EVGA nForce 780i SLI doesn\'t find graphics card

[tintinmilou]

My home-built PC with an EVGA nForce 780i SLI Motherboard (132-CK-NF78) started freezing. Then, it started failing to boot occasionally, giving me a long beep followed by two short, indicating it cannot locate the graphics card. Now it does it all the time. I tried buying a cheap (EVGA 520) graphics card to see if it was my ASUS EN 9800 GTX+, but I get the same one long and two short beeps. If I try another ePCI slot, the PC finds the graphic card, but doesn't get past the boot, complaining that a single Graphic card must be in slot ePCI-1.
What do you think? A bad south bridge? I haven't tried reseating the CPU yet. I don't think my North and South bridge chips are socketed...

 

[monsta]

Check your ram one of the sticks could be faulty , boot up the pc again with one stick at a time and see if you have any luck.

 

[tintinmilou]

Thanks. I've now tried that, to no effect. I've still got an older power supply, I think my next step is to breadboard, starting with the alternate PS. Some of the threads I've seen indicate that the South Bridge on the EVGA 680i and 780i MBs tends to bad solder connections. As a last resort, I made try the "Easy-Bake oven" approach, or take a heat gun to the underside of the MB where the bridge resides. I get the beeps when it's showing post code 25, the VBIOS / shadow memory, but it goes past it to the FF code, booting, even though it has no video.

 

[tintinmilou]

Well, after bread boarding and trying everything I could think of, I tried the baking solution, with much fear and trepidation. Lo and behold, it worked! I no longer get the post code 25, it boots and runs! At least for now.
I pre-heated my oven to 385 degrees with a flat baking sheet in there. I removed everything from the board, including heat sinks, BIOS chip, battery, etc, and set it in the oven on top of four corks (They proceeded to smoke!) and left it in there for six minutes. I carefully removed it and let it cool a bit before setting it down on a wooden cutting board to cool down. After that, I plugged it in again and it booted!