134 Chapter 4Intermittent ProblemsIntermittent system hang problems can be caused by a variety of reasons that have nothing to do with ahardware defect, such as: cosmic radiation, electrostatic discharge, or software errors. FRU replacementshould be considered only when a recurring problem exists.When analyzing an intermittent problem, do the following:1. Run the advanced diagnostic test for the system board in loop mode at least 10 times.2. If no error is detected, do not replace any FRU.3. If any error is detected, replace the FRU. Rerun the test to verify that there are no more errors.Undetermined ProblemsThe diagnostic problems does 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 these procedures to isolate the failing FRU (do not isolate non-defective FRU).NOTE: Verify that all attached devices are supported by the computer.NOTE: Verify that the power supply being used at the time of the failure is operating correctly. (See “Power OnIssue” on page 122.):1. Power-off the computer.2. Visually check them for damage. If any problems are found, replace the FRU.3. Remove or disconnect all of the following devices:• Non-Acer devices• Printer, mouse, and other external devices• Battery pack• Hard disk drive• DIMM• CD-ROM/Diskette drive Module• PC Cards4. Power-on the computer.5. Determine if the problem has changed.6. If the problem does not recur, reconnect the removed devices one at a time until you find the failing FRU.7. If the problem remains, replace the following FRU one at a time. Do not replace a non-defective FRU:• System board• LCD assembly
