I think I blew up

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smeezekitty

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Sep 11, 2012
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I am fairly sure I blew the south-bridge on my HP SR5010NX with Windows Vista and 2 GB ram.

So the story is:
Last week I had an Arduino (Microcontroller development board) connected to the computer.
I then connected the ground of the Arduino to an old oscilloscope which turns out has a fault with the Hot side of the AC line shorted to case.

As soon as I connected the ground, there was a loud pop and a flash and half the room went dark (the USB ground was shorted to the 120VAC mains).
I then disconnected everything and reset the main breaker.

The only casualties at the time was the Arduino and the front USB port the Arduino was attached to. Within 2 days, the other front USB port became intermittent. Then, it failed completely.

Then one of the back USB ports became intermittent before failing completely leaving just one working USB port which my wireless dongle was attached to.

This morning, I brought the computer out of standby but it was not working correctly.
I had no internet connectivity, my mouse was jumping around and the volume icon was crossed out saying "no audio device" and I had a pile of "Program has stopped working messages"

When I navigated to device manager to see what was going on, I got a "Disk read error on drive C" message.

At that point, I thought I should just reboot. I went to the start orb and selected restart.
It shut down as normal but it would not post. The fans revved all the way up and the screen remained black. Shutting it down with the power button and restarting it again had the same result.

I tried no ram and both sticks in both slots with no result.

I felt the Southbridge heatsink and it burned my finger. It is much too hot to touch even with the computer off. I have to unplug it for it cool off.

Do you think that I indeed blew up the southbridge or something else?
 
Solution
groundrat
Unfortunately it sounds like you sent 120VAC through your motherboard. I am guessing you have breakers and not fuses. Fuses usually go a few ms faster. Sometimes a breaker, especially one that has been hit a few times, will hang a long time (electrically speaking) before it trips.

Any time the south bridge is hot enough to burn you, some kind of damage has been done. Are there any telltale LED's or error codes on the motherboard?
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Have you reset the bios? Remove the round board battery for one minute with the power supply unplugged, then replace. You'll know the bios is reset if the fans become louder and the post screen asks you to press an "f" key to enter the bios and save the settings.
 
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Yep. Tried pulling battery and switching the reset jumper with no effect.
 
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Unfortunately it sounds like you sent 120VAC through your motherboard. I am guessing you have breakers and not fuses. Fuses usually go a few ms faster. Sometimes a breaker, especially one that has been hit a few times, will hang a long time (electrically speaking) before it trips.

Any time the south bridge is hot enough to burn you, some kind of damage has been done. Are there any telltale LED's or error codes on the motherboard?
 
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Solution

Absolutely no LEDS.

When I press the power button, the front LED comes on and the FANS wind up near max.
Within 1 second, the harddisk spins up and calibrates as normal. Then the CDROM light flashes and it goes click click then it just holds steady like that until shut off.

From what I read, the southbridge handles fetching of the BIOS code which would explain the failure to post.

There are no beeps on the internal speaker.
 
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I doubt it. It is pretty old at this point. Looks like I will either be looking at a new computer or board.

Thanks anyway. Just wanted to see if there were anything else to be tried and I do not think there is.
 
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Ok I think at this point I will try to replace the motherboard.

I was thinking of an ASRock G41M-S3 because it fits the old CPU socket and seems to support the old 533MHz FSB.

It looks like I will need some new ram because the current sticks are DDR2 and the new motherboard takes DDR3.

One question (or 2):
The motherboard manual (ftp://europe.asrock.com/manual/G41M-S3.pdf) mentions when using 533 MHz FSB, to use 800MHz ram which is quite uncommon now. Can I use 1066 MHZ ram instead?

Also, do any special steps need to be taken with Windows Vista after replacing the motherboard?
 
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