Intermittent Problems; Undetermined Problems - Lenovo ThinkPad X13 Yoga Gen 4 Hardware Maintenance Manual
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Table 6. LCD-related symptoms
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.
Horizontal or vertical lines displayed on LCD.
Intermittent problems
Intermittent system hang problems might happen due to a variety of causes that have nothing to do with a
hardware defect, such as cosmic radiation, ESD, or software errors. FRU replacement should be considered
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.
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
If the diagnostic tests did not identify the device that has failed, if wrong devices are installed, or if the
system simply is not operating, follow these procedures to isolate the failing FRU (do not isolate FRUs that
have no defects).
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 24.
1. Turn off the computer.
2. Visually check each FRU for damage. Replace any damaged FRU.
3. Remove or disconnect all of the following devices:
a. Non-ThinkPad devices
b. Devices attached to the dock
c. Printer, mouse, and other external devices
d. Battery
e. Solid-state drive
f. External diskette drive or optical drive
g. Memory module
h. PC cards
4. Turn on the computer.
5. Determine whether the problem has been solved.
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 FRUs one at a time (do not replace a nondefective FRU):
a. System board
b. LCD assembly
FRU or action, in sequence
1. Run LCD Self Test.
2. Replace the system board.
1. Reseat the LCD connectors.
2. Replace the LCD assembly.
3. Replace the system board.
1. See important note for "LCD-related symptoms".
2. Reseat all LCD connectors.
3. Replace the LCD assembly.
4. Replace the system board.
Replace the LCD assembly.
Chapter 4
.
Related service information
37
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