Mr Customer states his PC displayed “matrix” lines on the monitor. we suspect that the problem would be caused by either spoilt HDMI cable, monitor, external graphic card or board.
we test the PC to verify the symptoms with known good monitor and found out that its true. we noticed that it happens when the display is connected to the external graphic card. we tried using known good cable and the issue persists. the customer need to send in his PC for troubleshooting.
First we removed the graphic card and tested with a known good graphic card and see if the problem remains. the problem is solved, the graphic card shown below is spoilt.
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We run stress test overnight to make sure the problem do not happen again after a long run. the PC passed the test and the display was fine.