Keysight 9000 Series Service Manual page 61

Chapter 4: Troubleshooting
How to Use the Power
Fault LEDs
How to Use the Power Fault LEDs
The previous page showed where to look through the rear fan slots to see the upper right corner of the
acquisition board. A series of 13 LEDs is separated into three sections of four LEDs each, with the Over
Temperature LED by itself at the bottom (as shown in Figure 6).
Figure 6
By looking at the pattern of LEDs illuminated after a power failure, you can determine the cause of the
fault. However, in most cases, only assembly level repair is required which greatly simplifies decoding
these LEDs. An in-depth discussion of this LEDs will first be presented so you understand how they
operate and then the assembly level repair procedures will be discussed.
The LEDs must be interpreted in groups of four (as shown in the layout above) with the upper two LEDs
in each group indicating the type of failure and the lower two LEDs indicating the source of the failure.
If a shutdown occurs, use the following table to decode the upper two LEDs (LEDs 1 and 2) in each
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