I am creating this topic here because I have found a fresh and very relative discussion here with many useful suggestions.
Here is that thread
In that case, there was a problem with motherboard. I would like to discover what mine is.
The problem: A desktop computer shuts down after arbitrary amount of working time.
Part 1. Purchase.
I have purchased a used computer just about a year ago. When I brought it home, it was working fine till the morning, then just shut himself down. After the shutdown, all USB connected devices and keyboard leds became bliming with about 10 seconds period, during which it is impossible to power it on.
When I have re-connected the power cord the bliming vanished and the PC powered on without even the power button pressed.
But it worked for only several seconds and then powered off himself.
No matter what I`ve tried next, I couldn`t get it working longer than for several seconds. I have removed all of the additional devices installed - DVD-Rom, USB, devices, tried to connect the power jack from another room - same result - power off after several seconds and then bliming.
Bu then, suddenly, it lasted for several hours. After self shut down, another several hours which allowed to perform my daily tasks.
I have then brought the PC back to the sellers next day, they have also disconnected all the additional hardware I have purchased, powered on, loaded the BIOS harware monitor screen and it was working like not going to shut down. I couldn`t even proove it has any problems!! So they said the problem is most likely with the additonal hardware I am using - either HDD, or DVD-ROM or anything else. They have only fixed the power indicator led which was not working.
When I brought it home, it was working well! I have then installed an additional HDD, a laptop 2.5' HDD through a transmitter, connected back DVD-ROM, various USB devices and it was working well with no issues!
The problem just like magically vanished!
I have left the case box opened expeting the issues to appear again.. But they were not appearing.
I have then purchased an additional audio card and it has worked almost with no problems for a year. There were similar problems maybe just a few times but only during some extreme overload usage, so it was acceptable for me.
Part 2. 1 year after.
Now, exactly 1 year after, the problem started to happen again! But this time I have noticed that the PU fan became very noisy. It was easy for me to detect as the case was still opened. I have cleaned up all the dust from mostly everywhere and it became working better, for longer periods of time.
As the PU fan became noisy again, it started to power itself off more frequently and I have opened the power unit to clean up itself from the dust and especially the fan.
But it has not fixed it. I have noticed that the noisier the fan gets, the faster power off becomes. I have stopped the fan with my fingers and the power off almost immidiately appeared.
I have conluded that this is all because of the PU fan. Then I have put it on the very "easy" condition to let himself run as more smoothly so that I could at least boot up and send the important emails. It worked.
Part 3. Fixes and the current state.
The next day I've brought the PU to the market, aiming to buy a new fan and expecting all my problems with power off to get solved. But it appeared to be enough to only put some oil inside of the fan and get it working properly!
Feeling very happy about it I have put the PU with its fixed fan back and closed the case of the system block. It has worked then only for several hours before the self power off. I have decided that it`s an overheat as the case is closed, the heat rises. So I have purchased a "chassy fan" and had it installed on the system block.
It did not help, the poweroff still constantly happened after several hours of use.
Then I have opened the case, loaded up and decided to install some temperature diagnostic programs. Under Linux. It happened so that this "sensors-detect" utility was taking about 100% of CPU during the detection process of the sensors supported. And the computer was shutting himself down exactly somewhere in the middle of the scan process.
Having the case opened, I have installed back the chassis fan, having as much cooling as possible. The detection process went fine now and completely, but it has failed to work... That`s some Linux software related issue.
So I decided it`s an overheat problem. But after leaving the PC to work for night, today in the morning I have noticed it powered himself off and all the USB devices where bliming as it usually happens.
And now, when the power off happens, it gets it really hard to get back working for at least a hour. No matter what I try - disconnect power cord and wait, disconnect memory.. still works only for several seconds and powers himself off.
After about 10 tries of such a behaviour it finally starts to work for long.
Now I have been able to boot up, find the above mentioned thread, register on the forum and exactly after forum's congratulation mesasge, it powered himself off!
Then I had to again boot for like 10 times until it would became working notically stable and works now as long as I could type this message!!
Computer seem to power him off contantly during the overheat. But getting him back on takes about 10 tries.
Computer also powers off totally unexpectedly without the overheat during several minutes / hours of work.
When I was having my PU fan being fixing, the guy also replaced the bloated condensor within the PSU.
In the mentioned thread, someone suggested that a bloated condensor with + mark on top somewhere on the motherboard could be the issue. I have found so far 2 bloated condensors, exactly the same as the one the guy have replaced in my PSU. But they do not have the + on the top, but a triangle sort of a sign, and they are standing together and bigger than those with + on top.
I am magically able to write this message without interruptions.. and hoping to get the great suggestions so that I can go tomorrow to the repair market with good results.