Computer won't start/post, despite new PSU/motherboard

Step two: The Opening

When I try to start my computer, the lights and fans come on, but nothing else happens. There are no beeps. After working through troubleshooters, I replaced the motherboard, and the computer worked for a while, but then wouldn’t start again. I replaced the PSU and again, the computer worked for a while, but when switched off it wouldn’t start again.

Step three: History
The problem started a few weeks ago. Sometimes when I tried to start the computer it would take more than one attempt before it got going. As long as it was left on it seemed to be OK, but once switched off it didn’t always start again. There were never any beeps if it wouldn’t start. I tried using a post card, but nothing showed on that.
I don’t remember installing any new hardware or software at the beginning of the problem. (However I had a long-standing problem with the computer sometimes buzzing and freezing, and while the main problem was ongoing, I traced the buzzing problem to the network card (disabling it stopped the problem) and have now removed it.)
I worked through some troubleshooters, and decided that the problem might be the motherboard. Somebody had changed the voltage on the old PSU when I built the computer over a year ago, causing it to break. I wondered if it had also caused some damage to the motherboard which hadn’t been initially apparent. Replacing the motherboard seemed to improve the situation, but soon the same problem was occurring again. I tried replacing the PSU, but still had the same problem.
Now, instead of needing several starts, the computer won’t start at all.

Step four: The Full Story:
When I press the power button the fans and lights come on, but nothing else happens. I can see the CPU fan spinning and the green light on the motherboard. There are no beeps, and nothing on shows on the monitor. There are no error messages.

Step five: The specs
List each one of the parts in your computer. This must be a full list. If some parts are from an older build, this might be important.
CPU Intel Core 2 Duo E7400 2.8GHz Socket 775 1066MHz FSB 3 MB L2 Cache
Motherboard (model number) Asus P5G41c-M LX
RAM (Model number, speed, timings, voltage) Corsair Dominator 2 x 2GB cm2x1024-8500C5D
CPU cooler (stock or not, model if applicable) stock wattage at least)
Hard drive(s) Seagate 250GB and 1 TB
Operating System Windows Windows 7 64 bit
Video Card (model number) Nvidia GeForce G220
Power Supply Corsair TX650
Case (for cooling issues) Casecom. The case is too big for the motherboard, so I can’t attach the front panel with the sound and USB.
ANY other parts. If you have an ipod plugged in, we want to know. Someone else who uses the computer plugs in an ipod, but it hasn’t been plugged in when I’ve used it.

Step six:
I have worked through various guides I have found. I have tried removing the motherboard battery and replacing it, reseating everything, starting with most things disconnected, changing around or removing the RAM, taking the motherboard out of the case, replacing the motherboard and the PSU, checking for anything which looks loose or damaged.

I have worked through the guide here:

1. Did you carefully read the motherboard owners manual? Yes.

2. Did you plug in the 4/8-pin CPU power connector located near the CPU socket? Yes. There were only 4 connections.

3. Did you install the standoffs under the motherboard? I think so. There were only three supplied.

4. Did you verify that the video card is fully seated? Yes, I have tried reseating it many, many times. I ended up breaking the plastic lever at the side.

5. Did you attach all the required power connector(s) to the video card? It doesn’t seem to need a power connector.

6. Have you tried booting with just one stick of RAM installed? Yes. It’s the same as trying with two sticks or none.

7. Did you verify that all memory modules are fully inserted? Yes, I have reinstalled it many times.

8. Did you verify in the owners manual that you're using the correct RAM slots? Yes.

9. Did you remove the plastic guard over the CPU socket? I must have done when I first installed it, as I can’t see any plastic guard.

10. Did you install the CPU correctly? There appears to be only one way to install it, as there is a notch.

11. Are there any bent pins on the motherboard/CPU? Not that I can see.

12. If using an after market CPU cooler, did you get any thermal paste on the motherboard, CPU socket, or CPU pins? I changed to the stock cooler. It came with paste already in place, but after reinstalling it seemed to be wearing off, so I redid it with thermal paste. After reinstalling many times, I did get a speck of thermal paste on the CPU.

13. Is the CPU fan plugged in? Yes.

14. If using a stock cooler, was the thermal material on the base of the cooler free of foreign material, and did you remove any protective covering? If the stock cooler has push-pins, did you ensure that all four pins snapped securely into place? Yes.

15. Are any loose screws laying on the motherboard, or jammed against it? Are there any wires run directly under the motherboard? No.

16. Did you ensure you discharged all static electricity before touching any of your components? Yes.
17. Did you install the system speaker (if provided) so you can check beep-codes in the manual? The connector for the front speaker doesn’t reach as far as its place on the motherboard.

18. Did you read the instructions in the manual on how to properly connect the front panel plugs? Yes. I found it fiddly, but I think it’s correct. I have tried disconnecting the reset switch.

19. Did you turn on the power supply switch located on the back of the PSU? Yes.

20. Is your CPU supported by the BIOS revision installed on your motherboard? I think so.

21. Have you tried resetting the CMOS? Yes.

22. If you have integrated video and a video card, try the integrated video port.

23. Make certain all cables and components including RAM and expansion cards are tight within their sockets. Yes. If I disconnect things, I have no beeps. I have replaced the PSU and motherboard.
Breadboarding - I still have no beeps.

I'm reluctant to keep doing things, as I feel I'm now gradually damaging the computer by fiddling with it.
12 answers Last reply
More about computer start post motherboard
  1. 3 standoffs? Most motherboards have 6 to 9 attaching screws all of them need standoffs from the motherboard tray! Maybe a short is killing of your components slowly!
  2. Thank you for your help. Would buying a new case sort out the problem? Or is the damage already done (I still had the same problem when I took the motherboard out of the case)? What parts are likely to be damaged and need replacing? (Hopefully not the new motherboard :( ).
  3. I can't edit my post above, but I just wanted to add a couple of points:

    - the case with three standoffs is the one that I'd used for over a year without problems, but I don't know if the problem would take a while to develop?
    - I'm not sure what size of case to buy. The one I have seems to be too big (which I thought would make it easier to work in, but it doesn't)
    - After replacing the motherboard, my computer didn't seem to recognise all the RAM. It looked like I had 2GB installed, regardless of whether I installed one or both sticks. I have no idea if that's related to the main problem!
  4. It is possible that your board was faulty from the get go if it only recognized 2 out of 4 modules. I am not familiar with your case so cant really comment on it. Any mid tower case should be sufficient for your rig. Here is one of the more popular budget cases with good cooling properties
  5. Thank you! What would I need to buy as well as a new case? (I'm assuming because the computer won't start even when the motherboard isn't in the case, it won't work just by putting it in a new case). Do I need a new CPU?
  6. Possibility is that your motherboard is dead, usually when it comes down to CPU's or mobo's it is the mobo.
  7. The trouble is that I've already replaced the mobo, because I initially thought that was the problem. However, I still had the same problem with the new one. I'm worried that yet another new one won't make any difference.
  8. Have you tried running the system on the integrated GPU without the GT220 card? Just in case your card is gone bad.
  9. Yes, I tried (plugging the monitor into the back panel, and taking out the GT220 card). I tried using a different monitor too), but it didn't work. I've also tried it without the monitor attached at all and the card removed. I feel I should be getting some sort of beeps when I try to start the computer, but it never seems to get that far, no matter what I remove.
  10. More and more pointing to the motherboard unless it is as simple as the PSU being bad which happens even with quality PSU's.
  11. I'll try another motherboard then.

    If I knew for sure that both the motherboard and the CPU need replacing, I would think about upgrading the computer, but if it was just the motherboard I would look for something that would go with my CPU and RAM. I was thinking about this one or maybe I should spend a few pounds more to buy another of the one I've got.

    Thank you very much for your help.
  12. Yes, it was the motherboard.

    I ended up ordering a new motherboard, but ordered the wrong one. I had also ordered a new CPU in case the old one didn't work (I think I had got a speck of thermal paste on it during one of my many reinstallations and I know that's something that mustn't happen). I tried the new CPU with the old motherboard in the new case, and no joy. I tried the new motherboard and the new CPU in the new case and it worked perfectly. Thank you for pointing me in the right direction. I had kept thinking it couldn't be the mobo because I'd already replaced that.

    Thank you for the recommendation for the case. It was more expensive than I'd planned for my very budget-end system, but it was so much better and easier to work in than my previous case.
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