23 September 2021

REPAIR: Embedded DisplayPort (eDP) LCD Driver

As luck would have it another item was added to my repair que. This time it was my somewhat "sentimental" secondary monitor, which is basically a recycled ThinkPad X260 display

I really loved this thing as it let me have a 1.5 monitor setup, which was super useful for running Altium. So I knew I had to get it repaired ASAP

Identifying the root cause did not take too long. It turned out that the ACDC adapter failed and managed to feed way more than 12V into the eDP driver board, which eventually fried the 12V to 5V switching regulator. Interestingly all this happened over 3 days, as on the first day I noticed a strange smell in the house but could not pin point it's location, on the second day I noticed the screen flickering, and on the third the screen flashed moments before a bunch of magic smoke was released from the eDP driver D:

The 5V regulator and it's footprint was way beyond salvaging, like the FR4 underneath was charred enough to bulge up. So I cleaned up the pads the best I could, measured the typical current draw on the 5V rail, and finally replaced the section altogether with an adequately rated 5V regulator I had lying around. Also I decided to leave the bulk capacitors and feed in the 5V via original inductor to lower the ripple voltage and current

Other Info

The following might be useful to someone:

  • FC3D6T was the faulty 5V, this is a SOT23-6 package
  • 5V rail drew
    • ~350mA when monitor was ON
    • ~23mA when monitor was OFF
  • 12V rail drew
    • ~210mA when monitor was ON
    • ~12mA when monitor was OFF
  • eDP driver is RTD2556_eDP_WS_R10.1 which also goes by
    • B116XAN02
    • M125NWR3
    • LP133WH1-SPB1
    • LP140WH2-TP
    • N156BGE-EA1
    • M06VH00WX2P33Y00001
    • S20180122-1

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