(Sorry for writing in English, please respond in Russian, I understand but I can't write in Russian.)

The laptop came with a problem no power on. Some voltages were missing, removed 3v3 coil, there was lower resistance there, injected voltage and found shorted HDMI level shift IC - it was hot, PS8101 (U5750). Removed the IC.
All voltages are within tolerance now, board starts when plugged in, the fan spins few seconds, then stops. The led stripe where the power button is (and other led info - wifi, volume etc.) does it's "light show" as it is supposed to do. After approximately 10 seconds, reset signal appears and everything starts again.
The processor gets well heated up, also the PCH BD82HM67 SLGZR (I think not more than it is supposed to). Coils for processor voltages also. The board is UMA, so no nVidia chip. I'm not leaving the board for longer than 4-5 restarts, to avoid overheat.
The IC for generating 3v3 and 5v is (by schematic) TPS51125, on the board was EM FA (RT8205LGQW). I know that they are the same, but just for the sake of it I replaced with a known good TPS from a MacBook board, no result. Interestingly, when I touch the IC with finger, it suddenly makes a hissing noise (maybe coming from some place other on the board), processor voltages go to 0, but TPS stil producess 3v3 and 5v, and gets heated up enormously. After reconnecting the charger, the same cyclic restart are back again. This doesn't happen when TPS is touched with insulator. I don't know whether this should be considered as normal.
There are no obvious shorts anywhere. I tried the board with few known good RAM sticks, three different processors i3, i5, all the same.
Removed the LAN chip that is on the daughter board, same thing.
Reflashed both SPI roms with supposedly good bin files.
I think KBC is OK, it reacts on button, tries to start again when pressed, but it does not go off when holding for 4 seconds.

My theory - if something came through HDMI level shifter, is it possible that it ended up in the PCHand burned it down?!
Should I consider PCH replacement (which is difficult for me due to not having proper equipment for such BGA job) or new motherboard, because it is $40 max, maybe even cheaper than replacing the PCH because other problems may appear?!
I base my assumption on this topic: viewtopic.php?f=41&t=58003

Any help will be greatly appreciated.