PC won't post after power outage - PSU seems fine

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aotengs

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Aug 29, 2013
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Hi,

Recently we've had a power outage in one half of the house. Now two days later my computer won't start up when I press the power button. When I press the power button absolutely nothing happens - no beeps, no lights, no fans, nothing. I have also tried resetting the CMOS battery using the CMOS jumper to no avail.

This is actually the 4th time this has happened. Each time it seems it happens a short while after a power outage occurs. I don't think it is to do with the PSU because I RMA'd my old PSU the last time this happened and this current PSU is only a few months old - the same problem occurred with the last PSU as it does with this one now. Sometimes the problem fixes itself after a couple of days of me just leaving it and when I press the power button after that period it just magically seems to turn on.

However I have an assessment coming up and all my documents are on this computer so I don't have the luxury of waiting around for it this time. Does anyone know what the problem is and a solution to this?

I should also mention that when I switch the PSU switch off the keyboard lights would flash after a few seconds - but other than that there is no signs of life and I'm not sure what this means anyway

Much appreciated. Thanks
 
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Titan
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What is the PSU brand and model?

If you need to repeatedly RMA your PSU to get your PC to work "reliably" again until the next outage and repeat the process on a regular basis, that sounds like there might be a fundamental design vulnerability with the PSU model you are using and you might want to buy something better/different. If you do not already have a surge protector, you might want to consider something decent like a SurgeArrest Performance or isobar to see if that might help.
 
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aotengs

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Aug 29, 2013
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I've changed PSU models since the problem first occurred. I currently have a Silverstone Strider Plus 600W and before that was an Antec HCG 620W and Antec HCG 520W before that. I do have a surge protector also.
 
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Titan
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A "power outage in half the house" sounds like you may have a problem with electrical service at your location. If there are no issues with the "good" half of the house, there might be a loose connection on the live feed wire for the other half. If your building has 100-200A entrance fuses instead of breakers, one of those fuses might be failing, possibly from old age if it has not been replaced in 15+ years. If lights flicker in the "good" half when the other is out, you may have a floating neutral issue and you need to have that looked at by an electrician since floating/weak neutral can be a safety hazard and can damage/destroy appliances.
 
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aotengs

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We've managed to get an electrician in just now to replace the breakers with ones that can withstand a higher amperage so hopefully if the problem was related to damage caused by overloading it won't come up again. However, I still have the problem of my computer not turning on. Any ideas as to what the problem might be?
 
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Titan
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Did the electrician make sure that existing wiring can actually handle the new breakers' higher rating? If not, this may have introduced increased fire hazard to the list of concerns.

If the cause of breaker trips is floating/weak neutral causing voltage to surge on one half of the house while it sags in the other half, this may have made things worse with loads now experiencing prolonged exposure to abnormal voltage instead of popping breakers.

Did your electrician check for loose feed cable connections, service entrance fuse/breakers and other stuff upstream from the breaker box? If your house got upgraded to a smart meter some time before your problems started, the tech who did the meter swap may have messed up the meter socket in the process (many of them are paid piecewise, which means strong incentive to rush jobs to get more of them done per day, causing many meter panel fires and appliance failures from dirty power) and that could explain some of your issues too.
 
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aotengs

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Aug 29, 2013
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The electrician only replaced the old breaker and that's it. A bit of an update, since the breaker was replaced when I switch on the PSU at the back now the keyboard lights will flash once. Other than that still nothing happens
 
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Titan
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Well, since all three of the PSUs you used are generally considered quite decent, three seemingly identical PSU failures are unlikely so I would start to seriously suspect a damaged motherboard.

Your motherboard probably has a 5VSB indicator LED somewhere on it. When your keyboard's LEDs go out, does that internal LED remain lit normally, dim or turn off? If it changes, it might indicate that something on the motherboard turns on shortly after the PSU gets powered up and shorts out the 5VSB supply, either dragging the 5VSB voltage low (5VSB LED dims) or causing it to shut down. (5VSB LED goes out.)
 
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aotengs

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Aug 29, 2013
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It's an asrock h87m pro4 motherboard and I'm not sure if it has any LEDs on it -I certainly can't see any just by looking at it. This problem has come up many times before and it has worked fine afterwards without a hitch so I'm not sure if the mobo would be the problem
 
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Titan
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That problem should not come up at all, yet it did with three different good quality power supplies.

If changing one variable seems to have no effect on the outcome, it might be time to move on to other variables and the motherboard seems like the logical next suspect to me.

One thing you can try before considering a replacement motherboard would be rebuilding your system outside the case to rule out an intermittent short inside the case.
 
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westom

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Why are you ignoring the many parts of a power system? For example, a power controller orders the PSU on. Then performs many checks. If it does not like what it sees, then a power controller decides to power off its PSU. You would see some LEDs flash.

Your original symptoms (half the house without power) implies your were seeing incandescent bulbs change intensity when other appliances power cycled. The resulting high and low voltages mean many appliances will fail even months later.

Another couple ignored similar symptoms. Fortunately nobody was home when the house exploded. That is a rare example of what can happen months or a year later if you ignore symptoms.

To say more about your system means disconnecting no wires, get a meter, request instructions, and then post numbers so that the fewer who know this stuff can reply. Currently your answers are only as good as the too little facts and no numbers that were posted. Currently only possible is wild speculation.

To get a better answer, state specifically what the electrician really did. And provide numbers as defined by that previous paragraph.

 
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