Dell SE2416h monitor power cycles - very weird behavior

[Ifixstuff9]

Hello all,

I have a dell SE2416h monitor that power cycles at somewhat random intervals. When the monitor is first powered on after being off for a few hours, it lasts 15-30 mins before the first power cycle. After that, the cycles progressively get more frequent until the monitor cycles every few seconds.

I'm not sure what is causing this, but maybe something is overheating, causing the monitor to shut off? That would explain why it gets worse with time.

Now here is where things get weird (at least to me, this might be some some common symptom I've never heard of). After taking the monitor apart and laying it flat on my desk to work on, I noticed that if power supply/logic board assembly (which I will now refer to as just "assembly") is orientated a certain way, the monitor will work fine.

Let me explain as best as I can: with the assembly laying flat on the back of the monitor, and the green part of the circuit board facing the back of the LCD (see picture 1), the monitor will power cycle.

But if I flip over the assembly so that the green part of the circuit boards is facing the ceiling (see pic 2), the monitor will work perfectly fine. Yesterday it ran over 3 hours without power cycling before I shut it off myself, and today it has run for many more this way and has worked fine. And believe me, this isn't a fluke; I have tested this 10+ times today and yesterday and every time, without fail, the monitor will work fine.

For reference, here are voltages from the power supply:

19v - 18.29v
19v - 18.27v

GND - GND
GND - GND

I actually wasn't even able to measure voltages in the monitor while it was power cycling, because as soon as I flipped the assembly to gain access to the test points, the monitor began working fine.

So, is there any explanation for this weird behavior? Any parts that, when bad, exhibit similar symptoms? I'm honestly completely lost right now, because I can't think of any reason why the monitor would act this way.

[petehall347]

check the soldering on the transformer .

[Ifixstuff9]

Will do, what should I look out for? I checked the soldering and everything looks fine, but I might be missing something.

[petehall347]

cold solder joints . am thinking the weight of the transformer is making it connect so it works upside down .

[Ifixstuff9]

Ok, thank you. I'll try reheating the solder joints on the transformer and checking the rest of the board for any suspicious looking solder joints.

[Ifixstuff9]

Quick update, about a week ago I re-soldered some of the solder joints on the power supply. I did an admittedly crappy job because I was rushed, but I was just hoping to get some results.

And results I got, because after that the monitor would only stay on for a minute before powercycling. I basically made the problem much worse, but at least I narrowed things down to a soldering issue (I think). Looks like I finally have some time to work on it tonight, I'll re-solder everything but I'll make sure I do a better job this time. I also finally got more flux, so hopefully my solder joints will be higher quality.

[Davi.p]

Bad solderings or bad contact on PSU>interface bd cable, use the handle of a screwdriver to hit the parts in various points..