Computer won't boot with CPU power cable plugged in, fans spin for a couple seco

A few days ago I tried to upgrade my mobo and my RAM. When I hooked everything up and hit the switch on the PSU, the fans and HDD spun up for a few seconds before dieing. The green power light on the MB stayed lit up, but pressing the power button, or holding it, did absolutely nothing.

From that point, I opened up the computer again and tried a few different things, from switching back to my old ram, trying every stick of ram in every slot individually, making sure everything was firmly plugged in and plugged into the correct spot, clearing the CMOS, and everything else that I found suggested on various forums.
With still no success, I finally breadboarded it and plugged everything in outside the case, and voila, it POSTed with the old ram, and gave me a screen telling me what ram and CPU I had, and telling me that my keyboard was unplugged, which it was. Out of curiosity I tried the new ram, which also worked. Plugged in the keyboard and moved into the new MOBO bios, but then shut it off so that I could put everything back in the computer, figuring that I must have just made a mistake before. Tried starting it all again and had the same problem with the fans and HD spinning up before going dead with no image on my screen.

I went through the entire process again, now quite certain that the mobo and the ram are not the culprits. I've gone through each and every cable, connection, and component piece by piece to see what stops it, and come to find out that right now it will only stay on if the 8pin CPU power cable is NOT plugged in, but of course I get nothing on my screen. When I try with the 8pin or a 4pin plugged in, it does the same thing as before.

This leads me to believe that it is my PSU, or maybe the connection on the mobo. So I tried switching back to my old MOBO, but it does the exact same thing, so now I'm pretty sure it is not the MB.

Today I went to the computer store and picked up a new PSU, rated at 750, instead of my old PSU's 650. Plugged everything in, being careful every step of the way, and yet it does the same thing all over again. Tried the new PSU with the old mobo and still the same thing. So no matter what combination of MB and PSU, I have the same issue. The only other thing i can think of is that maybe I screwed up my CPU somehow in the process. I see no bent pins, and was very careful going from one mobo to the other.

I'm wondering if I might have discharged some static into it and messed it up, or if maybe something else could have affected it, because I highly doubt that both my mobos or both the PSUs are faulty. I was literally using the computer the day that I tried to upgrade, and it was running just fine. I will note that I had to transplant my old cpu cooler bracket to the new mobo, and I had a hard time actually getting the cooler connected to the bracket, and had to apply a bit of pressure because I was connected it wrong like a dumbass. So it's possible I pushed too hard down on the CPU.

The more I think about it, the more it seems as if the CPU is to blame, but if so, would it have POSTed at all while out out the case?
I've already dropped $100 on the new PSU that I hadn't planned on buying, and I'd rather not run out and buy a new CPU without being at least reasonably sure. Any help or suggestions would be greatly appreciated. Here's the specs on my system, before and after:

Before:
MB: M4A785TD-M EVO
RAM: G.Skill Ripjaws 2x2gb(4gb) 1333mhz
CPU: AMD Phenom II X4 925 2.8ghz
PSU: Antec 650watt, not modular
Case: Antec 200

After:
MB: Asus Sabertooth AM3+
RAM: G.Skill Sniper 2x4gb (8gb) 1866mhz
PSU: Thermaltake SMART Series 750 Watt ATX Modular

I'd love to find out if there's just a way to make this work with what I have instead of having to buy yet another part. I'm also a little reluctant to buy a CPU and use my old PSU, in case it might have been part of the problem, but it would be nice to be able to return the new PSU and be able to get back that $100.

Again, any and all help is appreciated.
20 answers Last reply
More about computer boot power cable plugged fans spin couple seco
  1. Hmm. Are you sure the motherboard is mounted correctly on the stand-offs? It could be that the MB is shorting to the case.
  2. Quote:
    With still no success, I finally breadboarded it and plugged everything in outside the case, and voila, it POSTed


    It then seems that the mb and cpu is working. Check the riser screws on which you screw the mb into the case. Maybe one of them is causing a short on the bottom of the mb.
  3. Yup, double-check your stand-offs to make sure you do not have misplaced leftovers from your old motherboard shorting out your new motherboard.
  4. this definitely sound like a minor short circuit. have you tried running without a case?
  5. It only posted the first couple of times outside the case, and not doesn't POST at all, even while breadboarded, so the standoffs don't even come into play anymore, but I double checked that as well after reading that in another thread, and all my standoffs were in the right spots. Actually, I didn't have enough standoffs to begin with, so I put them under the corners and under the graphics card, which seemed like where there'd be the most stress. My graphics card is a PNY XLR8 GTX465, which I forgot to include in my original post.
  6. Not breadboard-POSTing anymore with the Thermaltake PSU, Antec PSU or both?
  7. Both, and also tried with both my old MOBO and the new MOBO, no combination of PSU and MOBO work, even breadboarded. That's why I'm leaning towards the cpu, because it's the only piece that isn't getting swapped out.
  8. Otherwise you bent the board to much and possibly created a hairline crack on 1 or more copper tracks.

    Just FYI, the most stress on the board is the 6 holes around the CPU and PCIx as the CPU and chipset expand and contract the board when heating up and cooling down.

    The installation of any motherboard is good practice to use all holes.And Firstly attach the CPU heatsink and then into the case.(Except obviously if you use a backplate type cooler). take care when inserting the 24 pin power connector as the connector is almost allways on the edge and not well supported by risers.
  9. That is a possibility, but I don't think I would have done that to both of the boards, and I was very careful to keep pressure light. Luckily most stuff goes in pretty easily on both my boards, including the 24pin. And I did put the cpu cooler on outside the case, as well as the ram, so I never had to push on those components while it was in the case at all.
  10. OK, lets start over.

    You said the one board worked once outside the case, and now both mobo's and both PSU combos don't work?

    Remember it is "normal" for some mobo's to switch on without the extra 12v CPU power plug. I tested it now on a old P4 mobo and PSU I have lying around. The P4 also does not POST.
    I think this can be tested by removing the CPU and powering on with the 12v CPU plug in. Im fairly certain it will produce the same -'on' but no POST effect.

    Remove the CPU and if it also does this effect. Your CPU is likely dead.
  11. Sounds like lots of touching outside the case, which means away from "occupational grounding" through the computer case or other presumably grounded item. If you were careless, you might have zapped something with static. While components are fairly rugged against ESD once in-system, they are most vulnerable while they are loose.
  12. Then CPU is dead
  13. Okay, just tried everything once more, and had a slight change. My old mobo now does the same thing, even if the 4pin is not plugged in, so it's not staying on no matter what I try. The new one is mostly acting as before, and I tried starting it with the 8pin plugged in, but the CPU not on the MB, and it does the same thing, spinning up fans before dieing.
  14. Well, darn :cry: . Guess it's time to get that 8150 a little earlier than I thought, lol. I wonder of Micro Center will take back the power supply, seeing as both PSUs behave the same, I'm guessing my original still works. This time I'm also gonna get one of those grounding bracelets, like I should have done in the first place. :sweat:

    Thanks for the all the help. I'm gonna do a little shopping and try to get a new cpu as quick as possible, and I'll post back here once I've tried putting it in.
  15. Ask them kindly, to refund. Otherwise keep it ^^.

    To earth yourself you can just touch the metal casing too. Just leave the power cord plugged in.

    Happy Hunting...
  16. blakwidowrsa said:
    To earth yourself you can just touch the metal casing too. Just leave the power cord plugged in.

    With the PSU's hard-switch turned off to avoid accidental turn-on and possible damage from shorting something to 5VSB while (dis)assembling.
  17. InvalidError said:
    With the PSU's hard-switch turned off to avoid accidental turn-on and possible damage from shorting something to 5VSB while (dis)assembling.


    Yes- Static Electricity directly onto electronic part not recommended.
    But you'll never be able to "short" something by only touching an earth.(Except if you are part of the live wire. He-he) Because if power do somehow leak into the earth it will immediately trip the earth-leakage. It's a safety feature in our homes' Power DB's that prevent a live stream from being touched at any time.Think about it, how long ago did you experience the sheer...grip that 240Volt feels like ? ^^ It's .... electrifying. LOL♥
  18. blakwidowrsa said:
    Because if power do somehow leak into the earth it will immediately trip the earth-leakage. It's a safety feature in our homes' Power DB's that prevent a live stream from being touched at any time.Think about it, how long ago did you experience the sheer...grip that 240Volt feels like ? ^^ It's .... electrifying. LOL♥

    The 5VSB, 3.3V, 5V and 12V outputs on the PSU are isolated from the mains via transformers and optical isolators. Any shorts between isolated outputs and their respective local ground are invisible to GFCI breakers because the current return loop never passes through the GFCI.

    Even if the GFCI tripped (which it could if the short involved a separately grounded device), the PSU's primary storage caps would still hold plenty of energy to cause considerable damage before the PSU shuts down.

    There is no way for external fault protection devices to protect electronics against internal shorts. By the time external protections do anything, the damage is already done. All GFCI and AFCI do is protect humans from electrocution and fire hazards, not electronics.
  19. Quote:
    Yes- Static Electricity directly onto electronic part not recommended.
    But you'll never be able to "short" something by only touching an earth.
  20. i realize this was a few years ago but im having the same issues and i just want to make sure that when you replaced the cpu and it worked. Thanks in advance.
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