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Mysterious no signal...

Last response: in Systems
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September 6, 2010 6:16:05 PM

Hey guys.. and girls :p 

I wanted to get peoples opinions on my mysterious no signal from my monitors... I woke up one morning and went down stairs to turn my PC on, unfortunatly when I did it booted up fine, from what I could hear the fans where spinning but there was no display. I took a closer look in my system and noticed my 260GTX fan had stopped spinning and it had become very hot, I took it out of my system assuming it was the cause of all my pain and sent it off to get replaced on my warrenty.

Three weeks later I started to become inpatient to play Starcraft II so decided to lend a graphics card from work until mine was returned. I got home all excited to be able to have my PC back only to find my display still didn't work, even with the new graphics card.

I removed everything and started from the top, but found it strange how my motherboard does not beep at all. Even with no memory in, I checked the small speaker attachment seeing if I had got the minus and negative mixed up. But still no noise...


This then made me think, crap... its my motherboard as well, there must have been a power surg to damage both my motherboard and graphics card! Low and behold I had only recently upgraded so quickly set up my hardware on my old motherboard. Finally, I would have my PC back!

It did the same thing...

Now I'm completely confused, if its not my motherboard which is causing this issue, I have rotated my memory. It must be my PSU or CPU? The problem is, which one do I send back saying its broken?

Also one thing I found strange is the sound of my system as it boots up you get used to the up and downs in speed of your fans when booting up. With everything attached the fans sound very much like its booting into bios, checking drive priority and then speeding them up again as it loads windows. Giving me the impression its still working, just not displaying? This gives me the impression its my PSU, but could a PSU ever cause such a display issue?

My 260GTX requires direct power cables from my PSU, but the 9800GT I borrowed from work does not?

Life fails at times!

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September 6, 2010 6:42:51 PM

I would suggest you test the PSU, as its most likely the culprit. If you dont have another machine available, follow this:

Quote:
"The best way to check the PSU is to swap it with a known good PSU of similar capacity. Brand new, out of the box, untested does not count as a known good PSU. PSU's, like all components, can be DOA.


Next best thing is to get (or borrow) a digital multimeter and check the PSU.


Yellow wires should be 12 volts. Red wires: +5 volts, orange wires: +3.3 volts, blue wire : -12 volts, violet wire: 5 volts always on. Tolerances are +/- 5% except for the -12 volts which is +/- 10%.


The gray wire is really important. It should go from 0 to +5 volts when you turn the PSU on with the case switch. CPU needs this signal to boot.


You can turn on the PSU by completely disconnecting the PSU and using a paperclip or jumper wire to short the green wire to one of the neighboring black wires.


http://www.youtube.com/watch?v=5FW [...] tube_gdata


This checks the PSU under no load conditions, so it is not completely reliable. But if it can not pass this, it is dead. Then repeat the checks with the PSU plugged into the computer to put a load on the PSU. You can carefully probe the pins from the back of the main power connector."
September 6, 2010 7:10:48 PM

Thanks for the help! I think I would kill myself putting paper clips into anything related to electricity, but will take it into work with me tomorrow and get our IT department to test it for me. See if caput! Fingers crossed it is, as the sooner I find out the sooner I can play Starcraft II!
September 8, 2010 6:28:56 AM

It was the PSU! Never would have thought it, tried it on another machine yesterday and had no display using mine and everything was fine using an alternative. Thought I would post this incase anyone runs into a similar problem and picks up this topic on google search!
!