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I'm having strange PC issue: When i'm turning my PC on, it doesn't send signal to display. All fans are working. There is no sound signal from bios, also HDD loading led doesn't do anything. There is 1 led indicator on the rear side of power supply: it turns to green when pc is on. But in my situation sometimes after 5-10 seconds turning on PC it turns to the red light, and pc shuts down. Tried followings:

  • Tried to turn on with first RAM module, and second one by one. Same problem occured
  • Tried to to reconnect all hdd connector. Still no success

Any suggestions on how I can diagnose and fix this?

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how old is the system? –  Journeyman Geek Oct 22 '11 at 12:06
    
2-3 years. Is that makes sense? –  Tural Aliyev Oct 22 '11 at 12:08
    
makes some things less likely. capacitor plague and bios battery failure is likely, the former cause the issue that cause it was fixed to a large extent, the latter cause those batteries last longer than that –  Journeyman Geek Oct 22 '11 at 12:09
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2 Answers

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The very first thing i'd try doing is swapping the PSU with a known good one - that sounds like the Power Supply is detecting something is wrong and shutting itself down .

While the system is opened up, check for any capacitors covered in gunk like this enter image description here - its unlikely, but easy to check for.

If that fails, try the ram sticks on another box to rule out failure - which leaves the CPU and the motherboard as the only parts that could cause a problem, and those are the most expensive parts to replace.

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the problem is i have no "another pc")) –  Tural Aliyev Oct 22 '11 at 12:16
    
@Tural then how are you talking to us? :p –  Simon Sheehan Oct 22 '11 at 12:19
    
this is what it looks like for an aluminum electrolyte capacitor with no sleeves (the picture above has the same type of capacitors but with sleeves) –  XXL Oct 22 '11 at 12:20
    
@SimonSheehan it's laptop –  Tural Aliyev Oct 22 '11 at 12:22
    
If you can't swap out potentially problematic parts, its fairly hard to actually troubleshoot a non booting system. I tend to swap out the PSU first cause i usually have spares, and its one of the cheaper things to test. –  Journeyman Geek Oct 22 '11 at 14:45
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It could be a problem with blown up capacitors (electrolyte leaking) - inspect your motherboard and vga for damaged caps. Or a problem with your PSU alltogether. As hardware ages - overheating causes electrolyte capacitors to burst which leads to the development of pulsations that could damage particular circuity elements. Google pictures of such if in doubt.

It could also be just a problem with corrupted CMOS data. Have you tried clearing it? There's usually a jumper on the mobo or even a button these days. Consult your motherboard's manual for that. Sometimes, just clearing CMOS does not help. Then, you need to disconnect your PSU from the electrical outlet and remove the battery that is powering the CMOS microchip in order to reach a positive result. Google it, if unaware.

Of course, the most efficient thing is to just cycle every component exchanging it for a known working part - this way you can clearly pinpoint the problem, but it's a time-taking procedure and unacceptable most the time, as spare hardware parts are not available.

For now, just disconnect every other external piece of hardware to a stage that can allow a bare minimal boot (disconnect the HDD cable/power plug, CD/DVD-ROM drive, USB cables, etc). Leave only a PSU + MOBO +1x RAM module + VGA + CPU + CPU HSF plugged. Try booting.

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what is PSU, CPU HSF? –  Tural Aliyev Oct 22 '11 at 12:08
    
Power Supply Unit, processor's HeatSink-Fan (radiator + fan) –  XXL Oct 22 '11 at 12:10
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