Computer being picky on video card no post beep possible blown mobo

[moonrider626]

I bought a 560 video card and found that my power sourse only put out 18 amps when it required 20 I called tech support and they assured me that it would work. I plugged it in using a adaptor supplied (four pin) that may have had a fan connected to it. The computer turns on then off, on then off, so I turned it off. I when out and. Bought a beast of a power supply, a xfx pro750 tried again and now no display, I put back in my old video card a MSI 440 and nothing, tried a old 520 and surprisingly that worked. So I returned the 560 and bought a 7750 and a new hydro CPU cooler. Plugged it in and nothing. So I cleaned the PCI slot using air, a eraser tip and finally a tooth pick, to no avail. I tried the 440 and 7750 on my brother's computer and now his computer isn t working. The 440 did work but not the 7750. Which also caused the computer to turn off and on. I checked all.connections and since it still works with the 520 I suppose it isn't the ram.
I3 processor. Low end
8 gigs ram
MSI h61m-p23 (b23) mobo
3 fans
Old tv.card fm1236/f h-5
Xfx pro 750w
Sector 5 ddr3 1333mhz 4 gb x2 PVC38g1333elk

 

[moonrider626]

Forgot to mention the on board graffics work, if I connect a 2nd monitor it works after boot, does not show in devices, video card fan works. Power supply is brand new and old power supply was just fine with 520 was a 500 watt rocketfish rf-500wps2. Please help, I can live with a old video card til I get a mobo if necessary but this has stumpted me and my brother's computer had a 5670 I believe and a 500 watt power supply, now its a no display brick

 

[moonrider626]

Also I have reseated the bios battery mobo and updated bios. Checked to see if onboard video was checked and it s set to the PCI I m not over clocking and miss my skyrim and would hate to explain why I ve messed up another video card to fry's

 

[moonrider626]

Also I have reseated the bios battery mobo and updated bios. Checked to see if onboard video was checked and it s set to the PCI I m not over clocking and miss my skyrim and would hate to explain why I ve messed up another video card to fry'si have uninstalled all drivers using a program mentioned on these forums and reinstalled the 520 drivers automaticly with windows 7 64 bit ultimate edition

 

[moonrider626]

Odd thing is my brother's video card worked in mine, also a Asus 5670 (i believe) after messing up his, he was like try this, I can t use it now

 

[moonrider626]

After some thought the video card that stopped working on my brothers computer and worked on mime was a azus 550 ti.