Computer Will Not Power On After Power Outage

My computer has an asus-p8z77-i-deluxe, intel i7-3770k processor, 16gb corsair vengeance ddr3 memory, gtx 1660 super gpu and Silverstone 450 watt psu. All shoe horned into a case about the size of a shoebox.

Today the power went off in our neighborhood for about 2 hours and came back on. I was playing WoW when this happened. When power came back on I tried starting my computer and nothing. The fan didn't start on the psu. I removed it thinking it was bad and jumped pins 16 and 17 and the psu started up and had correct voltages on the wires. I removed the power sw connector and checked it getting infinite ohms when power button is not pressed and 1.7 ohms when it is. Plugged everthing back in and made sure everything was seated correctly and tried starting with the same initial results. Nothing, no lights, fan didn't run on psu, nothing.

Is there a relay on the mobo for turning on psu? What is my next step?

 

Just removed everything but one stick of memory. Again nothing, no lights, no psu fan.

 

Well, not sure how old your specific computer is but considering that motherboard came out in 2012, I'd say 13 years is a good run. And it does sound like the motherboard has finally died. However, since everything inside the case depends on good, clean, stable power, I would swap in a known good power supply to verify you are providing that before spending money (or more time) on anything else.

Shorting the two pins just verifies the PSU can turn on. Not sure what you mean by correct voltages on the wires. The PSU must output +12VDC, +5VDC, and +3.3VDC on various points and those voltages must be within industry standard tolerances of ±5%. That said, to "conclusively" test a power supply, it must be done under a variety of realistic loads. Just measuring from the main power connector does not achieve that. Plus, most meters do not test for ripple or other anomalies. Therefore, proper and conclusive testing is done under load with an OScope or dedicated power supply analyzer.

But of course, most folks don't that sort of test equipment handy so swapping in a known good spare is the next best thing.

No.

 

I tested the voltages, red- 5vdc, yellow- 12vdc, orange- 3.2vdc, blue- (-)12vdc. However I did not measure under a load. The computer was bought in April 2013. It had a good run I admit. Don't want the hassle or expense of getting another computer. I will buy another psu and try it.

 

While I personally think anyone who works on computers professionally, as a hobby, or as the default family/neighborhood go-to computer nerd should have a spare PSU on hand just for such occasions, buying one when you don't know for sure you need one (or what would be a good size to buy) may not be a wise choice. It would be better if you can borrow one from a trusting friend or family member. But if not possible, then I might suggest getting a decent 650W supply (unless you will be doing serious gaming in the future - then 750 - 850W).

Almost as good a swapping in a different supply is using a PSU Tester. While not ideal, I keep a PSU Tester in my tool bag in my truck for house calls. The advantage of this type model is that it has a LCD readout of the voltages. With an actual voltage readout, you have a better chance of detecting a "failing" PSU, or one barely within the allowed tolerances (at least with the tester’s internal load).

HOWEVER, they only have a small (~10Ω) dummy load and they don't measure for ripple. But they are still better than a typical multimeter with no load at all.

 

This psu is a sfx and I hadn't had much need for buying one. I have many hobbies, of which computer repair is not one of them. I do it solely out of necessity. I will spend 50 bucks on a psu and if it doesn't work, I'll have a spare...lol. I just can't figure out why the psu will not even power turn on when power button is pushed.

 

Because it is not really a "power button". That is, it is not directly tied to the PSU. It is a remote button that shorts +5VDC between 2 pins that activates a momentary circuit on the motherboard. That circuit, depending on its current status, then signals the PSU to start.

Note another requirement of the ATX Form Factor standard is that whenever the PSU is plugged into the wall (and, if equipped, its master power switch on the PSU back is set to "On" or "|"), the PSU will supply +5Vsb standby power to various points on the motherboard, including pin #16. It may be that that +5Vsb voltage is missing or the motherboard no longer senses it.