Strange problems powering up PC

[sark28]

Hi all,

I built a new PC and have been having a strange problem powering up my system. Basically, I had it up and running but the northbridge temp was running a little hot (47-48 degrees C). So I took out the MB, replaced the northbridge heatsink with a Zalman NB47, and put my system back together. Hit the power button and nothing happened. Fans would not power up, nothing. I verified the PSU still worked by using the paper clip trick to get it to power up by itself (connected green wire to black ground) and the PSU fan powered up ok.

I now have the MB out of the box, and only memory and CPU plugged in just to see if I can get it to power up. It still will not power up. Strangely, if I unplug the power cord, then plug it in, the light on the ethernet jack turns on right away. It never used to do that before - it would only turn on when an ethernet cable was plugged into it, but there is no cable plugged in currently. The light also indicates that the board is getting power somehow at least. But it still won't power up.

If I wait for about 5 min. the ethernet light goes off. Now here's the weirdest thing - if I hit the power switch after the light goes off, the fans start to run! It seems like the PC is powering up normally. Now, though, if I power down, it won't let me power up again until I repeat the process, i.e. unplug, plug back in, wait for ethernet light to go off.

My system is Chaintech VNF4 Ultra, Athlon 64 3500 90nm, Zalman 7000 AlCu heatsink, Corsair Value Pack PC3200 memory with Seasonic Super Tornado 400W PSU.

I'm thinking I might have shorted the MB somehow?

Any help would be greatly appreciated!

 

[montag451]

Hi, Welcome to the forums Sark.

Seems you have done the right trouble shooting methods.

Could you reset the BIOS by taking out the CMOS battery, and unplugging the machine,,,,, or using the CLRCMOS jumper for 20 minutes while the system is unplugged.

Have you got any spares lying around you could try?

 

[sark28]

Thanks for the welcome and the help montag!

I just tried to clear the CMOS by using the jumper for about 1 minute while machine is unplugged. I also put a video card in so that I could see if the board would POST when it powered up.

It would not post. Strangely, it's behaving differently now. It will now power up anytime I hit the switch, and the ethernet jack light doesn't light up any more when I plug in the power cord. But it won't post, and it also won't respond to power down when I hold the power button in.

Ack! This is so weird! Any suggestions? Maybe it's time to RMA the mobo...

 

[montag451]

Ok,

Have you got the case speaker plugged into the header on the mobo?

 

[sark28]

Yup. The only things I have plugged in to the header are the power switch and the case speaker, plugged the speaker in so I could hear a beep if it posted. But no beep...

 

[montag451]

Can you take the memory out next, and reboot

 

[sark28]

Ok, took memory out and rebooted but still no POST. I then removed the video card as well (so only CPU is left) and rebooted but got nothing. Fans power up but no POST.

 

[montag451]

OK,
The only things connected to the mobo are the:
cpu/fan
psu
headers/pwr sw/case spkr

That means that the prob is most likely in, yeah you guessed it....
psu or cpu or mobo.

What psu did you put into the system. Even if you get it to work, it may still have a prob. If it is one that came with the case, then I would definitely change this first if it isn't a known good brand.

 

[sark28]

The PSU I am using is the Seasonic Super Tornado 400W. Supposed to be good PSU I think. I'm guessing its the mobo since the CPU worked fine before and I don't see how I could have damaged it just moving around the MB. But damaging the MB I could see happening.

I'll RMA the mobo and pray the next one works - thanks so much for the help!

 

[montag451]

Good luck.
Will you post back please and let us know.
Dont be a stranger.

ciao