Keysight 9000 Series Service Manual page 64

Chapter 4: Troubleshooting
How to Use the Power Fault LEDs
Please read the paragraph directly below as it discusses that a fault on one sequencer causes LEDs
corresponding to other sequencers to illuminate. This is important to understand before proceeding so
you know which LED is actually the root of the problem.
When a fault occurs on a given sequencer, it notifies the other two using the Fault signal. The other two
sequencers report this as an External Fault as well. For example, if the first sequencer has an over-voltage
on Channel 1, it will report an External Fault with Channel 1 as the source. The other two sequencers
will report it as an External Fault with the source as Channel 4. Similarly, if the first sequencer has an
under-voltage failure on +12V, it will report a Reset Fault on Channel 1 and the other two sequencers
will report External Faults on Channel 4. As you can see, any fault on one of the sequencers always
reports an External Fault on Channel 4 on the other two sequencers. Look for the fault that is not an
External Fault on Channel 4 as the cause of the shutdown. If all three sequencers report an External
Fault on channel 4, it will take some work to determine the real source. It could be on any of the Channel
4 sources (+2.5V, +1.2V, -3.8V), an over-temperature fault (look for the over-temperature LED to light),
or an FPGA issued fault.
Sequencer 1 Group Faults:
If the fault occurs in the first group of LEDs (Sequencer 1) then the problem is with the 12 V bulk power
supply, the power cables, or the acquisition board. You should check the power cables first, then the
bulk power supply, and finally the acquisition board. Reinstall any power supplies, cables, or acquisition
boards that turned out not to be the problem.
Sequencer 2 or 3 Groups Faults:
If the fault occurs in any of the other groupings (Sequencer 2 or 3) then the problem is most likely the
acquisition board. If replacing the acquisition board does not fix the fault then the power cables may be
causing the problem.
Over Temp LED Fault:
If the Over Temp LED is illuminated then first make sure that nothing is blocking the air flow. There
cannot be anything underneath the oscilloscope (such as a piece of paper) that will block the vents nor
can the oscilloscope rest on anything except a hard, flat surface. Also, there needs to be proper clearance
in the rear of the oscilloscope. If the clearance is adequate then investigate the fans. If one or more are
not turning then there is either a problem with the fan(s) or the fan cables.
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