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So, my laptop is a Dell model # pp39l. The little red wire connecting the power button to the battery is severed. Past warranty, tech support tells me it's a few weeks and a few hundred dollars (yuck) for what seems like a benign problem. I am more of a software than hardware guy; nonetheless, being quite fond of my programming companion, of a frugal disposition, and curious, I'd like to fix it myself.

My naive first impression is that the power button is an "ignition" that sends a spark somewhere (battery, monitor, mainframe), which then triggers boot. Obviously, because of functionality like "sleep", it also sends other signals. Despite my dissection and attempts, though, I don't know if it's possible to simply jumpstart my computer by sending a current (what amperage, I know not) through the severed wire. If not, then is there some more sophisticated hack I can do?

Thank you

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What you call a "power button" on a PC or laptop is a low-voltage logic input to the power logic circuit. If the red wire is "severed" then you have a broken wire, not a broken switch. –  sawdust Jul 29 '11 at 0:26

2 Answers 2

Where is it severed? If you have space on both sides just cut the shielding and wrap it in electrical tape.

If not...how do you feel about learning to solder? ;-)

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Typically it is opposite of what you are theorizing. On a typical motherboard (laptop or desktop) there is a header pin (or wire in your case) that when the button is pressed it actually makes that wire touch ground (the negative side of the battery/power source)... This implies that there is a little bit of charge already tied to that wire and when it is 'shorted out' so-to-speak it signals the computer to turn on.

If this wire is simply broken, why not solder it back together? ... and most of the time this power button does not connect directly to the battery, are we sure we are talking about the same button, or same wire??

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This is the case on all ATX compliant designs. There is a POWER+ header on the motherboard providing 3.3v (iirc, possibly 5v) at negligible current and a POWER- header. When POWER- lights up the motherboard bootstraps. Power/sleep/etc logic is handled by software on the motherboard, the switch is just a dumb logic input. On laptops, the wiring to the power button is probably soldered straight to the motherboard somewhere. All you need to do is hook that wire up. –  jcrawfordor Jul 29 '11 at 4:06
    
Or, you could ghetto it and just boot the machine by shorting the wires together. Computer techs often boot machines they're working on by tapping a screw driver to the power switch headers. –  jcrawfordor Jul 29 '11 at 4:08

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