A system of light emitting diodes (LEDs) is used to convey the results from light path diagnostics.
Light path diagnostics is a system of LEDs on various external and internal components of the server. When an error occurs, LEDs are lit throughout the server. By viewing the LEDs in a particular order, you can often identify the source of the error.
The server is designed so that LEDs remain lit when the server is connected to an ac power source but is not turned on, provided the power supply is operating correctly. This feature helps you to isolate the problem when the operating system is shut down.
Any memory card LED can be lit while the memory card is removed from the server so that you can isolate a problem. After ac power is removed from the server, power remains available to these LEDs for up to 24 hours.
To view the memory card LEDs, press and hold the light path diagnostics button on the memory card to light the error LEDs. The LEDs that were lit while the server was turned on are lit again while the button is pressed.
Many errors are first indicated by a lit information LED or system-error LED on the operator information panel on the front of the server. If one or both of these LEDs are lit, one or more LEDs elsewhere in the server might also be lit and can direct you to the source of the error.
If an error occurs, view the LEDs in the following order:
- Check the operator information panel on the front of the server.
- If the information LED is lit, it indicates that information about a suboptimal condition in the server is available from the baseboard management controller in the system-event log and the IMM event log. Proceed to step 2.
- If the system-error LED is lit, a system error occurred. Go to step 2.
Figure 1. Operator information panel
- To view the light path diagnostics
panel, press the release latch on the front of the operator information
panel to the left, then slide it forward. This reveals the light path
diagnostics panel. Lit LEDs on this panel indicate the type of error
that occurred. Figure 2. Server light path diagnostics panel
- NMI button
- The NMI button is reserved for trained IBM service technicians, who use it to debug the operating system. Pressing the button sends a non-maskable interrupt to the microprocessor, causing the server to reset.
- Reset button
- The reset button is in the lower-right corner of the light path diagnostics panel. Press it to reset the server and run the power-on self-test (POST). You might have to use a pen or the end of a straightened paper clip to press the button.
- Remind button
- You can use the remind button on the light path diagnostics panel
to put the system-error LED on the operator information panel into
Remind mode. When you press the remind button, you acknowledge the
error but indicate that you are not taking immediate action. The system-error
LED flashes while it is in Remind mode and stays in Remind mode until
one of the following conditions occurs:
- All known errors or suboptimal conditions are corrected.
- The server is powered back on.
- A new error or suboptimal condition occurs, causing the system-error LED to be lit again.
- Checkpoint display
- The checkpoint display, indicated by 88 on the light path diagnostic panel, provides checkpoint codes. Checkpoint codes are not error codes; they identify firmware checks when the server stops. There are field-programmable gate array (FPGA) hardware checkpoint codes and basic input/output system checkpoint codes. For more information, see the IBM System x3850 M2 (7141, 7144) Checkpoint listing web page. For a list of checkpoint codes, see Checkpoint codes.
- System service label
- The system service label on the top of the server provides an overview of internal components that correspond to the LEDs on the light path diagnostics panel. This information and the information in Troubleshooting with light path diagnostics for the TS7650 Appliance or TS7650G (Gateway), ProtecTIER V3.3.6 can often provide enough information to correct the error.
- Remove the server cover and look inside the server for lit LEDs. Certain components inside the server have LEDs that are lit to indicate the location of a problem. See the IBM® System x3850 X5 and x3950 X5 Types 7145, 7146, 7143, and 7191 Problem Determination and Service Guide.