Intermittent Problems; Undetermined Problems - Lenovo ThinkPad S2 Yoga Gen 7 Hardware Maintenance Manual

• One pixel consists of R, G, B sub-pixels.
LCD Self Test
When you turn on the computer and the LCD goes black, run LCD Self Test to help you determine whether
the LCD functions normally.
To run LCD Self Test:
1. Ensure that the computer is connected to ac power. Then, press the power button for about seven
seconds to turn off the computer.
2. Press Fn, left Ctrl, and the power button at the same time. If the computer displays five solid colors in
sequence across the entire screen, it indicates that the LCD functions normally.
3. The test lasts for about 20 seconds and then exits automatically. You also can press the power button to
exit the test.
Table 5. 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 26.
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L13 Gen 3, L13 Yoga Gen 3, S2 Gen 7, and S2 Yoga Gen 7 Hardware Maintenance Manual
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.