It has mainly two reasons. One is the faulty LCD. The other is the problem in the GMCH ( graphic controller chip ). First of all connect an external monitor and check the display. If it is OK, then the problem is in GMCH. Otherwise replace LCD. The GMCH problem can be solved by a technician only. Sometimes it is needed to replace the chip and sometimes just heating up the chip will solve the problem.
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It has mainly two reasons. One is the faulty LCD. The other is the problem in the GMCH ( graphic controller chip ). First of all connect an external monitor and check the display. If it is OK, then the problem is in GMCH. Otherwise replace LCD. The GMCH problem can be solved by a technician only. Sometimes it is needed to replace the chip and sometimes just heating up the chip will solve the problem.