3
Plug the AC power cord back into the oscilloscope.
4
Wait 5 seconds.
5
Press the front panel power button, and count how many seconds it takes for
the oscilloscope to lose power again.
a
If it takes about 2 seconds for the scope to lose power, go to the
“Under-voltage fault” section in this chapter.
b
If it takes 4 seconds or more for the scope to lose power, go to the
“Over-temperature fault” section in this chapter.
c
If the scope never powers up, or shuts off almost immediately, go to the
“Over-voltage fault” section in this chapter.
d
If all the steps within these sections have been followed and the
oscilloscope still does not turn on, go to the “Motherboard verification”
section of this chapter.
WARNING
SHOCK HAZARD! Maintenance should be performed by trained service personnel.
Lack of training and awareness could result in electrical shock or other injury. When
maintenance can be performed without power applied, the power cord should be
removed from the oscilloscope.
WARNING
SHOCK HAZARD! Once the bulk +12 V power supply is removed from the
oscilloscope, two AC leads located on the supply are exposed and severe shock can
result if touched. Extreme care should be taken to avoid contact with these leads
when removing or testing the bulk +12 V power supply.