My Computer Won't Start (DEAD)

[Reloadron]

Overall Troubleshooting a computer that does nothing when the power button is pressed.

This guide is written to help the home computer enthusiast whose computer will not start when the front panel power button is pressed. The guide assumes nothing at all happens and the system does not start, the fans don't spin up, there is no post or BIOS activity and nothing at all happens. This guide assumes the enthusiast has no specialized tools such as a DMM (Digital Multi Meter) to troubleshoot the system.

First with the system unplugged from the AC mains power and the rear PSU switch (if applicable) in the OFF position remove the case side panel as applicable to view the inside of the system. Once the side panel is safely removed connect the system to mains AC power and turn the rear PSU power switch to the ON position. Additionally make sure all connectors to and from the motherboard are tight and secure, these include the 20 or 24 pin main power connector and auxiliary CPU power connectors.

NOTE: Make sure the AC mains power is an active working power source. If using any form of switched power strip make sure it is on. Make sure no household circuit breakers are tripped or fuses blown.

With power ON visually inspect the interior motherboard surface for a glowing LED. Most of today's newer motherboards include a power LED which should be ON anytime power is connected to the system and the rear PSU power switch is on. We suggest you check your motherboard manufacturer's manual for the presence of this LED as it can be a very important and useful troubleshooting aid.

The above image is taken from an Asus motherboard manual. The LED should glow brightly anytime power is applied at the rear of the unit and the rear PSU power switch is in the ON position. This LED when illuminated indicates the presence of 5 Volt SB (Stand By) power to the motherboard. This 5 Volt SB power is essential for the power supply to perform a normal start when the front panel power button is pressed. Should your motherboard have one of these useful tools and the LED is not illuminated with the afore mentioned conditions met of known good power applied and the rear PSU switch in the ON position there is a strong possibility your PSU has failed and should be replaced with a known good PSU capable of the necessary power to run your system.

The next logical steps will be some fault isolation. Assuming the 5 Volt SB led is glowing check the motherboard connection where the case connects with the motherboard. This is generally a pin header as can be seen in the below image.

NOTE: Consult your motherboard manual for the location and pin out of these pins. Different manufacturers place the header in different locations as well as use slightly different identification convections. Common terms are PWR-ON, ATX-SW (as above) and others. Consult the manual and don't try to guess. If your manual is lost they can frequently be downloaded from the manufacturer's website.

Remove the front panel leads connected to the illustrated pins for Power On and jumper (short) the pins together. The case front panel power button is a momentary normally open switch, when we press the button it shorts the pins it is connected to. This step eliminates the possibility of a faulty power button or wires from the power button to the motherboard. Does the system start when the pins are shorted? If when the pins are shorted the system starts the problem is likely a front panel power button or the wires from the power button are damaged. Remove and replace the power button and associated wires. Most case manufacturers will replace these parts free of charge. Contact your case manufacturer. Should shorting the pins produce no results, replace the removed wires and let's continue.

The following steps require a little manual dexterity depending on placement of the motherboard main power connector. When the pins we mentioned are shorted by a momentary closure of the front panel power button the motherboard uses the always present 5 Volt SB power we mentioned to send a signal to the PSU through the main PSU / Motherboard connector. This is accomplished through pin 14 of the older 20 pin connectors and pin 16 of the newer 24 pin connectors. This pin is commonly known as the PS_ON pin and is a Green wire. It should be the only Green wire in the connector. We are going to jumper (short) this Green wire to any Black wire on the connector.



This is done with the PSU connected to the Motherboard. Carefully slip the jumper (wire or a paper clip bent to shape) down beside each of the Green and Black wires. The jumper must be inserted deep enough to make contact with the metal pin sockets in the connector. This test simulates a Logic Low being applied to the PSU on the PS_ON line and is what the motherboard logic circuits would be doing. This is a momentary test! Does the PSU power up? Do the system fans begin to spin? Remember this is a momentary jumper affair, do not leave the jumper in for any length of time. If the system came to life the problem is likely a faulty motherboard, something is precluding a power start command from reaching the PSU.

Another test and a final step we can try is disconnecting the motherboard main power connector and if present the 4 or 8 pin CPU power connector. Leave the optical drive power connected as well as the hard drive connector. Again, with no power connected to the motherboard apply the short between the Green and any Black wire in the connector. Does the PSU start? Do the optical drives show activity? Does the PSU fan start? Again if the answer is a resounding YES the likely problem is the motherboard. However, if again there is no activity then the likely problem is a failed PSU.

These are the first logical steps in troubleshooting a system that simply does nothing when the front panel power button is pressed. Though not foolproof they should afford the home computer enthusiast a basic idea of fault isolation.

Written as a troubleshooting aid for the members of the HL (HardwareLogic) forums:

http://forums.hardwarelogic.com/

Sunday 06 January 2008

Ron

[stinger608]

Great troubleshooting guide RON!!!!!

[Yellowhello]

Excellent! I hope this makes the frontpage!

[Reloadron]

Thanks alot, much appreciated. If anyone can think of other things or subjects let me know. I am looking for what to add to fan speed before I move it here.

Thanks Again
Ron

[StevieRay]

Hey this is great advice. I am a novice, but want to add/ask:

I had this issue and posted in troubleshooting and received this same advice you gave. Wish I saw this earlier. But, as a novice, I read a bit about symptoms of a PSU failure. I also read that that if the LED is on, then the mobo should be fine. Being a little mechanical in nature and becomeing more technical, I purchased an $8 PSU tester (by Antec). Pulled out the PSU which is a very simple thing to do IMO. Tested it and bammmo, failed PSU. Then with some great HL advice purchased and installed the new PSU. Back up and running in less than an afternoon.

Should that go along with your recommendation? I only ask because the steps you give I assume could be shortened if you identify the faulty PSU earlier. Or should you always perform said steps in order to make certain?

Thanks for hearing me out if you do...StevieRay

[Reloadron]

Originally Posted by StevieRay

Hey this is great advice. I am a novice, but want to add/ask:

I had this issue and posted in troubleshooting and received this same advice you gave. Wish I saw this earlier. But, as a novice, I read a bit about symptoms of a PSU failure. I also read that that if the LED is on, then the mobo should be fine. Being a little mechanical in nature and becomeing more technical, I purchased an $8 PSU tester (by Antec). Pulled out the PSU which is a very simple thing to do IMO. Tested it and bammmo, failed PSU. Then with some great HL advice purchased and installed the new PSU. Back up and running in less than an afternoon.

Should that go along with your recommendation? I only ask because the steps you give I assume could be shortened if you identify the faulty PSU earlier. Or should you always perform said steps in order to make certain?

Thanks for hearing me out if you do...StevieRay

We hear everyone out, that is why we are here.

Troubleshooting a PSU problem can be a painstaking task. The fact that a little LED glows bright on a motherboard merely indicates the presence of the 5 Volt Stand By power I mentioned in the article. That does not in any way indicate a good PSU. That 5 volts is derived from a seperate and independent transformer in the PSU and says little as to if the rest of the unit is working.

Those little PSU testers, though helpful as in your case are OK. However they really do not tell a user if the PSU will function under a load. Again, considering cost, they are a useful device.

Glad you enjoyed the little article and even more pleased you enjoy the forum.

Thanks
Ron

[gvblake22]

Great stuff! You should also add a bit about the general process of using the ever-popular CLR CMOS jumper and battery.

[Reloadron]

Originally Posted by gvblake22

Great stuff! You should also add a bit about the general process of using the ever-popular CLR CMOS jumper and battery.

Damn hindsight! Quite true as another simple step that solves many a problem.

Ron