Lenovo ThinkPad T520 Hardware Maintenance Manual

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Contents

No-beep symptomsTable 5. No-beep symptomsSymptom or error FRU or action, in sequenceNo beep, power-on indicator on, LCD blank, and noPOST.1. Make sure that every connector is connectedtightly and correctly.2. DIMM3. System boardNo beep, power-on indicator on, and LCD blank duringPOST.1. Reseat DIMM.2. System boardThe power-on password prompt appears. A power-on password or a supervisor password is set.Type the password and press Enter.The hard-disk password prompt appears. A hard-disk password is set. Type the password andpress Enter.LCD-related symptomsImportant: The TFT LCD for the notebook computer contains many thin-film transistors (TFTs). Thepresence of a small number of dots that are missing, discolored, or always lighted is characteristic of TFTLCD technology, but excessive pixel problems can cause viewing concerns.If the LCD you are servicing hastwo or less visible defective pixels, it should not be considered faulty. However, if the LCD has three or morevisible defective pixels, it will be deemed as defective by Lenovo and it should be replaced.Note:• This policy applies to all ThinkPad Notebooks purchased on 1 January, 2008 or later.• Lenovo will not provide replacement if the LCD is within specification as we cannot guarantee thatany replacement LCD will have zero pixel defects.• One pixel consists of R, G, B sub-pixels.Table 6. LCD-related symptomsSymptom or error FRU or action, in sequenceNo beep, power-on indicator on, and a blank LCD duringPOST.System board• LCD backlight not working• LCD too dark• LCD brightness cannot be adjusted.• LCD contrast cannot be adjusted.1. Reseat the LCD connectors.2. LCD assembly3. System board• LCD screen unreadable• Characters missing pixels• Screen abnormal• Wrong color displayed1. See important note for “LCD-related symptoms.”2. Reseat all LCD connectors.3. LCD assembly4. System boardHorizontal or vertical lines displayed on LCD LCD assemblyIntermittent problemsIntermittent system hang problems can be due to a variety of causes that have nothing to do with a hardwaredefect, such as cosmic radiation, electrostatic discharge, or software errors. FRU replacement should beconsidered only when a problem recurs.When analyzing an intermittent problem, do the following:1. Run the diagnostic test for the system board in loop mode at least 10 times.Chapter 4. Related service information 43