Universal Serial Bus (USB) port problemsv Follow the suggested actions in the order in which they are listed in the Action column until the problemis solved.v See Chapter 3, “Parts listing, System x3800 Type 8866,” on page 107 to determine which components arecustomer replaceable units (CRU) and which components are field replaceable units (FRU).v If an action step is preceded by “(Trained service technician only),” that step must be performed only by atrained service technician.Symptom ActionA USB device does not work. 1. Run USB diagnostics (see “Running the diagnostic programs” on page 60).2. Make sure that:v The correct USB device driver is installed.v The operating system supports USB devices.v A standard PS/2 keyboard or mouse is not connected to the server. If it is, aUSB keyboard or mouse will not work during POST.3. Make sure that the USB configuration options are set correctly in theConfiguration/Setup Utility program menu (see the User’s Guide for moreinformation).4. If you are using a USB hub, disconnect the USB device from the hub andconnect it directly to the server.Video problemsSee “Monitor problems” on page 44.Light path diagnosticsLight path diagnostics is a system of LEDs on various external and internalcomponents of the server. When an error occurs, LEDs are lit throughout theserver. By viewing the LEDs in a particular order, you can often identify the sourceof the error.The server is designed so that LEDs remain lit when the server is connected to anac power source but is not turned on, provided that the power supply is operatingcorrectly. This feature helps you to isolate the problem when the operating systemis shut down.Any memory, microprocessor, or VRM LED can be lit again without ac power afteryou remove the microprocessor tray so that you can isolate a problem. After acpower has been removed from the server, power remains available to these LEDsfor up to 24 hours.To view the memory, microprocessor, or VRM LEDs, press and hold the light pathdiagnostics button on the memory card or on the microprocessor board briefly tolight the error LEDs.The LEDs that were lit while the server was running will be lit again while the buttonis pressed.Many errors are first indicated by a lit information LED or system-error LED on theoperator information panel on the front of the server. If one or both of these LEDsare lit, one or more LEDs elsewhere in the server might also be lit and can directyou to the source of the error.50 IBM System x3800 Type 8866: Problem Determination and Service Guide
