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Computer Fails While Booting Up


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#1 why2kwill

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Posted 11 February 2008 - 03:32 PM

I have a HP 8485z Pavillion which is 10 yrs old. Recently I began having problems turning the machine on. When I press the power button it would begin to rev up and then shut down, tried a few times to no avail. I figured either the machine is finally dying or perhaps there is a loose connection. Took off the side panel and fooled around with the wires connected to the back of the on/off button and eventually I was successful in booting up but.. I'm not sure if I was successful because of what I did or is this merely the behavior of a machine that's ready to die. If it is just an electrical problem can someone tell me how to bypass the power switch? There are 6 wires connected to it. 2 behind the green light, 2 behind the yellow and 2 behind the power switch. The black wire connected to the green light came unattached thru me playing with it but I've managed to re-connect it using various household items. I'm planning on buying a new computer but can't afford to right now. In the meantime I really don't mind cutting some of these wires and splicing them so the on/off is not needed.
I'm just not sure which 2 wires to connect together. I would assume it's the 2 directly behind the power button. Thanks in advance.

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#2 Sneakycyber

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Posted 11 February 2008 - 05:07 PM

The 2 wires behind the green light are your power LED wires, the wires behind the yellow light are your HDD activity light (blinks when your accessing the hard drive) the wires directly behind the switch should be your power wires. You can follow these wires to the motherboard. When you have found out where they attach you can test the switch function using a voltmeter set to continuity test. You can also try triggering the computer to turn on by shorting the pins that the wires connect to. This should turn the computer on, some manufactures also have a reset switch on the front panel as well. Should your computer have a reset switch shorting these contacts won't power on the computer only reset it once its started. In a pinch you can purchase a momentary type push button switch from radio shack for a few dollars and install it somewhere in the case. I use part number 275-1547 for cmos reset switches for overclocking rigs. They should be perfect for what you need. Its cheaper than a new case.

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#3 why2kwill

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Posted 11 February 2008 - 06:10 PM

Thanks for your reponse Sneakycyber. If I understand you correctly I can snip the 2 power wires to the switch and reconnect them to the radio shack switch. I know a little about electricity and less about computer innards. I can see the motherboard but those pins are a little too cramped and tiny for me to fool around with. I'm not familar with momentary switches but from the picture I see it looks like it is spring loaded. Do I just hold it down til the computer powers up and then release it?

#4 Sneakycyber

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Posted 11 February 2008 - 06:41 PM

You should only need to press the switch it takes only a second to trigger the power supply to turn on.

Edit: Yes just disconnect the wires at the front panel switch and connect them to the new one. Did you try testing the original case switch?

Edited by Sneakycyber, 11 February 2008 - 06:43 PM.

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#5 why2kwill

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Posted 11 February 2008 - 06:58 PM

When I snip the power wires I'll test the switch, don't know how else to do it. If the switch is ok.. what does that indicate?

#6 Sneakycyber

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Posted 11 February 2008 - 07:10 PM

If the switch is ok, next test would be the power supply. Using this diagram unplug the main power connector to the motherboard (make sure the PS is unplugged first). Plug the power supply back in at the outlet and ground the green wire to any of the black wires. The power supply should turn on. Use a voltmeter and test each wire and make sure it matches the voltages listed on the site.

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#7 garmanma

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Posted 11 February 2008 - 08:59 PM

Deleted answer
Reread post, don't mind me

Edited by garmanma, 11 February 2008 - 09:11 PM.

Mark
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why won't my laptop work?

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#8 why2kwill

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Posted 12 February 2008 - 08:55 AM

I don't know where the power supply for motherboard is. Being inside the computer is all new to me so your instructions are a little over my head. don't have a voltmeter but one of my neighbors is an electrician so i could probably borrow his but then i would have to learn how to use it, which I probably could. When I test each wire I'll need a step by step because I don't know which wires to touch with the voltmeter leads. I'm assuming that the power supply will still be on when i perform this test and I also assume that the voltage measurements I'm looking for are the ones listed in the description section of the chart in the last link you sent me.
Lastly, can you tell me if the problem I mentioned with computer failing to boot is a typical symptom of a hard drive in it's death throes or strictly an electrical problem or both?
Thanks.

#9 garmanma

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Posted 12 February 2008 - 09:09 AM

The machine should turn on, bad hard drive or not. The easiest way to see if it is indeed the power switch button is to remove the 2 wires from the switch on the motherboard and using a screwdriver, touch the 2 pins together that the switch wires were plugged into
Mark
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#10 garmanma

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Posted 12 February 2008 - 12:42 PM

Here's a tutorial on how to build a computer with good pictures. It should help you out
http://www.buildeasypc.com
Mark
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why won't my laptop work?

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#11 why2kwill

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Posted 12 February 2008 - 05:00 PM

Thanks garmanma, I'm working my courage up to tackle it.

#12 why2kwill

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Posted 14 February 2008 - 11:51 AM

computer froze so i had to use the power switch to shut it down. When i tried to boot up and jiggled the wires going to the power switch the machine came on then went off and came on again without me touching anything. I disconnected the ps plug to the back of the computer, cut the wires going to the on/off switch. then spliced the wires together and...nothing.
I pulled the pin with the power and led wires leading to the motherboard and shorted the power pins tohether and it booted up.
If the machine freezes up again, I assume I'd have to pull the ps plug again, to shut it down. I also assume that the problem now appears to be either in the pin or the power wires leading from the pin to the on/off switch..correct?

Edited by why2kwill, 14 February 2008 - 12:11 PM.


#13 garmanma

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Posted 14 February 2008 - 12:52 PM

You should be able to shut down by going to Start>Turn Off Computer, and select Turn Off
If it tries to shut down but keeps rebooting, then you have a different problem
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#14 why2kwill

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Posted 14 February 2008 - 01:10 PM

am I correct in thinking that the problem is either the pin or the 2 power wires leading to the on/off switch?.. and if so, buying one of those momentary switches wouldn't help until the pin/wire problem is resolved?

#15 Sneakycyber

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Posted 14 February 2008 - 05:37 PM

When you "spliced the wires together" did you leave them together or just touch them? The wires are not meant to be connected, only make contact then left apart. This sends a signal to the motherboard to trigger the power supply to turn on. If you leave them connected the computer thinks your trying to reboot, or turn the computer off, depending on the motherboard power options. Mine for example if you press the button once when its off it powers on, if you press it when its on it powers down through windows, if you HOLD it in it forces a shut down.

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