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[SOLVED] PC won't boot after disconnecting power

1296 Views 3 Replies 2 Participants Last post by  Tyree
First, I really appreciate this forum being here; I hope it turns out more fruitful than Gigabyte tech support. I'll try to provide as much information as I can.

I am reassembling an old computer for a friend. Specs are as follows:
Gigabyte GA-MA790FXT-UD5P (Dual BIOS, if that makes a difference)
4GB Crucial RAM
AMD Phenom II x3
40GB Western Digital HDD (soon to be upgraded)
NVidia 9800GTX+ Black Edition
500W PSU
Wireless Adapter
Windows 7

The PSU and Wireless Adapter are new. I tested the PSU and it works perfectly. I also have switched with another PSU that I know works because I use it every day to verify that the problem is not the PSU. The HDD is really old; it works but I intend on replacing it. All of the other parts were purchased circa March 2009. Also, the first thing I did with the rebuild was check and replace the CMOS battery.

The problem I was having was that the computer would not boot without being jumped by connecting the green and black cables on the 24-pin connector with a paper clip. With the help of Gigabyte support, I was able to load the fail-safe default settings and optimized settings for BIOS. That allowed me to reboot the computer without using the paper clip.

But that didn't solve everything. If I disconnect the computer or flip the switch on the back of the power supply (then reconnect everything, of course), the computer will not boot or respond at all. No lights come on. No fans. Nothing. It's as if it isn't receiving power.

After a month of back-and-forth with Gigabyte Tech Support, they suggested I update the BIOS from F3 to F7 or F8N. I used @BIOS to perform the update and now have F7 on the computer. That didn't help at all. The update ended in an unresponsive black screen. There was a white underscore at the top-left, as if promting a command, and a green square with an "N" next to it near the center. After 2 hours of nothing, I shut the computer off and booted it back up. The update applied itself and Windows7 loaded. I turned it off, flipped the switch on the back, waited 10 seconds, and attempted to reboot without the jumper. I got nothing.

I've been at this for over a month. Gigabyte has given up on it, saying I should RMA it but it's after warranty. I have scoured the internet for information to no avail. Please help.:cry:
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Re: PC won't boot after disconnecting power

Specs and configuration (how many sticks and what size) on the RAM?
Brand & Model of the PSU?
Remove the Hdd and see if it will power on and boot to the Bios?
Test on the bench precisely as listed below.

Remove EVERYTHING from the case.
Set the motherboard on a non conductive surface. The motherboard box is perfect for this. DO NOT PLACE THE MOTHERBOARD ON THE STATIC BAG! It can actually conduct electricity!
Install the CPU and heat sink.
Install 1 stick of RAM.
Install the video card and attach the power supply connection(s) to the card if your card needs it.
Connect the monitor to the video card.
Connect the power supply to the motherboard with both the 24pin main ATX Power connection and the separate 4 pin (Dual Core CPU) or 8 pin (Quad Core CPU) power connection.
Connect power to the power supply.
Do NOT connect ANYTHING else. Make sure you have the power connector on the CPU fan connected.
Use a small screwdriver to momentarily short the power switch connector on the motherboard. Consult your motherboard manual to find which two pins connect to your case's power switch. Then touch both pins with a screwdriver to complete the circuit and boot the system.

If all is well, it should power up and you should get a display. Then assemble the parts into the case and try again. If the system now fails to boot, you have a short in the case and need to recheck your motherboard standoffs.

If the system does not boot after this process, then you most likely have a faulty component. You'll need to swap parts, start with the power supply, until you determine what is defective.
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Re: PC won't boot after disconnecting power

You're welcome and glad you found the problem.
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