Samsung S22a100n monitor repair.

[Refrigerator]

The other day i stumbled upon a rather recent monitor in the dumpster and thought to myself that it would be just a quick cap change on the PSU to get it working again, but i was wrong.
Firstly, this monitor has an external PSU, which i do not have, althogh it did rig a couple wires up to the board for power, so there must be something else wrong.
At first i tried to give it power, but with no success, i thought that the main board was dead, that was untill it gave away some light and a "no signal" image for about a second and then died again.
I then pulled out my DIY RF detector to probe the crystal and the results were rather interesting.
It seems like the crystal is off untill i press the on button and it starts pulsing on and off in about one second intervals, then if i press the on button again at the right time the crystal activity jumps up for a couple seconds and the monitor powers up for about one second and dies.
Not sure what it could be, maybe the internal DC-DC is faulty, but then it wouldn't work at all if that was the case, the processor seems allright, i had it plugged into my PC and had a glimpse of my desktop for a second till the monitor died.
I'll try to get a more graphical representation of the crystal activity tomorrow.
Thanks.

[tautech]

Despite it using an external PSU there will likely be an internal SMPS that could be shutting down from an over-current condition.

Bad caps is the normal cause.

[Shock]

Had a quick look see if this is the correct buck converter. It looks something like that from the layout of components I can see to the right of the IC.

You want to test the supply input and output (does the input or output ever go down?), test components around it, check ripple, isolate it and put a load on it if you have to, if it looks flaky double check what the IC is and replace it. Hot and cold testing is also a good idea.