Computer turns on, but monitor, mouse, and keyboard don't turn on.

[theamazingpinoy]

I have a custom built gaming computer that I put together a year ago and now I'm having a major issue. At first, my sound wouldn't work when connected to the computer. Then the computer would have issues restarting. The final and most recent incident was when I powered up the computer, the monitor, mouse, and keyboard would have no response like it normally did. I'm somewhat computer techy, so I took out the gpu, ram, and disconnected all the cables and whatnot. I read other forums saying it might be the mobo might be fried, but I can't see any burnt or bulging capacitors on the mobo. I also moved the gpu and ram into other slots to see if that would help, but nothing. I made sure all the contacts were clean and all the proper cables were plugged in. To give some more detail, the fans in my computer are still spinning, and the fan is still spinning. I think the hard drive is still working, because the hd light still flickers. After 2 failed attempts and countless hours spends, I'm totally puzzled on what's wrong.
Computer specs
CPU: amd phenom II x4 955 (3.2 ghz)
GPU: xfx radeon hd 6850
RAM: corsair xms3 ddr3 4gb
PSU: blackstone rx-700ac (700w - set at 115 in the back)
CPU cooler: cooler master v8
Mobo: msi 870a-g54
Hard drive: seagate barracuda 1tb (my main hard drive is broken, using 1tb ATM)

 

[Twoboxer]

. . . At first, my sound wouldn't work when connected to the computer. Then the computer would have issues restarting.
. . .
PSU: blackstone rx-700ac (700w - set at 115 in the back)

Can't be certain exactly what issues you had before - pretty vague description - but you're going to want to buy/borrow a quality psu, swap it in, and see if that solves the problem.

 

[wa1]

Have you tried running just with 1 stick of RAM?

 

[italiasian]

i havent been able to use my desktop for 6 months due to the same problem, i am using my old laptop. I think it is my motherboard, i am not going to buy a replacement untill i can afford to upgrade the whole system.

 

[theamazingpinoy]

Yes I have tried to boot with one stick of ram with no luck.