Power Supply Troubleshooting - Keysight 90000 X Series Service Manual

Power Supply Troubleshooting

This section provides information to help you isolate the problem to the assembly level
when the power system is not operating.
There are three main types of faults:
To determine what type of fault is occurring, and what assembly needs to be replaced,
follow these steps:
There are two sets of LEDs on the backplane assembly and one set on each acquisition
assembly. Seeing which of these LEDs are illuminated will help you identify the reason
for the power failure.
W A R N I N G
SHOCK HAZARD!
The maintenance described in this section is performed with power supplied to the
oscilloscope and with the protective covers removed. Only trained service personnel
who are aware of the hazards involved should perform the maintenance. Read the safety
notices at the back of this guide before proceeding. Failure to observe safety precautions
may result in electric shock.
W A R N I N G
SHOCK HAZARD!
Once the bulk +12V 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
+12V power supply.
• Under- voltage faults
• Over- temperature faults
• Over- voltage faults
1 Unplug the oscilloscope so the +5V standby power supply can fully discharge.
2 Wait 30 seconds.
3 Plug the oscilloscope back in.
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. Keep the oscilloscope plugged in when it
loses power.
• If it takes about 2 seconds for the oscilloscope to lose power, you likely have
an under- voltage fault.
• If it takes 4 seconds or more for the oscilloscope to lose power, you likely
have an over- temperature fault.
• If the oscilloscope never powers up, or flickers then shuts off immediately,
you likely have an over- voltage fault or a defective bulk +12V power supply.
Chapter 4: Troubleshooting
Power Supply Troubleshooting
55