IBM 2621421 Hardware Maintenance Manual - Page 139

Modem-Related Symptoms Symptom/Error FRU/Action in Sequence Internal modem does not work correctly Go to "Modem Board Check" on page 117. Modem connector Modem board System board Intermittent Problems Intermittent system hang problems can be caused by a variety of reasons that have nothing to do with a hardware defect, such as cosmic radiation, electronic discharge, or software errors. FRU replacement should only be considered when a recurring problem exists. When analyzing the intermittent problem, do the following: 1. Run the diagnostic test for the system board at least 10 times. 2. If no error is detected, do not replace any FRUs. 3. If any error is detected, replace the FRU. Rerun the test to verify that there are no more errors. Undetermined Problems The diagnostic tests did not identify which adapter or device failed, which installed devices are incorrect, whether a short circuit is suspected, or whether the system is inoperative. Follow the procedures below to isolate the failing FRU. Verify that the power supply being used at the time of the failure is operating correctly. 1. Power off the computer. 2. Check the cables, wires, and connectors for short circuits and open circuits. Visually check them for damage. If any problems are found, replace the FRU. 3. Remove or disconnect all of the following devices: Non-IBM devices Printer, external mouse & keyboard, and other external devices Battery pack Hard disk drive Diskette drive/CD-ROM/DVD-ROM drive PC Card (PCMCIA) 4. Power on the computer. 5. Determine if the problem has changed. 6. If the problem does not occur again, reconnect the removed devices one at a time until you find the failing FRU. ThinkPad i Series 1400 (Part II) 131