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Fans Run, No Post. Please help.

Last response: in Components
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May 7, 2009 1:47:31 AM

I have a serious problem with my computer. When I turn it on, the case fans power up, as do the HD and DVD Rom, The memory LED's Do not light up, and that's the extent of what the computer does. No post, no beeps, no error beeps. It does this regardless of what peripherals I have installed.

I have replaced the mother board, the power supply, and the processor. I've also taken the motherboard out to make sure there was no short caused by the case. The ram works fine on another computer, and it happens with or without the video card, ram, Hard Drive, CD etc.

I can't tell you how important it is that I get this PC running. I'll list the hardware below.


Motherboard: ASUS A8N 32 SLI Deluxe
AMD 2.8 GHz 5400 Processor
2Gigs Corsair Memory
SATA HD
Nvidia 7900 GTX Video Card

This computer was originally a Socket 939 with a 4800+ processor.

I originally thought it was the motherboard, it has been replaced twice.

The last thing I did on my pc was playing WoW, and it froze up in the middle of the game, the frame buffer stuck on the last frame it displayed. The PC would not turn off. The only signs of trouble before that was random trouble booting. It would do exactly what it's doing now, just the fans running, and I could let it sit awhile. and eventually I could turn it back on and it would work.

Please help, I've tried everything I know and my future depends on this computer running.

More about : fans run post

May 7, 2009 2:43:47 AM

Just checked the cpu support list at ASUS,,that mobo is a 939 it only goes to AMD 6400x939 the 5400 is a am2 cpu,,non???:) 
May 7, 2009 4:20:30 AM

I'm sorry, I totally screwed that up.

I originally had the A8N 32 SLI DELUXE and I replaced it with a M2N 32 SLI DELUXE.
I also replaced the 4800 Socket 939 with the 5400 AM2
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May 7, 2009 4:43:37 AM

The same thing happened to one of my computers a few days ago, everything ran and lit up, but no post. Turns out I fried the motherboard and had to replace it :/ 

Moral of the story: don't ever work on a computer without static protection.
a c 144 ) Power supply
May 7, 2009 3:57:34 PM

What were the original and replacement power supplies? Here's the really bad news. You could have received a DOA replacement PSU (depending on quality, quite likely) or motherboard (possible).

First, about power supplies (part of something I wrote on another thread):
...
There's a rocker switch (that's what they are called) on the back of the PSU. "O" down, it's off. "I" down, it's on. When it's on, a small power supply inside called the "Standby Power Supply" is on. This is what turns on any LED's on the motherboard even when the computer is off. Unfortunately, this does not mean that the PSU is good and you have power going to the motherboard. This little power supply is completely separate from the main circuits that actually power the computer.
...
If you have a multimeter, you can do a rough checkout of a PSU using the "paper clip trick". You plug the bare PSU into the wall. Insert a paper clip into the green wire pin and one of the black wire pins beside it. That's how the case power switch works. It applies a ground to the green wire. Turn on the PSU and the fan should spin up. If it doesn't, the PSU is dead. If you have a multimeter, you can check all the outputs. Yellow wires should be 12 volts, red 5 volts, orange 3.3 volts, blue wire -12 volts, purple wire is the 5 volt standby. The gray wire is really important. It sends a control signal called something like "PowerOK" from the PSU to the motherboard. It should go from 0 volts to about 5 volts within a half second of pressing the case power switch. If you do not have this signal, your computer will not boot.

Unfortunately (yes, there's a "gotcha"), passing all the above does not mean that the PSU is good. It's not being tested under any kind of load. However, if it doesn'tdo all that, it is dead.


Here's some troubleshooting ideas:

Disconnect everything from the motherboard except the CPU and HSF and case power switch. Boot. You should hear a series of long single beeps indicating memory problems. Silence here indicates, in probable order, a bad PSU, motherboard, or CPU - or a bad installation where something is shorting and shutting down the PSU.

To eliminate the possiblility of a bad installation where something is shorting and shutting down the PSU, you will need to pull the motherboard out of the case and reassemble the components on an insulated surface. This is called "breadboarding" - from the 1920's homebrew radio days. I always breadboard a new or recycled build. It lets me test components before I go through the trouble of installing them in a case.

It will look something like this:
http://www.tomshardware.co.uk/forum/page-262730_13_0.ht...
You can turn on the PC by shorting the two pins that the case power switch goes on.

If you get the long beeps, add a stick of RAM. Boot. The beep pattern should change to one long and two or three short beeps. Silence indicates that the RAM is shorting out the PSU (very rare). Long single beeps indicates that the BIOS does not recognize the presence of the RAM.

If you get the one long and two or three short beeps, test the rest of the RAM. If good, install the video card and any needed power cables and plug in the monitor. If the video card is good, the system should successfully POST (one short beep, usually) and you will see the boot screen and messages.

Note - an inadequate PSU will cause a failure here or any step later.
Note - you do not need drives or a keyboard to successfully POST (generally a single short beep).

If you successfully POST, start plugging in the rest of the components, one at a time.

Hope this helps.



May 7, 2009 6:09:11 PM

I've tried all of that except the paper clip thing.
The old power supply was a 530 watt Master Power and the new one is a 450 watt BFG GS series. The thing doesn't beep at all regardless of what hardware is in it.
January 3, 2011 10:18:23 PM

Im having this same issue.
!