Dell U2718Q, horizontal lines. second opinion welcome

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  • vulubalulu
    New Member
    • Jun 2023
    • 8
    • Atlantis

    #1

    Dell U2718Q, horizontal lines. second opinion welcome

    I have never seen an issue such as this one. horizontal lines across the monitor in a consistent manner. I am really interested to get to the bottom of this and I'd value any input from the community.
    There are three separate PCB parts attached to each other. They function as SMPS, backlight driver and main board.
    I checked the all three blue PCBs: SMPS outputs 19V, PWM controller + mosfets without anomalies, main board has 3V, 5V, 10.5V and 19V present. Crystals output the right clockspeed. This is to be expected as the monitor turns on.
    I haven't explored at the green PCB (TCON board?) too much as there is an IC malfunctioning. Once it reaches 150, somewhere a safety mechanism is triggered and the monitor image 'restarts'. (think degaussing CRT monitors). The longer i let it run the more frequent it restarts. Putting a thermal pad on the IC stops it from restarting. There are two more transistors that get very hot, I am guessing that the SiW ic is heating up the other.
    There is no datasheet I could find but I took a couple measurements and what stood out to me are the waveforms of the 8 clk pins. 1-6 look normal and 7 and 8 are outliers. This is my first week owning an oscilloscope, I have no clue how to interpret it. I have already ordered a replacement chip in hopes that it will fix this issue. What else can I do here?
    It doesn't feel right that a bad clk signal can cause this much heat, can't find any shorts around SiW though.
    Last edited by vulubalulu; 08-14-2024, 03:13 PM.

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