PC reboots if someone walk by

Darryl Licht · 26 Feb 2010

That's a micro speaker for the BIOS.

I thought you said that voltage had to be 2 volts, sry!

Dwarf · 26 Feb 2010

Motherboard link for reference: GA-790XTA-UD4 (rev. 1.0) - GIGABYTE - Product - Motherboard - Overview

Darryl Licht · 26 Feb 2010

drarf... some cases come with them instead of the 2" paper cone speaker.

churin · 26 Feb 2010

Dwarf said:

No, that voltage level is OK. It has to remain at a value that is less than the threshold of 2.0V in order for your PC to operate. To check this, power down your system so that it is on standby and connect a multimeter as described above to the appropriate pins. What voltage reading do you get? Now power up your system. What is the reading now?

I assume this is about the voltage between pin 15 and 16. The voltage changed from 0V to 4.2V when the system was Shut Down or let go to Sleep mode.

This image is taken from one of your images. What is the item that I have ringed? It seems to be obstructing the front panel connectors. Also, route the main power harness away from the board so that it doesn't press down on it.
Attachment 56894

That is a ceramic beeper. The main power harness does not really press down on the mobo. I attached some more pictures below:

Dwarf · 26 Feb 2010

OK, that shows that area more clearly. What I suggest is that you temporarily disconnect all connections except for the power and reset switch. Do you still get the resetting? Now, swap the switches. Any change? If you no longer get the resetting, add one connector at a time and retest. What I am trying to do is to eliminate the possibility of cross-talk between the leads. You could also try using a ferrite core around the offending lead(s) to see if that makes any difference.
Amazon.com: Ferrite Core 1/4" Cord Noise Suppressor: Electronics

churin · 26 Feb 2010

I think I already did that as stated in one of my former posts except that about ferrite core. I will go and get it at my local pc shop tomorrow and post back the test result.

churin · 27 Feb 2010

The ferrite is found not available locally so it will take several days to get it from Amazon.

Dwarf · 27 Feb 2010

It's worth a try, but no guarantees. I must admit that I am a little bit stumped by this as it is a most unusual problem.

Romulinx2 · 27 Feb 2010

Hi, have you checked for stray strands or just one strand of wire sticking out where the reset switch is connected to mobo. It could be touching something?
Also check the main power supply cable from your wall socket, it could be a loose wire?
If connected to a filter after the main socket check for loose wires also.
If you haven't got a filter it could be transient/spikes in the voltage from the main power supply in your home.

Hope this helps? :)

Jonathan_King · 27 Feb 2010

Dwarf has asked us for more help, so let me throw in my suggestions. First, try reading these links.

http://www.videohelp.com/forum/archive/pc-reboots-if-i-touch-the-case-t331802.html

http://www.daniweb.com/forums/thread15060.html

I have been watching this thread since it was created, so rather than suggest what has already been tried, let's try another tactic.

Remove all hardware from the motherboard. DVD drives, video cards, hard drives, etc.

Actually, to make this as fail-proof as possible, remove the motherboard from the case as well.

You can leave the CPU and RAM attached to the motherboard.

Then put it back together. Use onboard graphics, keep all USB devices unplugged, and only leave 1 hard drive, the mouse, and keyboard attached.

See if the problem persists.