PC reboots if someone walk by

[Dwarf]

I mentioned the PSU tests because I was interested in whether the required voltage levels deviated from the nominal values when the system reset itself.

 

[churin]

What case? contact the manufacturer... tell them you have a bad rest switch or wire harness... they should send you a new one. How old is case?

It is a computer case which I bought at a local computer shop about 40 days ago. So it's too late to return it to the retailer. The vendor may agree to replace it with another same model but I am not sure that would solve the problem, because I do not know what the cause of the problem is. Is it the mobo, the PSU or the case? Maybe this particular mobo is just not compatible with this case. Since I tested the hardware system without using the case as mentioned in my previous post, I am pointing to the case which being possible culprit.

 

[churin]

I mentioned the PSU tests because I was interested in whether the required voltage levels deviated from the nominal values when the system reset itself.

How can I access to those test points? It appears there is no way to do so.

 

[Dwarf]

It involves a technique known as back-probing. Essentially, you probe the connections from the back of the plug (where the wires come out). See here for an illustrated description (scroll down to Measuring Voltage).

InformIT: PC Repair and Maintenance: In-depth Look at Power Supply > Power Supply Troubleshooting

 

[Darryl Licht]

Yeah Dwarf... it could be a low voltage/high voltage issue! Eliminate possiblities and test this.

As for testing the voltage churin, make sure you use a good DVM (digital volt meter) and use the blk probe to any blk wire (gnd)... the red probe down the wire whos voltage you want to measure from the back (while plugged in and on of course).

Oh yeah... if the DVM has several voltage settings keep in mind you should expect to find most voltages in the 3-13 volt DC range <--- set your dvm accordingly!

 

[Dwarf]

Another question. Did the case come with a PSU included? In many cases these are of inferior quality. Many people, including Scott Mueller (of Upgrading and Repairing PCs fame), recommend replacing these units with more reliable ones.

 

[Darryl Licht]

I taught A+ for years... always loved the Scott Mueller series! A great resource!

I agree with you again... a good quality power supply is crucial to all my builds, whether a workstation or gaming rig.

What is the make and model of your PSU churin?

 

[churin]

Dwarf;

I measured those voltages as follows:
Pin 7 - Pin 8: 3.7V and stayed unchanged with reset by electrostatic discharge.
Pin 15 - Pin 16: 0V and stayed unchanged with reset by electrostatic discharge.

The PSU did not come with the case. It is BFGR550WGXPSU

 

[Darryl Licht]

Sounds like 15 & 16 are giving a bad voltage... 0 vdc.

 

[Dwarf]

@Darryl:

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?

@churrin:

The PSU sounds OK, and the voltages are within the required tolerances.

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.

 

[Darryl Licht]

That's a micro speaker for the BIOS.

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

 

[Dwarf]

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

 

[Darryl Licht]

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

 

[churin]

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.
View 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]

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]

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]

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

 

[Dwarf]

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]

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]

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.