Question about Samsung SyncMaster 940N Flat panel Monitor

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Samsung Synchmaster 940N fault

Hi, My Samsung Synchmaster 940N has a problem same as one you recently dealt with. It only comes on for about 2 secs and then goes off. When you press the blue on/off button back on, it comes on again for two secs and then goes off and so on.

I notice that you had a query the same, do you know what that fellow ended up doing with it. Mine is barely 12months old. I bought it new off Ebay and notice that Samsung do not give warranties for auctioned items.

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  • afmutw Nov 07, 2008

    I have exactly the same problem. Did you find a solution? Did you find the backlight inverter?



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I've had the same problem with mine and just fixed it (well, it's still working now, so fingers crossed).

The problem is the high-voltage supply to the backlight is breaking down due to a discharge path somewhere.

I took my monitor apart and noticed there was a lot of residue on the underside (surface-mount) side of the power supply board. The residue was bad enough to see fingerprints in it from the assembly workers. I cleaned the board thoroughly with isopropanol (other flux solvents would probably do a similar job) let it dry thoroughly, reassembled it and since then I've no problems :o)

The monitor isn't easy to take apart. Unplug the mains supply and video connector and remove the three screws and the stand. The body of the monitor is held together with clips all the way around. Prize these apart with a penknife or similar item. You have to be fairly firm, but careful not to slip and damage the monitor or yourself. Once the back is off keep the LCD face down in the front bezel, You'll see a small cable carrying signals from the front panel buttons. Remove the tape holding the cable down and unplug the connector on the end by holding down the latch.

There's a thin shiny panel clipped to the side of the pressed metal covering for the power supply. Prize away the clips on the outer edge first, then you are able to swing the panel towards you and unclip it from the other two locations by the arrows. Underneath are the backlight connectors. Note the colours of the wires (blue near the top, pink near the bottom for both pairs) and unplug them, holding down the latch. The only remaining anchor for the panel is the flat cable connector going to the LCD driver board at the top. Angle the metal pressing up a little so you can reach the connector and press in the two latches at the side. Then just slide the connector out.

Now you can remove the pressed panel holding the power supply and the VGA connector board. Undo the screws and take out the power supply board. Disconnect it from the other board (remember the latch) and pop out the three pegs holding the supplementary insulation sheet onto the back of the board. Don't lever them from the caps, just press the latching ends inwards and they pull out easily. Now your board is free you can inspect it and give it a clean. If anything looks damaged on the board it's probably best to replace it. Otherwise if it's covered in sticky residue like mine, clean it using a clean stippling brush or and old dry toothbrush with plenty of solvent and let it dry for a while.

Reassembly is just the reverse of assembly.

Hope I didn't forget anything. Good luck if you want to try it, but if you're not confident with electronics find someone who is. There are probably a number of faults that could result in this symptom, and I don't know how common mine is.


Posted on Nov 08, 2008

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Go & buy new backlight inverter. change your inverter.

Posted on Oct 19, 2008


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