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Power-up pins

Discussion in 'Hardware' started by playtom, Mar 1, 2009.

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  1. playtom

    playtom Thread Starter

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    How do you identify the power-up pins on the motherboard and what to do to short it? I have extracted some advice from the internet from someone who had the same computer problem as me and he fixed it with this method. Just wanted to ask some of the experts here how to do that since i'm not an electrician and are pretty much oblivious when it comes to these kind of tasks.

    Here's the original paragraph from him which i didn't understand much of:

    "Try this once..take the CPU out from the motherboard...then short the power-up pins on the motherboard(that is...the pins to which your power-on switch of CPU is connected) with the help of screwdriver.

    I learned this just yesterday....my pc was giving trouble and then it stopped booting..nothing on the display...fans running.I took it to the vendor...and he did this procedure...and the pc started booting again.Told that the BIOS hangs due to which this problem happens.

    So you can also try this and see i if it works for you....best of luck."
     
  2. Triple6

    Triple6 Moderator

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    These are the two pins that the front ATX power switch connects too. You refer to the motherboard manually or the labels on the pins or switch connected tot the pins to find them. This is pretty much useful for diagnosing one problem, a faulty front ATX power switch - it simply takes it out of the equation and rules it out as being broken. So in a working system you follow the wires from the front panel switch to the motherboard, unplug the stick and use a screw driver or pen or anything conductive to 'short', connect the two pins together for a second to complete the circuit and power on the system.
     
  3. playtom

    playtom Thread Starter

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    I did some research on the internet about front panel switches after reading your reply. Most of the pictures regarding the front panel switch had different number of pins on it, mine had 9 when i unplugged the connector from the front panel to the motherboard. My PC's motherboard specs are here if anyone wishes to elaborate further: http://h10025.www1.hp.com/ewfrf/wc/...08&lc=en&dlc=no&cc=no&product=3190729&lang=no

    So, since there are more than 2 pins when i unplug the connector(9 in total), how would i proceed to short them and which one would i use?
     
  4. Triple6

    Triple6 Moderator

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    Yes, a lot of big brand name system use a single plug. In that case it can be trickier to locate the right pins, try to follow the wires back to the front panel switch to see which two are for the power switch.

    And its unlikely you are missing a tenth pin, most board do not have all then 10 pins, and sometimes much less, thats simply up tot he maker of the board.
     
  5. playtom

    playtom Thread Starter

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    Right now my PC is broken and when i press the power on button the fans (system, power supply as well as the cpu fan) would start to spin but once it reaches the full RPM, which takes a fraction of a second, they all recede down to a halt.

    I found the power up switch pins, which trace back to a black and yellow wire bunched together in a bundle. The weird thing is that when i unplug the connector while the my PC is plugged into a power outlet, a screwdriver connecting two adjacent pins out of the 9 would give me the same symptom, the computer fans would start up and then die down quickly.

    Here's the really weird thing: when i push the screwdriver deeper into the space between the two pins, the fan would start up for about 3 seconds and then die down. This is normally what my computer would do on start-up when everything is fine. This only works with the screwdriver and not the single connector plug so that means my computer is still broken unless the plug will simulate this.

    I'm starting to think that the plug is faulty or that the pins needs to be replaced somehow.
     
  6. Triple6

    Triple6 Moderator

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    Unlikely its the plug, all the switch does it complete a circuit for a split second to start the computer then it no longer plays any part unless pressed or shorted again. Your problem is elsewhere. I'd be thinking a faulty power supply next, swap in a known good power supply and see if the computer turns on and stays on.
     
  7. playtom

    playtom Thread Starter

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    If i only had another ATX power supply, then i'd be happy to swap them. The PC i'm typing this message on is a 9-year old dell GX110 which is vastly different from this 2 1/2 year old system that i'm trying to fix.

    I did check the PSU by opening it up and inspecting the capacitors. All of them seems to be in good condition, not leaked or vented. There is no burn marks or smell coming out of it so i'd say that its in good condition. Prior to this i messed around with the CPU socket and somehow made the fans to spin forever when i power up the computer. It would make no sense to me if the power supply is failing and can supply un-interrupted power to all the fans that way.

    So here's something of mine that i have to ask the experts here for approval before trying: sticking a paper clip between the two pins at the point where it triggers the 3-second spinning action that my fans would normally do, hopefully not needing to use glue or adhesive but allowing that paper clip to substitute as the plug. I'd be happy to leave my screwdriver down there but since it's pretty big and loose it wouldn't stay on there and power on my computer as it would if weren't broken.
     
  8. Triple6

    Triple6 Moderator

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    A visual inspection yields very little. Power supplies partially fail all the time, where they can supply some voltages and not others or supply incorrect voltages; fans are not picky about correct voltages, electronic components are.

    BUT now that you've said you had been messing around with the CPU heatsink and fan then that may be the problem. If the heatsink is not correctly seated or the fan is not plugged into the correct CPU fan header then the system will shut down. It only takes a few seconds for a modern processor to overheat and cause the system to power off to protect itself or have the system power off if it cannot read the CPU fan correctly.

    The ATX power switch is a Momentary switch, it should not be permanently shorted and the system will not work with it permanent shorted. It is not like a light switch which has an on and off, it only completes the circuit for a second to initiate the system to begin powering on then it returns to an open position.
     
  9. playtom

    playtom Thread Starter

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    I'll try to reseat everything on my computer, including the heat sink as well as the RAM module. Locating all the power supply wires to the motherboard components will be the first on my list, hopefully reseating them might work. The front panel connector is probably fine as you've said so i'll leave that alone.

    Either that works or i'm getting a new computer. Been wasting way too much time on fixing this thing. That time spent could easily be saved for a few hundred bucks which will get me a brand new system with better specs.

    Thanks for all your help. I'll soon start shopping for a new system in case this one won't work after all that.
     
  10. Rich-M

    Rich-M

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    I have to agree with Triple as usual. The power pins and power switch are simply an on/off mechanism and this sounds like a bad psu. Branded mfgrs use exactly the needs of the system in a psu so there is no leeway for change or failure. It could also be heat and an hsf failure. Why not expose the board and watch system inside to see if the fan on the cpu is turning at all or stays on as it could be a bad hsf or worse the motherboard connection.
     
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