v Follow the suggested actions in the order in which they are listed in the Action column until the problemis solved.v See Chapter 4, “Parts listing, Types 4255, 7945, and 7949 server,” on page 157 to determine whichcomponents are customer 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.v Go to the IBM support Web site at http://www.ibm.com/systems/support/ to check for technicalinformation, hints, tips, and new device drivers or to submit a request for information.Symptom ActionThe server unexpectedly shutsdown, and the LEDs on theoperator information panel arenot lit.See “Solving undetermined problems” on page 154.Serial device problemsv Follow the suggested actions in the order in which they are listed in the Action column until the problemis solved.v See Chapter 4, “Parts listing, Types 4255, 7945, and 7949 server,” on page 157 to determine whichcomponents are customer 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.v Go to the IBM support Web site at http://www.ibm.com/systems/support/ to check for technicalinformation, hints, tips, and new device drivers or to submit a request for information.Symptom ActionThe number of serial ports thatare identified by the operatingsystem is less than the numberof installed serial ports.1. Make sure that:v Each port is assigned a unique address in the Setup utility and none of theserial ports is disabled.v The serial-port adapter (if one is present) is seated correctly.2. Reseat the serial port adapter, if one is present.3. Replace the serial port adapter, if one is present.A serial device does not work. 1. Make sure that:v The device is compatible with the server.v The serial port is enabled and is assigned a unique address.v The device is connected to the correct connector (see “Rear view” on page12).2. Reseat the following components:a. Failing serial deviceb. Serial cable3. Replace the following components one at a time, in the order shown, restartingthe server each time:a. Failing serial deviceb. Serial cablec. (Trained service technician only) System boardChapter 3. Diagnostics 59
