Dead Dell Desktop motherboards

[guyman70718]

Hey there, I was wondering if anyone here could help me with 2 dell motherboards with the same symptoms that I have now collecting dust. Basically, I used to use a Dell Inspiron 3647 as a server and I had a kit of 16gb of ram from crucial installed. A few months ago, I realized that the thing was shut off for some reason, and I went to turn it on. Pressing the power button would make it come on for a second then go off. Replaced the power supply and same issue. I just declared it dead and sacrificed it for parts, as I had another dell I could use. I put the ram into a Dell 660s I had laying around and set it up, and it was working fine for about a day, when that PC shut off and started doing the exact same thing. Replaced PSU, reset CMOS and nothing changed. I tried resetting the CMOS on the original 3647 and now the power light doesn't come on at all when I press it, and no fan spin either. If I press the power supply self test button the cpu fan spins up to max speed and that's the only life I can get from the pc. I do have one more PC that I am now using as the server, but not with that ram anymore (duh) but now I am interested in trying to repair at least one of the motherboards as board repair practice.

I do have a little SMD soldering experience, for example the third dell needed its BIOS chip replaced, but I don't know where to start to try diagnosing the board. I checked the caps and none are leaking or bulging as far as I can tell (both boards are about only 5 years old anyway), and that's really all I know how to do. I don't need to be spoonfed the answer, but it seems that most desktop motherboards aren't worth repairing to most people, so as a result there isn't much information on where to start. If anyone has any ideas, I am interested in hearing them.

[guyman70718]

So, I made a little progress today looking at one of the computers. I checked the capacitors around the SuperIO chip for shorts and found none. I also checked around the chipset for shorts and found a few, but then I checked the working board and I also found a few so I'm just going to assume that my multimeter just isn't sensitive enough. (it is a fluke 73 series ii) I held down the power supply's self test button to see if it made any chips heat up and I found the chipset started getting pretty warm when I was pressing it, so I am starting to wonder if the chipset is bad (and this is a lost cause).