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A8N-SLI Premium & SE Wont Post - CMOS Batteries Dying

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July 8, 2012 4:43:40 PM

The other day one of my computers with a A8N-SLI Premium mobo simply died and wont come back on. When I flip the power switch on the back of the box, the fans (including CPU) and everything in the box come on, but the mobo never posts. No video, no beeps, nothing. CD player wont open if it is connected to the mobo - I believe again b/c the mobo hasnt posted. This mobo is supposed to have audio messages for a failed post, but I'm not getting anything there either (I plugged in amplified speakers to the green audio out port). Only way to turn the machine off is to turn the PSU off - the power button does nothing, no matter how long I hold it. Replaced the CMOS battery and reset CMOS, still nothing. I did some searching around the net and found posts saying to strip the system all the way down to the mobo and CPU (with cooler), outside of the case. Did that, still nothing. People were saying that if the CPU was bad, the mobo should be telling me that, but it wasnt. Also, I tested the PSU using a multimeter, and it all checks out great. Thus, it seemed like only 2 components to pick from, and I figured the mobo was bad.

So I ordered a "new" A8N-SLI SE mobo from ebay. First thing I notice is that the mobo must not be actually new - I see some thermal paste on the white part of the CPU socket. Also, the CMOS battery came 100% dead according to my multimeter, which correctly reads a new CMOS battery @ 3.3V. Well, I decided to give it a shot anyway (with a new CMOS battery). Plugged in just the CPU (and cooler), outside the case. Flipping the PSU on, the mobo still needed me to jump the two "power on" prongs on the mobo to start it up, as expected. I did that, and to my joy I got a single beep out of the MOBO as it tried to post. Thinking it was odd that I didnt get more beeps (no memory, no VPU), I turned it off by cutting the power on the PSU. Started putting things back into the case, and before I got too far I tried firing it up again. Now when I flip the PSU on, the mobo comes right on w/o jumping the "power on" prongs b/c of the "restart on power failure" "feature" apparently. No big deal, except now its acting exactly like the other mobo. No beeps, no POST, power button will not turn the machine off. Pulled it all back out of the case, removed everything but the CPU to match my first test. Same thing - no beeps, no POST.

Is this a cut and dry case of "the CPU is bad"? Or am I missing something? I thought for sure, based on my tests of the first mobo, that the mobo was to blame. Now I'm not sure since the new mobo doesnt work either. However, the new mobo has me wondering, b/c I could tell that it was not actually 100% new, and the CMOS battery came 100% dead.

Adding to the variables here, I experienced something very very strange with the CMOS batteries. When testing the first mobo, one of the things I tried was replacing the CMOS battery with a new one, which I verified at 3.3v using a multimeter. Well, when I got the new mobo and noticed that the CMOS battery on that one was dead, I first pulled the new battery I put into the old mobo. Much to my chagrin, the battery was showing only 1.6V on my multimeter. So I purchased another new battery, and it showed at 3.3V as expected, so it's not a prob with the multimeter. So I put the new battery in the new mobo, and it was in there as I tried to get the new mobo to post/beep at me a few times. After each time where I turned on the PSU and fired up the mobo, when I pulled the battery out and retested it with my multimeter, the battery lost .02-.03V of charge. In just a few tests, it went from over 3.30 to under 3.20. So it's like when the mobo is running, my battery is being drained. What would cause that?

I'm just so confused/frustrated :( . I know this post is huge, but I wanted to answer as many questions as I could before they are asked. Any insight would be much appreciated.

Thanks!
-Brett
July 31, 2012 7:08:17 AM

Problem ended up being a bad PSU, which took both the first MOBO and second MOBO down with it. Purchased new PSU, and new MOBO, and the machine is back up.

Can someone please explain to me why no one even took at shot at helping with my problem? Was my initial post too long?
August 18, 2012 5:22:27 PM

HitmanInWis said:
Problem ended up being a bad PSU, which took both the first MOBO and second MOBO down with it. Purchased new PSU, and new MOBO, and the machine is back up.

Can someone please explain to me why no one even took at shot at helping with my problem? Was my initial post too long?


I have the same problem. I tried another PSU but I am not sure whether it works. Still no post. I have exactly the same issue and will try another PSU. I'm keeping my fingers crossed...
!