Lenovo ThinkPad 570 English - Hardware Maintenance Manual for 570 systems - Page 50
Intermittent problems, Undetermined problems, See Power system
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Symptom-to-FRU index Symptom or error No beep, power-on indicator on, and a blank LCD during POST LCD backlight not working LCD too dark LCD brightness cannot be adjusted LCD contrast cannot be adjusted LCD screen unreadable Characters missing pixels Screen abnormal Wrong color displayed LCD has extra horizontal or vertical lines displayed FRU or action, in sequence 1. System board. 1. Reseat the LCD connectors.. 2. LCD assembly. 3. System board. 1. See important note for "LCD-related symptoms." . 2. Reseat all LCD connectors. 3. LCD assembly. 4. System board. 1. LCD assembly. Intermittent problems Intermittent system hang problems can be due to a variety of causes that have nothing to do with a hardware defect, such as: cosmic radiation, electrostatic discharge, or software errors. FRU replacement should be considered only when a recurring problem exists. When analyzing an intermittent problem, do the following: 1. Run the diagnostic test for the system board in loop mode at least 10 times. 2. If no error is detected, do not replace any FRUs. 3. If any error is detected, replace the FRU shown by the FRU code. Rerun the test to verify that no more errors exist. Undetermined problems You are here because the diagnostic tests did not identify which adapter or device failed, installed devices are incorrect, a short circuit is suspected, or the system is inoperative. Follow these procedures to isolate the failing FRU (do not isolate nondefective FRUs). Verify that all attached devices are supported by the computer. Verify that the power supply being used at the time of the failure is operating correctly. (See "Power system checkout" on page 29.) 1. Power off the computer. 2. Visually check each FRU for damage. Replace any damaged FRU. 46 ThinkPad 570 and 570E Hardware Maintenance Manual