No Sign Of Power Supply To Pc After Power Failure

Hope this is the right forum.
I was using my desktop and there was a power failure. When I tried to re-start nothing happened, no beeps no lights no fans. I assumed it was the PSU after ruling out the usual things, swapped out cords , power points etc. So I got a new psu and same thing happened. No sign of power, The paper clip test says the psu is receiving power. Could the sudden shut down damaged the motherboard?. Or if not the motherboard what else could it be?
Hoping some one can help. Old dog

 

well.... that would have been my first guess also. it could be lots of things... so i'll relate a story that happened to me.
a computer at work shorted out... smoke and everything coming out the back. with a new power supply installed, still nothing.
my first thought was RAM, since it is more sensitive to power surges. changed out the RAM, still nothing. so i put the original RAM back in. cutting to the chase.... it turned out that the 3 addon cards went bad, video / sound / network. the RAM, CPU, MB, and hard drive were all fine, but all 3 slotted cards burned out. and it was like .... ummmm, oh well... electricity is a funny thing, and it would depend on how the wiring on the MB is laid out.
and one last thought... get a UPS battery backup. they are invaluable and a life saver!
good luck with it.

 

What do you mean by "power failure"? Did the power to your whole house go out? Or did the computer suddenly lose power? Those are two totally different events.

Not likely the shutdown but some event that caused the shutdown - such as a large power surge or spike coming from the mains. Or there could have been a component on the motherboard or old power supply that failed. At this point, there is no real way to know.

By paper clip test, I am assuming you shorted the two pins in the power supply's main 20/24 pin connector and the PSU started, right? That is good but not conclusive because it only shows the +5Vsb standby voltage is present and the PSU is able to start. It does not verify all three main voltages (+12V, +5V and +3.3V) are present where needed, within proper tolerances, and "clean" (without excessive ripple or other anomalies).

If me, I would connect the new PSU to the computer components as they normally would, then follow the two wires from the case's front panel power switch to where they connect to the motherboard's front panel "header" (a set of pins). Note the two pins the two wires connect to. With a steady hand and a small flat tip screwdriver, CAREFULLY and momentarily short those 2 motherboard pins together. The computer should start up.

If it does, you likely have a faulty front panel power switch. If it still does not start, disconnect all drives, remove your RAM, and all USB devices, and speakers. Make sure the necessary power cables are connected to the motherboard (note most motherboards require 2 connectors). If using a graphics card and if it requires an extra power connection (many do) make sure it is securely fastened. Then short the two pins again.

It should try to start but will fail immediately due to no RAM or keyboard. If nothing, your motherboard is likely toast. If it tries to start, insert 1 stick of RAM and connect the keyboard and mouse and short the 2 pins. It should make it through POST (power on self test) and halt when it cannot find a boot disk. If that works, connect the boot drive and see what happens.

Be sure to take the necessary ESD precautions. That is, make sure you unplug the computer from the wall and touch bare metal of the case interior to discharge any static in your body BEFORE reaching in near the motherboard, and before touching or inserting/removing RAM.

While this could be a motherboard component deciding it was time to go, I agree it could have been caused by a power anomaly from the grid (or another faulty device in the house) that caused a component to fail, shutting down the computer. I always recommend that all computers be on a "good" UPS with AVR (automatic voltage regulation). Note it is the AVR that is the main feature of these valuable protective devices. Battery backup power during a full power outage is just a bonus. Surge and spike protectors are little more than fancy and expensive extension cords. Surge and spike protectors also become less and less effective as they age.

 

Thanks for the reply Digerati,
The power outage was a total house blackout during a storm. I went through the steps as suggested with no luck so I thought motherboard. I decided to build another as my computer was getting on in years so I connected the second hard drive through a ide/sata to usb adapter to an old xp computer found in the back room to retrieve my work files (yeah, I know, if I wasn't such an idiot I would have backups allready) . This worked fine so I hooked up the main c drive with the OS on it from the blown computer and no matter how many times I tried it showed up as if there was no disc there. I am wondering if overload that caused the power outage got past the cut out switch on the power board and fried the HDD. Would that stop everything else from working?
Thanks again for the reply, Digerati.

 

An excessive power anomaly certainly can take out anything connected to that power supply. It is not common as power supplies are supposed to cease outputting if a fault is detected. But we are talking close to speed of light speeds here, so even a perfectly running quality power supply cannot fully suppress a determined Mother Nature.