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Procedure 5
Replacement Check
The FL unit, FL inverter board, LCD module, and system board are connected to the display
circuits. Any of these components may be damaged. Refer to Chapter 4 for instructions on
how to disassemble the computer and then perform the following checks.
If the FL unit does not light, perform Check 1.
If characters are not displayed clearly, perform Check 3.
If some screen functions do not operate properly, perform Check 3.
If the FL unit remains lit when the display is closed, perform Check 4.
Check 1
Replace the FL unit with a new one and test the display again. If the problem still
exists, perform Check 2.
Check 2
Replace the FL inverter board with a new one and test the display again. If the
problem still exists, perform Check 3.
Check 3
Replace the LCD module with a new one and test the display again. If the
problem still exists, perform Check 4.
Check 4
Replace the display switch with a new one and test the display again. If the
problem still exists, perform Check 5.
Check 5
Replace the display cable with a new one and test the display again. If the
problem still exists, perform Check 6.
Check 6
The upper system board may be damaged. Replace the upper system board with a
new one and test the display again. If the problem still exists, perform Check 7.
Check 7
Replace the lower system board with a new one.
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T4850CT
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