possible dead MOBO

[asusfrustration]

My computer will not power up. I have checked the power supply with a block tester and there is no problem there or with the switch. I have an ASUS A8N SLI premium board and the green led lights up when power is supplied to the board but absolutely nothing happens when the power switch for the computer is pushed. I have removed all peripherals, held in the switch for 10 seconds and still no luck. Any suggestions?

[dcc]

Have you metered out the momentary switch? If you don't have a meter disconnect the switch from the header and short the two terminals and see if it fires up. Remember that it's a momentary switch action, so just make a quick contact between the two terminals.

[asusfrustration]

Thanks for your reply. If by momentary switch you mean the off/on switch, that is what I used to send power to the block tester. Since this worked I assume the switch is in good working order.

[dcc]

A momentary switch is differentiated from a on/off switch in that a on/off switch when placed in the on position will stay there until you turn it to the off position. A momentary switch only stays closed/on as long as you push the button. The power button on your case is a momentary switch.

You wrote that the LED lites up on the motherboard when it's powered, but that nothing else happens. Does this mean the CPU fan doesn't spin? If this is the case you may have a problem with the motherboard.

[asusfrustration]

That is what I am saying, the CUP fan doesn't spin or anything else. When I checked the switch and power supply with a block tester, the cpu fan etc. came on. That is why I believe it is the motherboard. Is there anything I can do to the motherboard to diagnose where the problem is or any jumpers I can move that would make any difference and restart the board?

[PCsrivastava]

Check Ur Mother board With One of your frinds Power Supply (means SMPS) Try It

[dcc]

Two things to look for on the motherboard would be bad caps and burnt traces which would be signs of a short.

[JANINE]

Dcc is right in what he says but however I would at this stage suggest swapping out the PSU for one that is known to be fully functioning as its possible that one of the rails on your current PSU might have blown.

If you have the right tools and feel confident in testing electrical components of your PC you can try testing each rail individually. Please feel free to view this web article i found.

http://forums.extremeoverclocking.com/showthread.php?t=137886

[dcc]

Is your PSU a 20 or a 24 + 4 connector type? If it is the 24 + 4 is the small square four pin connector connected to the motherboard?

[asusfrustration]

I have a 24 pin connector and all was connected properly. My PSU checks out fine. There are no burnt caps or charred areas on the board. There was no smoke etc. it just suddenly would not start! Any other suggestions?

[dcc]

Is your PSU a 20 or a 24 + 4 connector type? If it is the 24 + 4 is the small square four pin connector connected to the motherboard?

When you look for bad capacitors you're not looking for burns, a bad electrolytic capacitor will look bloated, like a can of warm pop that has been shaken up, the top of the capacitors should be flat not domed. It may also have a liquid discharge at its base.

The reason that I'm asking specifically about the P4 connector is because CPU is powered up from it and the motherboard may not power up without it, and btw...your block tester doesn't test the output to that connector. It may tell you what is happening at the different rails but not what is going on with the wires or connectors.

[asusfrustration]

Yes, the square 4 pin connector is connected to the MOBO. Remember, all was working fine, I did not change a thing and it just quit working. I believe the PSU is OK. The only other possibilities are the MOBO or the CPU and I don't know how to figure out which is bad except to get a new MOBO. I would like to be able to make sure I don't buy a piece of equipment that wasn't broken. The MOBO looks the same as the day I installed it. I cannot find any areas that appear bad, swollen capacitors etc. I appreciate all the ideas you are throwing at me.

[dcc]

Remember, all was working fine, I did not change a thing and it just quit working.

Actually...this is the first time that you have mentioned that you had it working.:eek: I thought you were trying to get this to fire up for the first time.

It does look like the problem would be either the motherboard or the CPU, unfortunately as you are aware the only way to tell which is the culprit is to swap them out. I don't know where you purchased the parts, but most people will allow you to exchange the components under warranty since you did have it up and running.

[JANINE]

I'm agreeing with Dcc here. It may well be that the problem lays within your motherboard itself.

However i still feel that maybe it could also be the power supply unit itself. Do you have a multimeter? If so set it to measure voltage and place the black probe into the hole or near one of the BLACK GROUND wires (on your 4 pin connector). The red probe should go to the YELLOW 12VOLT wire. You should get a readout of about 12 volts all being well give or take about 5% either way. This will tell you whether or not you have a 12 volt rail out of action.

[asusfrustration]

I have written so many notes to the company etc. that I guess I forgot to mention that it was working. Sorry about that! Unfortunately it broke 1 day before going on vacation so I did not have time to check it out. When I got back it was then possible to start eliminating things eliminate the PSU and switch. Once that was accomplished I realized it was 2 days past the warranty. The company would not allow an RMA. Go figure! Thanks for all the help.

[dcc]

I'm agreeing with Dcc here. It may well be that the problem lays within your motherboard itself. However i still feel that maybe it could also be the power supply unit itself. Do you have a multimeter? If so set it to measure voltage and place the black probe into the hole or near one of the BLACK GROUND wires (on your 4 pin connector). The red probe should go to the YELLOW 12VOLT wire. You should get a readout of about 12 volts all being well give or take about 5% either way. This will tell you whether or not you have a 12 volt rail out of action.

Janine...he has told us that he has tested the PSU with a block tester. If you are not familiar with these they plug into the 20/24 pin connector from the PSU and has a LED display which shows the status of each rail. This may not show the variance that a DMM would, but you don't need that kind of magnification to determine the health of a PSU. Another factor that most people don't take into consideration is that without a load the voltage readings are static and don't really indicate the health of the PSU.

[JANINE]

That's ok. Glad we were of assistance to you.

Btw. What was causing the problem in the end - do you know?

[asusfrustration]

I will be leaving for a vacation in a couple of days so my computer will have to lie there with the guts spread out until I return. When I do I will probably order a new MOBO and I will let you all know what the outcome is. Thanks again

[JANINE]

To be honest Dcc I'm not familiar with Block testers. Can you email me or PM me with a picture of one so I know what they look like please.

Thanks. :)

[dcc]

To be honest Dcc I'm not familiar with Block testers. Can you email me or PM me with a picture of one so I know what they look like please. Thanks. :)

http://www.hardwareinreview.com/cms/content/view/19/