CPU won’t start but Motherboard has green led light

Asked By juliet 510 points N/A Posted on - 05/13/2011

Before I left for a trip I turned off my 350 Antec power supply. And when I came back, I hit the power button and there it goes "my computer is dead".

• I took off the side panel to see if my motherboard was getting power, fans are not working and no sounds so I reconnected it and nothing happened except for the green light on the Motherboard.
• I tried wiggling the cord around and unplug it and plug it back in and it still won't turn on.
• I heard some spark or static discharge something when I unplug it and re-plug it again, I smelled the unit around the fan area and it smells like burned. So I bought a new Power Supply and pray that it would solve the issue, then I installed it properly but "GOD why it is not working"? I've already tried swapping power cords, but still it doesn't work. I'm tired of this problem.

Is there any hopes left for my PC? Can this still be fix?

Is this because of the bad power from the wall or the power supply itself? Somebody help me on this please. I badly need your advice!

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Best Answer by Gerard Baylor

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Answered By Gerard Baylor 0 points N/A #92753

CPU won’t start but Motherboard has green led light

Hi Juliet,

Tough luck for having a dead PC it seems. But the way you described it gave me the impression that you have the guts to open up your PC and tinker around. For starters, the Antec 350 was designed for use with a 20 or 24-pin ATX version 2.01. It complies with the latest Serial ATA devices and support legacy floppy drives as well. Its main features include an over current protector for surges, and a short circuit protector.

 

Now despite the features outlined above, it doesn’t mean that your power supply is invulnerable. It still is, despite the numerous protection circuits the module employs. Let’s go in-depth to see what went wrong.

 

1. AC line voltages can be as fickle as a girlfriend and as volatile as a mom. Transient and fluctuating voltages can fry power supply circuit boards just like that. Most power supply modules place a voltage dependent resistor (VDR) that automatically blows before power runs through the rest of the circuit, particularly the primary side. Isolating the cause of your problem is the first step.

 

Get or purchase a digital multi meter from any electronic store. Then check here for  pin configuration guide for your ATX power supply:

 

ATX Power SUpply Connector Pin Assignment

 

Power up the computer and measure the DC voltages from the main power connector, peripheral power connector, +12V power connector, and serial ATA connector using the pin configuration guide as reference. Compare the voltages with the ones listed. They should be of the same value.

 

If the DC voltages conform to what is listed on the pin configuration guide, then we have to come to the conclusion that your motherboard was affected by the power surge that hit your original power supply. That’s why replacing the power supply did not solve your problem. If you get no readings at all, unplug all power connectors from your power supply to the motherboard. There may be a short circuit on the motherboard, which in turn activates the short circuit protection in the power supply module.

 

2. Now the next part is determining what other components were affected by the fried power supply. Although we concluded that the motherboard could be defective on the first part, let’s not solidify our stand on it yet. Isolate the rest of the peripherals one by one by disconnecting each one, part by part, powering up to test after removal and proceeding to remove the next one till all have been removed.

 

Start off with the peripherals connected (hard drive, floppy, keyboard and mouse). Did it power up properly with one of them disconnected? If it did, take note of the faulty component and replace. If it did not move on to the next part of the troubleshoot.

 

Next is the memory module. Remove all the modules, borrow a known good working memory module from another PC and insert that into your motherboard slot. Power up to check if running. Another trick is to test the ones you removed from your motherboard and place it on another working set to see if it gets detected. Note your conclusions. If memory checks out fine set it aside. Do the same for the CPU, Graphics card, and sound card/network LAN card. Replace and substitute if necessary. Note your progress.

 

Now make your conclusions. Based on the procedure you just did, you most likely have found out by now which is faulty. Majority of the faults rest upon the motherboard, the memory modules and hard drive come in a close second, and the others a poor third. Salvage the parts you have tested as working and purchase replacements for the ones you found defective. Reassemble your PC and test.

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• Posted on - 05/14/2011
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Answered By ijames 0 points N/A #92754

CPU won’t start but Motherboard has green led light

Hi Juliet,

I am really sorry for your computer. I would like to tell you what may had happen what can be done for that. First of all if the light of motherboard is on then it does not mean that your power supply is alright. Motherboard have so many components that may be damaged easily so may be while opening your PC unknowingly you may have broke any component so the new power supply is not working.

 

The next thing can be that the new power supply that you have bought may be faulty so if you have any friend who lives nearby your house can help you, you may borrow the power supply from him and can check it again. But firstly once again check properly that whether you have plugged all the connections or not. If all that will not work then it will be better to take your motherboard to service center for checkup. Wish you a luck and please be very alert while opening your PC cabinet.

 

Thanks,

 

James

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• Posted on - 07/19/2011
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