No display signal - is my PSU faulty? \ VOGONS

No display signal - is my PSU faulty?

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First post, by MMaximus

Posted on 2017-03-10, 22:29

MMaximus Offline

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Location: FR

I have been experiencing a strange issue on my modern rig since yesterday - It powers on, the fans start, but there is no display and there doesn't seem to be any boot activity as the HDD led doesn't blink. Keyboard is unresponsive with inability to turn on the leds for num lock or caps lock. I unplugged all peripherals, cleared the CMOS, and since I own another LGA 1150 PC, I swapped video cards, ram, and cpu and still got the same problem. Loss of display signal happens with onboard graphic or with PCIE video card.

I initally blamed the mainboard (ASUS Z97-A) but decided to swap PSUs just in case, and managed to get the system to work. Moreover, when I used the "faulty" PSU to power on the other system (MSI H81M-E34), I got the same problem - system turns on but there is no video and no boot. The PSU is a less than 2 year old Corsair CX 600M.

I guess I always assumed that a PSU failure meant a complete inability to power on, but not something like the loss of video. Have any of you ever experienced a similar problem? Any info would be appreciated.

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Reply 1 of 3, by sf78

Posted on 2017-03-11, 13:55

sf78 Offline

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I had the EXACT same thing happen to me in December. With no previous warning the system just refused to display anything, even though the computer itself seemed to start just fine. I thought the GPU was busted, but got similar results with another one. Then I swapped the PSU and everything worked just fine. I even opened the broken PSU to check if there was any clue to why it failed as it was a pretty beefy one (750W) and I managed to get my system to work fine with a 350W PSU, but a quick visual inspection showed no problems, it looked brand new. At this point I didn't bother checking what had failed as one can easily get a working PSU for pennies, so I just thrashed it.

Reply 2 of 3, by Jepael

Posted on 2017-03-11, 16:12

Jepael Offline

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So it can be started and fans run so it's not completely dead, and there's no smoke of flames.

But there might be one of the voltages (3.3V, 5V, 12V or -12V) completely missing or just out of regulation (too high or too low), so the Power Good signal does not let the motherboard out of reset. Or the voltage monitor fails to measure one of the voltages so it thinks voltages are not OK. Or the voltage monitor fails to drive the Power Good signal.

Just measure the voltages when the PSU is running.

Reply 3 of 3, by MMaximus

Posted on 2017-03-20, 16:51

MMaximus Offline

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Thanks for the replies - I can see I'm not the only one this has happened to!

I don't have the equipment or know-how to test the voltages so I guess I'll apply for a RMA on the Corsair website and hopefully they'll send me a replacement.

In the mean time I have replaced the PSU and the computer now works but I am experiencing another issue which I've posted about on the following thread PSU delayed start - is this normal?

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