Fans run and CD-ROM light flickers when MB powered off

[smcguire36]

I recently replaced my ASUS A7N8X-Deluxe motherboard that was fried with another Asus motherboard (an A7V600 motherboard). I have assembled MANY Athlon-based PCs over the years.

When I plugged the PC in for the first time, the fans started up on their own (without pushing the power button). Also, the lights on the front of the DVD and CD drives started flickering also. This was something new for me and I don't know why it is doing this. When I power up the PC, it booted just fine and works fine when running. I just need to find out why the fans and drive lights are on when it is supposedly powered off.

Anyone have a clue? Do I have a jumper set wrong?

--Stewart McGuire

 

[r_manic]

Have you noticed any problems with your PSU? It's possible your first mobo fried because of power instabilities.

 

[smcguire36]

As far as I can tell, the power supply seems to be working fine. I will try a different power supply and see if that makes a difference. Is there anything else I can check while I have the machine torn apart?

My old motherboard ended up with a really weird problem. It would boot into the BIOS and everything would seem to run fine. But if I attempted to boot into an operating system, as soon as the machine got past the BIOS boot option, the keyboard would stop working. It didn't matter whether I used a USB or PS2 keyboard, the results were the same. I know there was nothing wrong with my OS (Kubuntu) as I took the hard drive out and put it in another machine and it booted perfectly. I also had tried booting up a Windows XP CD-ROM and that wouldn't boot either. In both cases, it would get to a point that required keyboard input and just stop, waiting for input but it would never see any input from the keyboard. After several hours of testing, I concluded that the problem was the motherboard and purchased a replacement.

When I can afford it, I will be upgrading this machine to the latest technology with all new components, but that is a little out of price range right now (darn things like food and gas take priority these days).

--Stewart

 

[djbrad007]

Hi,

on most new motherboard when you plug the cord in the psu, it does a self-check for a few seconds, then shut off.

Brad

 

[smcguire36]

This was not a "NEW" motherboard. It is a system pull that I purchased off of EBay (fortunately I didn't spend a lot of $$ on it).

This is not just a brief self-check then shut-off. The fans stay ON all the time (like it thinks it is in standby but it isn't).

- I just replaced the on-board BIOS battery to make sure that wasn't the problem.

- I also purchased an Antec PSU tester and all the voltages are within the normal ranges.

- I rechecked all the jumpers on the motherboard to make sure that something wasn't incorrectly jumpered (they weren't).

I am at a loss as to why all my fans start spinning as soon as I turn on the power supply (from the hardware switch on the PSU). The fans start spinning MUCH faster when I push the soft-power switch and the PC starts booting. No other motherboard I have ever worked with exhibited this behavior.

As an aside, the speakers make a funny popping sound after shutting the PC off (until I turn off the hard-power switch on the back of the PSU). I wonder if these two issues are related.

--Stewart

 

[shortstuff_mt]

It sounds like a short to me. I would try breadboarding the system by building it with the motherboard outside the case on a non-conductive surface. A cardboard box works great.

 

[smcguire36]

Hmm. I never thought of that. Great suggestion. That will be a weekend project. Thanks for the suggestion.

--Stewart