Diagnosis of a Bad Mobo

Hey tomshardware community, I'm in need of some dire help. A little while back, about 4 weeks or so, my computer crashed, and wouldn't boot up or post BIOS at all, I tested some parts, sent out the mobo for repair, it came back and everything worked well for about 5 days or so.

Now, I'm having similar, but not exactly the same problems. Let me tell you what I've done to diagnose my problem.

1. I've tested the PSU with a PSU tester and all lines are giving out a voltage within their respective tolerances.

2. Reset the CMOS battery.

3. I've taken the motherboard out of the case, taken off the memory, bootable drive, DVD drive, and GPU, put it on an anti-static surface, and plugged in the 24 pin mother board power, and the 8 pin CPU power, and jump started it. The fans on the PSU, the fan on the HSF all spin, and the mobo beeps at me telling me it needs memory. This usually works the 1st time.

Issue: While I'm putting in parts 1 piece at a time, the computer will decide to not turn on. For example, in between RAM stick 1 and 2 it won't turn on, meaning that the little green LED on my mobo labbled "SB_PWR" will light up, but the PSU fan and HSF will not spin nor will any other regular LEDs go on. If I go back to 1 stick of RAM it still won't turn on. If I go back to just HSF and CPU it won't turn on. If I wait an hour and try again, it will most times turn on, and then not boot after I put my GPU into the PCIe slot. So it fails at random stages, but the PSU checks out. Since it at least turns on, it's safe to say that the CPU isn't entirely dead, but maybe damage (i.e. bad die(s)) or the mobo is still damaged.

What do the experts say?

OS: Win7
CPU: core i5 750
GPU: GTX 470
RAM: (2x2) 4GB of 1600Mhz G.Skillz Ripjaw
Motherboard: ASUS P7P55D PRO
PSU: Corsair 750TX

Thanks for the help!
10 answers Last reply Best Answer
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  1. Jeez. You've got yourself a nice one here.
    Wait, what do you mean by "putting in parts one at a time"? You're not trying to put in parts after spinning up the fans, are you? That'll mess up anyone's boot. I hope that's not what you're doing - your graphics card sentence also makes it sound like you've put in the part after it's booted.
    Yes, the CPU could be an issue.
  2. I hope you are unplugging your psu before installing your parts. Install everything then plug your psu in and see if it boot.
  3. Yeah guys, sorry for the confusing post. After every part, I shut off the PSU until the mobo's green LED, labeled sb_pwr, shuts off, then I install the parts. I don't unplug it however. Didn't ever know that I had to do that.
  4. Best answer
    They say you should do that to be safe, but it's not essential.
    Well, seems like the mobo repair just didn't catch the problem.
    Do you have a friend with a spare motherboard that you can breadboard to try out your parts? This could rule out things like a fried CPU.
  5. Yeah, everyone seems to be suggesting that, unfortunately not one with an 1156 socket :(
  6. Can you just RMA? Is it too late or something?
  7. Yeah, it's 1 year old and I purchased them from which doesn't allow a RMA past 30 days of purchase, so I'll just get everything repaired :(

    Thanks for the help though!
  8. Best answer selected by Scooter92.
  9. I think it's pretty difficult to find a physical problem in a mobo, let alone actually fix it, but what do I know. Good luck.
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