Solved After mains if off the computer wont start

May 18, 2011 at 00:04:56
Specs: Windows Vista, Intel quad core 4Gb
This is the strangest problem I've seen in 15 odd years of computers. It's a Gigabyte ga-ep31-ds3l with an Intel quad core (sorry forget what speed) Nvidia GeForce 8800 PCI-E 4 GB ram and 680W power supply, one sata drive 500Mb and sata dvd-r. My friend brought it to me, it wouldn't turn on. About 6 months ago I had replaced the power supply, I thought that would be the problem and maybe he need a surge supressor (lives out of town a bit). I know I should have tested the supply first, but I bought one installed it, same problem..Damm... I then got a second hand MB same type, guess what same problem...Double Damm... So I jumpered the green wire to ground (force power supply on) the P/S turned on (Pok grey wire was at 5 V) and computer booted. And a single press of the front button and it turned off, another press and back on. So I unpluged the mains and took it over to where my screen, KB and mouse are. Guess what it won't turn on again..I was getting frustrated and pressed the power on button 10 or a dozen times. Lo and behold it turned on and booted up! So I now have this condition, if I force it on or press the button nunerous times it will come on, and then works fine, one press off (or shutdown if Vista is up), one press on. Until you turn off the mains, then it it wont start. So I figure it can only be the on/off switch, my multimeter tells me it is ok, Hmmmm, so I swap it with the reboot button, still the same, I get another push button switch, wire plug etc and fit a temporary new power on button. It's still wont turn on!!! without lots of pressing (and swearing). I have tried it with no video card, no hard drive or DVD connected, no USB stuff connected, no KB or mouse, I have done a set defaults in bios, nothing changes the problem. Tonight I'll try a clear bios and advise what happens (if it works you'll hear the cheering and I live in Australia). So both motherboards and both power supplies and both on/off switches do it. If I fudge it so it turns on every thing works fine right up to where I disconnect mains power. (yes I shutdown and it turns off before I pull the mains plug). I did try disconnecting the on switch and shorted the pins on MB with a pair of pliers (yeah rough I know but I am at my witts end) the damm thing powered on like a bought one!!!....Maybe it just wants to live here. ANY ideas will be greatly appreciated.

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May 18, 2011 at 01:37:41
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I don't believe it, I cannot believe it, I won't believe it, I fixed it!! All thanks to this forum. I know no replies yet, but as I was writting it out a little spark went off in my grey matter. Nothing on the USB?? It didn't click until I got back to the computer to do the clear cmos, what is the memory card reader in the front connected to? Damm it is connected to the front USB header. I disconnected it, and immediatly the computer will now turn on every time with just one push of the button reguardless of how long it has been off from the mains. A lesson for everybody, you can get so focused on a problem that you don't see the obvious. So beginners (newibies) when some one suggest "have you checked the cables, have you reseated the cards, have you disconnected ...whatever", they are not being condescending, they have probably learned the hard way just as I do, If you cannot find the problem you not looking in the right place.....One the other hand (as an electronic tech) I would love to know the reason why, if it was shorting a voltage then why work when forced on? Guess I'll never know. It has occured to me that when shutdown a computer still puts power to the USB, if you have a laser USB mouse or battery charger you'll see that. Thanks, and maybe this post will help someone somewhere some day....At least it helped me..LOL

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