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Why my pc froze after switching the desk lamp or the speakers ON or OFF?

stalker

Sep 28, 2013
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I'd like to know how it's technically possible that in the time period of few weeks my computer reacted to ON or OFF the desk lamp and ON or OFF the speakers. I tried to find an answer in pc forums but nobody could explain this sufficiently so I want to try it here becouse I think it's related even more to electronics forum. I had connected two monitors to the pc and always in the evening (without exception every night for a couple of weeks) when I needed to use headphones and switched off the loud speakers my both monitors turned off (light indicator on both changed the colour from green to orange), the computer froze (caps lock light indicator on the keyboard didn't react) and the fans inside the case spun up to the max speed (I'm not sure if every fan, I only know that a graphic card fan did it). The pc was in this state until I reseted it. Then after rebooting I turned on the desk lamp and the same thing happened again. Before I went to sleep I turned off this lamp and if it was before turning off my pc it happened again.. Then in the morning when I turned on the speaker it happened again.. After that when I tried experimentally to switch on the lamp (which was pretty absurd when it was the light) nothing happened. So I switched off the lamp and it happened again. Together I guess it had to happen for at least 50 times (it wasn't a coincidence happening randomly)... Last time it happened when I returned from outside..it was exactly at the moment when I put my phone on the ground in my room. There wasn't any electronical reason from my side. Now it's alright. It stopped spontaneously without any intervention even I didn't change anything around my pc.

I had everything plugged into one power strip but I could run two pcs together there and it worked fine and the freezing thing was happening when I ran only one pc. That means that there was a reserve in power for higher load. So I think it wasn't the problem with low power from the wall. The desk lamp was with 11W fluorescent tube and was plugged into the wall (same the speakers). I'm sure it was happening even I didn't have anything else plugged into the same power circuit.

I have my pc still connected to the same power circuit (using the same power strip) and I have no problem anymore. Also the power supply still works fine in my pc.

I'm just curious how it is possible that my computer reacted this way.. What is the electronical bond between the lamp or the speakers and the pc? What could be the cause of starting the problem and stopping it? Thanks for any ideas.
 

Harald Kapp

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My guess is that the power supply of your PC is very sensitive to EMI (electromagnetic interference). Whenever you turn on or off another device that is connected to the same mains outlet, the mains voltage will see a short drop or a spike on top of it. This may disrupt the operation of the controller in the PC's power supply.
After resetting the PC the controller resumes normal operation and everythingis fine again.

Can you tray to change the power supply? Or just connect the PC to another outlet.
 

stalker

Sep 28, 2013
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My guess is that the power supply of your PC is very sensitive to EMI (electromagnetic interference). Whenever you turn on or off another device that is connected to the same mains outlet, the mains voltage will see a short drop or a spike on top of it. This may disrupt the operation of the controller in the PC's power supply.
After resetting the PC the controller resumes normal operation and everythingis fine again.

Can you tray to change the power supply? Or just connect the PC to another outlet.

Thanks for your comment!

The thing is I can't try anything now because I'm not having this problem anymore.. I'm just curious about how it could be caused.

You say that voltage fluctuation caused by turning another device on or off can cause a fail inside the power supply...It sounds reasonably. But I don't understand fact that the same power supply still works fine. If it was so sensitive why I'm not still having the same problem? So It means it couldn't be caused by failure of power supply, doesn't it?

Another thing is the reaction of the PC. When you said "disrupt the operation of the controller" it means that power supply was sending wrong voltage to the PC? During a drop of voltage I would expect reset or shut off and not so complex reaction (turning off the monitors, freezing and speeding the fan of a graphic card up to max). Only that a graphic card has some safe mode for that case (I presume that a graphic card is the component which can turn off the monitors or speed up it's fan) and these steps were programmed in the graphic card as a reaction for the wrong voltage from the power supply. I just don't believe that so complex reaction could be caused only by wrong voltage.. or could?

And last thing - it seems strange to me that drop (turning on devices) and surge (turning off devices) of voltage could have the same effect. I would expect a different reaction for each case...

Does anybody have some more ideas or comment?
 
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Harald Kapp

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This kind of temporary failure is particularly hard to debug.

Some possibilities are:
- a loose connection within the power supply
- a weak solder joint
- some temperature dependence

What has changed from the time you observed these failures and now? Hot or cold weather? Dry or humid air?

I would expect reset or shut off and not so complex reaction
A PC is a very complex circuit. An apparently simple power supply (PS) not less. A runaway controller within the power supply could generate all kinds of failures. From a total fail of the PS to generating voltages just a bit off the nominal value, but enough so to disrupt operation of the PC. I think your reasoning about the graphics card is good. The card possibly was reset, turning off the video output and turning up the fan. If the graphics card got locked in that state, but the mainboard was not affected, there was no reason for the whole PC to reset. If you observe this behavior next time, have a look at the graphics card. Does it sit snuggly in the mainboard connector? Are any possible additional power supply connectors firmly attached to the graphics card and do they deliver the correct voltage?

it seems strange to me that drop (turning on devices) and surge (turning off devices)
For one I didn't necessarily mean that both effects are at work. It could have been either of the two. Secondly: yes both could have had such an effect. If a component is operated outside its nominal range, be it below or above, the component's bahavior is unpredictable.
 

stalker

Sep 28, 2013
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What has changed from the time you observed these failures and now? Hot or cold weather? Dry or humid air?

Your answers seems to be much better than those I got before on other forums so thanks..

It's quite long time when I had these problems (three years ago).. It crossed my mind just now that I'd actually like to know how it could be caused. It was happening in August maybe for two or three weeks and never again since then. So I think things like weather won't be the issue here because it doesn't repeat anytime during whole year.

I can believe in explanation you brought (in combination with a graphic card mode) but only mystery is the cause of starting and stopping it.. Because it probably won't be happening ever again unfortunately it will remain unexplained.
 

WaterWalker

Sep 21, 2013
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Hi Stalker

The guys here have given a pretty good explanation of might have happened. But I just wanna share a similar experience of mine to see if it wasn't maybe a factor as well.

A friend of mine also had a problem of his PC freezing when he tried to play a game, or run a graphic intense program. He had a big enough P.S.U. to run everything in his PC. But, he made a small error. His graphics card had the same power connector as a normal hard drive. And, what he did was connect the hard drive and the graphics card to the same power line. This meant that when the graphics card was used to full potential, and thus drawing more power, it would siphon off power from the hard drive. This meant that the hard drive couldn't perform it's duties and the PC froze.

I don't know what size P.S.U. you had, but you did have two screens connected to the pc. That would have made the graphics card draw a bit more power.

But this is just something I saw in another pc. Still don't know why, if the P.S.U. was strong enough, it would that.

Could this maybe have been a scenario in your story?
 

stalker

Sep 28, 2013
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Hi Stalker

The guys here have given a pretty good explanation of might have happened. But I just wanna share a similar experience of mine to see if it wasn't maybe a factor as well.

A friend of mine also had a problem of his PC freezing when he tried to play a game, or run a graphic intense program. He had a big enough P.S.U. to run everything in his PC. But, he made a small error. His graphics card had the same power connector as a normal hard drive. And, what he did was connect the hard drive and the graphics card to the same power line. This meant that when the graphics card was used to full potential, and thus drawing more power, it would siphon off power from the hard drive. This meant that the hard drive couldn't perform it's duties and the PC froze.

I don't know what size P.S.U. you had, but you did have two screens connected to the pc. That would have made the graphics card draw a bit more power.

But this is just something I saw in another pc. Still don't know why, if the P.S.U. was strong enough, it would that.

Could this maybe have been a scenario in your story?

Hi WaterWalker,

I don't think I had same scenario as you described. My pc reacted to manipulation with a desk lamp or speakers.. not to starting any applications and causing higher load.

In your friend's case there could be overloaded a particular power line. I think each power line has its max output for itself and the complete output of a PSU is a sum of those outputs from each power line. In other words you can't take all the output of a PSU only from the one power line. I'm not sure but I think it could be this way.



The only thing I'd like to know is what caused starting and stopping my problem with freezing, turning off monitors and speeding the fan up to max? I didn't change anything and the problem came for two or three weeks (and moreover it wasn't a coincidence happening randomly) and then disappeared. If anybody has an idea please let me know..
 

stalker

Sep 28, 2013
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One last thing: please if anybody know about somebody having same problem (it doesn't matter if in past or now), let me know and write about it here. I'd really like to know how common or rare it is...
 
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