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Faulty Motherboard or PSU?

1K views 15 replies 3 participants last post by  Tumbleweed36 
#1 · (Edited)
Just built a new computer, but it doesn't work. Everything powers on, but I first notice that I get no display. Graphics card (ATI Radeon HD 4850) might be faulty I thought. I stick it in my other computer and it works perfectly fine, so we can rule that out. The graphics card shows 2 red lights on it btw, which usually indicates it's dead, but it's not in this case. I realize there is no post, no beeps, doesn't seem like much is going on. Could it be the motherboard? The red lights on the graphics card could also mean that it's not getting power. Faulty power supply (Corsair 550W)? Which is it? I wish I had an extra PSU to check, but I feel it is too much of a hassle to pry it out of my other rig. Anyone have any ideas? I used an old hard drive by the way, but it turns out that is dead, confirmed. It should STILL at least boot up right? Is it possible that these things could be messed up even though they are brand new?
 
#2 ·
First of all, I would not run that video card without something like 650 Corsair in there, but don't know if that is the issue.

When one doesn't even boot up, then it normally is time for a bench build. (yes, it is a little work, but worth the effort when you get it going)

Bench Test Your System

BTW, many of our Hardware Techs build their own rigs like this out of the case before we put them in the case. Good way to test as you go before you do all the work of putting it in the case.
 
#4 ·
The point is starting with the absolute minimum components needed to achieve the first post. If you get that, then you can
add in a bit at a time. It also eliminates case shorts from the
equation.

btw, did you clear the cmos on the new board, some boards need
that done before posting the first time.
 
#5 · (Edited)
I'm not sure as to how to clear the CMOS, I'll read up on that. So I tried the bench test and still no post. The graphics card actually turns on now though! The fan starts spinning, no red LED fault lights, but after a few seconds will just stop. No beeps. Is http://www.newegg.com/Product/Produ...er+Supplies-_-Corsair+Memory++Inc.-_-17139004 really not strong enough for a HD 4850? I would think it should at least boot! Could it perhaps maybe even be the CPU?
 
#8 ·
I use this heatsink and the paste that came with it: http://www.newegg.com/Product/Produ...CPU+Cooling-_-Zalman+Tech+Co.++Ltd-_-35118223.

Also, the CMOS reset WORKED in bench test. I was able to access the BIOS and there was display and everything.

I decide to put it back in my case, and now it doesn't work again. Then I tried taking out a stick of RAM, pressing the power switch, and everything either turns on for less than half a second or doesn't turn on at all. I think I might have just messed up my power supply.
 
#9 · (Edited)
It sounds like you have a grounding issue with your case/motherboard standoffs. I don't think you have harmed anything at this point, but one never knows for sure. My money is on the grounding issue and that is why it worked out of the case, but not in.

Does your case have actual standoffs or those little nipples that stand up from the case? Remember, one screw for every hole and one hole for every screw....usually nine...no more, no less. If an extra standoff is in there or one of those nipples touches where it should not, it will shut down when it grounds.
 
#10 ·
Yeah the case had risers. I'm a little worried about the PSU now though. I really think I killed it already. I took it back out of the case into bench test mode. No dice. When I press the power button, i hear a little buzz from my power supply, then nothing happens. :sigh: Just when I can finally get a post this has to happen!
 
#11 ·
Is anything blocking the fan in the power supply? Makes a hum if the fan is stopped. The psu does have short circuit protection, which is why it shuts down when there's a short. Try the cmos again. You may be to the point where you're going to need to borrow a psu for testing.
 
#12 · (Edited)
Is there a reset button on that PSU, some do have that?

Unhook it completely and let it set for a few minutes and then try it again.

Check those fans, make sure you didn't bump the 120/240 button on the back of the power supply (some have those) to the wrong side.

Make sure the off/on button which many have is turned on.....on the back of the supply.

Check that the wall outlet is working properly.

Remember, that power supply has to be hooked up to something to work, so test it while it is connected to the motherboard (not grounded, I hope).
 
#13 ·
Alrght I'm not sure why, but just like you said, the power supply decides to magically work again after a few hours of cooldown. Now I am able to post again! Before I put this back in the case though, can you guys warn as to what else could mess it up? Like why would it work fine in this bench test, but not in the case? Thanks!
 
#14 · (Edited)
The PSU needs to have time to drain some of that (they store power) "juice" stored in those capacitors so the time permits them to cool and drain some. Otherwise, it protected itself from frying the PSU by shutting down.

The issue here (I would almost bet) is the standoffs (nipples) on that motherboard tray. One must be pretty darn careful they don't ground on the motherboard itself. You may even have to (if you can't solve that issue normally), use some small thin fibre washers to insulate that board from the nipples (between the nipples and the motherboard) on that motherboard plate. The screws you put in will provide the necessary grounding that the board does need. The nipples just can't touch delicate components of the motherboard or you are right back where you started.
 
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