S27A950D Will not power on and no status light Repair

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S27A950D Will not power on and no status light Repair
Device Samsung SyncMaster SA950
Affects part(s) Logic Board
Needs equipment multimeter, soldering iron, soldering station
Difficulty ◉◉◉◌ Hard
Type Soldering


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Problem description

Model: S27A950D

Board Code: BN41-01668

Won't power on. Status led does not illuminate when plugged in.

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Symptoms

  • Won't power on.
  • Status led does not illuminate when plugged in.

Solution

  • Check the power rails. On the bottom of the board there are test points. 3.3 and 1.26 must be present for the status display to illuminate.
  • There are two buck converters near the power input. These are driven by the Z1033AI ICs "IC204" and "IC202". On my board the 1.26 supply IC was not working and had to be replaced.

If you inject voltage to this circuit, it should draw about 5mA with the device off. When the device is powered on the supply will draw 400-500 mA. After injecting 1.26v the button panel lights up. There is also a fuse "F202" on the output of the 1.26 supply, check this if you have power on the output but the panel still doesn't light up.

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