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PC turns on without CPU 4 pin plugged in.

Discussion in 'Motherboards & Memory' started by AphexDreamer, Jun 13, 2011.

  1. AphexDreamer

    AphexDreamer

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    PC turns on without CPU 4 pin plugged in. (Solved)

    With it plugged in the Blue Power LED and fans turns on for a second then turn off.

    Its my uncles HP Pavillion a250n.

    I've replaced the power supply with a new one, I've checked the MotherBoards battery (Its good), I've reseated and applied fresh thermal paste to the cpu and I've tired running the MB with nothing else connected to the PSU. I make sure the CPU fan is plugged in at all times.

    All in all the only way the PC will turn and stay on is if I don't plug in the 4 Pin to the MB which Obiviously I need to get it to boot.

    I'm not sure what it is? Perhaps a shortage somewhere? Should I just take everything out and put it back in?


    From what he has told me, its been running fine, then one day after he shut it down, it just wouldn't turn on.

    Ideas?
     
    Last edited: Jun 14, 2011
  2. erocker

    erocker Super Moderator Staff Member

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    Flip the plug around where it connects to the motherboard for the power button.
     
  3. AphexDreamer

    AphexDreamer

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    You mean the Jumper area?
     
  4. Dbiggs9

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    When i had a pc do this i replaced the PSU same issue, turned out to be the Video card
     
  5. AphexDreamer

    AphexDreamer

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    I took out all Cards... Including the Video card it had. Its just the MB.

    Quick update. Its doing the same thing now with or without the 4 Pin Plugged in o_O?
    That is a split second power up and then off again.
     
  6. temp02 New Member

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    I don't want to sound like I'm bashing ASUS or anything, but all ASUS motherboards I've come in contact with tend to do that from time to time, and then for no reason at all they work again, never found out the reason for this behavior (my best guess is some kind static charge build up somewhere on the board).
    If you can make it work again, please do post what you did, good luck.
     
  7. hellrazor

    hellrazor

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    Going off of temp02, I'd say turn off the PSU, hold down the power button, and then go at it again (after turning the PSU back on).
     
  8. JrRacinFan

    JrRacinFan Served 5k and counting ...

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    Try a hsf research, if that doesn't work disconnect power supply completely from mobo and remove battery leaving it sit for a day. Report back if that doesn't work for you.
     
  9. qubit

    qubit Overclocked quantum bit

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    Aphex, it looks like you've done some quite thorough troubleshooting already, which makes it so much nicer to help you. :toast:

    I'd say the only things that could possibly be doing this now are the mobo, CPU & RAM, in that order. The mobo being by far the most likely culprit. Have a look and see if you can spot any dodgy looking capacitors, especially around the power circuitry. Typical telltales are bulges and leaking goo from them.

    The CPU? Yup: a few years ago, my friend's PC wouldn't access floppy drives properly (remember them?) It just gave errors and was very intermittent, but everything else worked fine. However, the floppy drive worked fine when he swapped out the CPU and failed again when he swapped it back in.

    He ended up calling Intel customer support and they confirmed that the CPU was faulty. Weird, huh? :eek: I would have never guessed the CPU either. I think it was a Pentium 3.
     
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  10. 95Viper

    95Viper

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    Why did you even bring up ASUS and bash them? I've had ASUS boards and none ever did that, so it is not all. The HP Pavillion a250n uses a MSI motherboard anyway.
    And, by coincidence, my latest MSI board did just the same thing and it was the PSU causing it.

    AphexDreamer stated it was; and, I quote:
    HP Desktop PCs - Motherboard Specifications

    HP Pavillion a250n key specifications

    Back to the topic...

    It is just a thought.
    Sounds like it could be the PSU's power good signal.
    Power Good Signal
    How PC Power Supplies Work
    What PSU did you use?

    Edit:

    :toast:

    To add to this:
    1. Un-plug the PSU from the wall socket
    2. Turn-off PSU
    3. Remove the CMOS button battery
    4. Hold down power button for 10+ seconds
    Then, re-install the battery, plug in the PSU, turn on the power button.
    Cross fingers on the right hand:rolleyes: and start up the system.

    @ Qubit> Yes, I saw that, however, even a new PSU can be faulty. As, I just RMAed one I got from Newegg. The 5 volt rail was only pushing 4.19 volts and the System would go into a re-boot loop. So, I replaced it with another and she is fine and dandy. CM is sending a replacement for the faulty one.;)
     
    Last edited: Jun 14, 2011
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  11. qubit

    qubit Overclocked quantum bit

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    @95Viper: Aphex said that he swapped out the PSU in his OP, so it's unlikely to be that.
     
  12. AphexDreamer

    AphexDreamer

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    I've done that same thing time after time. Quick on/sudden off.

    I can try this.

    I've test the board without any ram but I know it can still be the MB/CPU. I just want to be sure I'm not leaving something out. Probably replacing the two would fix it but I don't know if its worth it. I don't really feel like putting any more money down on it. My uncle would pay me but I'd rather he paid me to just get his stuff off it so he can put in a more reliable computer.
    I replaced his old 250 Watt with a 350 watt.

    http://illusiongrouppcs.com/product...350-watt-micro-atx-replacement-power-supply-0

    I only paid $30 for it.

    Also I suspect perhaps it might be the button?

    I'd like to try and jump start it? But don't know how.

    Does anyone know how to start a PC with out using the switch?

    EDIT:
    Also note that I have no mouse or keyboard plugged in. NOt sure if this would disrupt anything.
    And before I replaced the OLD PSU it had a flashing green light at the back. Disconnecting everything but the MB from the PSU cause it to go solid green (not sure what it means). But no matter what it would never even turn on with the old one till I replaced it and now get the split second on/off.


    I'm just trying to provide as much info as I can right now.
     
    Last edited: Jun 14, 2011
  13. qubit

    qubit Overclocked quantum bit

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    @Aphex: Those power switches go to an ATX connector block on the mobo. Just trace the cable from the switch to the mobo. Alternatively, the mobo may have it marked as 'pwr sw' or similar.

    Pull the plug off the pins, which then allows you to connect them with a screwdriver momentarily. However, it won't be the power switch, I promise you.

    It'll power up just fine without the keyboard and mouse. The BIOS will likely complain without the keyboard, that's all.

    @95Viper: true, but it's unlikely, especially as his system behaves similarly with the new one.
     
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  14. 95Viper

    95Viper

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    Just me and my opinion; but, I would try a different PSU.

    I have not found hardly any good reviews of Athena PSUs. They look questionable. They say UL listed, I see no UL number on the stickers and UL site does not even return results on Athena.

    Goodluck, hope you get it solved...:)
     
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  15. AphexDreamer

    AphexDreamer

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    I suppose I can try a PSU from my other Desktop. It has a better one I believe.
     
  16. qubit

    qubit Overclocked quantum bit

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    You get a brownie point, 95Viper. :) I hadn't clicked the link and didn't see that Aphex is using a POS replacement PSU.

    Therefore, I'll second you that it could well be faulty and that he should try a quality PSU. My feeling is still that the mobo is faulty in the end, though.

    Again, check those caps for signs of bad ones. Any hint of it and you can bet that the mobo is bad. Replacing them can sometimes fix the problem if nothing else is broken, but it may not be worth the time, hassle and uncertainty.
     
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  17. AphexDreamer

    AphexDreamer

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    Guys problem Solved :D!!!

    Turns out it was the Bran New PSU!!!

    I tested the PC with a known quality PSU from another Desktop build of mine and it turned on!

    So back to Frys I go to buy another PSU and return the old.

    Thanks for all the help guys :)
     
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  18. 95Viper

    95Viper

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    Glad you solved it.;)
     
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  19. qubit

    qubit Overclocked quantum bit

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    Awesome! There's nothing as satisfying as a positive resolution. :toast:

    Yeah, those cheap PSU's are never worth it and could well kill your system. In fact, they're so shit, that if you get it free brand new, either eBay or throw it away.
     
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  20. AphexDreamer

    AphexDreamer

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    Frys closes at 9... so tomorrow.

    Also it would be nice if TPU had a Solved tag options for threads that get solved.
     
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  21. 95Viper

    95Viper

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    :toast: Nice idea.

    Ask a mod to add "SOLVED" to the title and close the thread.:)
     
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