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Laptop turns ON then Turns OFF

Discussion in 'PC hardware help' started by ken_919, Nov 1, 2010.

  1. ken_919

    ken_919 Regular member

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    I have a friend's laptop which is a Compaq Presario F700 laptop that turns off the moment I turn it on. I push the power button, Power light, hard drive light, and trackpad light come on. Two seconds later, the laptop shuts down. I have tried powering it on using just the AC adpater with no battery, just the battery, both, tried another good ac adapter but still same result. When I have the battery in and the ac adapter plugged in, the charging light is lit up blue. I have reset the hard drive, memory, cd drive, and also tried using just one stick of memory but still same exact result. I have also tried doing a Hard Reset that I read on HP's forum - pull the battery and the AC plug,push the power button and hold it for about 30 seconds release. put the battery back in and plug in the AC. push the power button and it should turn on. I have cleaned all the fans so everything looks good. I did some searching online about this model and sounds like quite a few people are having this exact issue or issues very similar. My friend said the laptop went to a blank screen but still sounded like it was running and left it. When I try to power it on, I don't get display but not sure if I would see anything within the 2 seconds it "powers on". It does kinda sound like the fan(s) attempt to spin but again, hard to tell when it powers on for about 2 seconds. Any suggestions to try?
     
    Last edited: Nov 1, 2010
  2. KillerBug

    KillerBug Active member

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    Quite often, a laptop can be fixed with a simple rebuild if you have the time...I honestly don't know why this is anymore; I have fixed dozens of laptops without finding any issues during the tear-down, and without replacing any parts. Sometimes this is the only way to remove the CMOS battery, so it almost makes sense for those systems...but other systems have CMOS batteries that can be removed without removing the mainboard, and they respond to rebuilds the same.
     
  3. ken_919

    ken_919 Regular member

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    Just to clarify, the laptop doesn't keep restarting itself. It bascially won't power on. When I attempt to power it on to use it, it powers on for a second or two and then shuts down.
     
  4. dlasko

    dlasko Member

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    Ken_919. I too have the same problem. What was your outcome? I have the laptop taken apart down to the motherboard (my first time taking apart a laptop). New power switch, new power connector board, new power adapter. Waste of money. The exact same thing happens when I push the power switch after replacing parts. I click the power switch and then all lights show up on mobo, and then turn off within a sec. After hundreds of searches, I actually think even the pros give up, because I have yet to find one answer to this problem. I really do not think it is the mobo and if it is, I would love for someone to tell me how I could test it before getting a new laptop, which I can't afford.
     
  5. dlasko

    dlasko Member

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    KillerBug: Are you saying that a bad CMOS battery will keep the F700 with power up problems that ken_919 and I have from starting up?
     
  6. ddp

    ddp Moderator Staff Member

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    he is not saying the battery is bad but to reset the bios back to factory defaults is to remove the cmos battery pack for 20 count then reinsert battery. laptops do not come with cmos jumpers so removing cmos battery is the only option. have done similar on stubborn desktop motherboards by using the cmos jumper.
     
  7. dlasko

    dlasko Member

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    Thanks ddp. I have the laptop tore apart to the mobo and yes, I took out the CMOS battery and put it back in already. If the CMOS battery is completely dead and never showed signs of dying, can a dead CMOS battery still be the culprit? I don't think so, because I am bench testing and don't need to boot into anything. I just want the power to stay on. Any other ideas on what could be the problem? The board looks perfect with a new (not needed) power connection board and new (not needed) power switch. Want to buy some working parts? Still the same thing, power on, all lights good, fan starts, power off within 1 sec and yes I have one ram in (tried in both slots). I need to state that the computer had absolutely no problems other than the battery (not CMOS) would not hold a charge and a new one was purchased from HP.
     
  8. ddp

    ddp Moderator Staff Member

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    top of the can capacitors flat not domed? cmos battery is not causing the problem. do you have or can get some heatsink compound\paste as maybe cpu heatsink needs to be reseated which is were the paste comes in?
     
  9. dlasko

    dlasko Member

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    Please stay with me for a few. What do you mean "top of the can"? All the capacitors are flatish. Heatsink looks and feels so tight, so right.
     
  10. ddp

    ddp Moderator Staff Member

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    the can capacitors have to be flat top not domed. cpu heatsink compound might be dried out causing cpu to overheat & shutdown. is cpu fan spinning at all?
     
  11. dlasko

    dlasko Member

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    Scratch my last stupid post. The can capacitors are completely flat. The laptop was not used much and so I don't know why the compound would dry out. The cpu fan spins for a sec just like the leds come on for a sec.
     
  12. ddp

    ddp Moderator Staff Member

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    other option is that part of the onboard voltage converter is not working or not working
    properly thereby causing system to shut down just like a regular psu in a desktop case.
     
  13. dlasko

    dlasko Member

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    What does it look like when compound has dried out on a heat sink? How do you test to see if the onboard voltage converter is bad?
     
  14. ddp

    ddp Moderator Staff Member

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    the converter is part of the cpu motherboard & is near the power connector. it uses different components to convert 19volts to 3.3 & 5volts.
     
  15. dlasko

    dlasko Member

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    I left off one important item. All the led's come on for a sec than off but the blue light where the power adapter plugs into the power connection board stays on. Still a possible converter problem?
     
  16. ddp

    ddp Moderator Staff Member

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    i think still converter issue & not talking about external power adapter.
     

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