PC won't restart after power outage

Question

Hello,

My entire PC is plugged into a power strip with a centralized switch. I recently cut the power using this switch. Since then, my PC won't restart.

This issue happened to me a year ago (back then I didn't make the connection with the power cut).
After many searches, I managed to solve it by completely disassembling it, removing all connections from the motherboard, and reconnecting the minimum to my motherboard outside the case (CPU power, power supply, fan).

I just tried to do the same thing again, but it still won't restart.

Does anyone have any idea if there is some sort of fuse or circuit breaker on the power supply, or if there is a specific element to check before I dive into difficult tests (motherboard testing, RAM testing, CPU testing, power supply testing)?

The last time I did all these tests separately and there were no issues, and everything returned to normal without any particular explanation (I concluded that one element must have been shorting out against the case).

Thank you for your valuable help.

Manu · Accepted Answer

There are certain power supplies that have a ridiculous safety feature that kicks in during a power outage.
In this case, to restart it, you just need to reconnect the power supply (well, in your case, turn it on with the switch on your outlet) and then cut the power for a few seconds with the switch on the back of the power supply and then turn it back on.

le druide · Answer

Hi,

once the PC is plugged into the power outlet, try holding the power button down for a moment and then release it to see if it starts.

Otherwise, it's a power supply issue; try unplugging most of the equipment, but if you've already done that, it's a big problem!
--
The druid without the potion.

meikyo · Answer

Seriously, I'm a bit freaked out, so your help would be welcome with real solutions.

meikyo · Answer

Thank you Manu for your response which seemed judicious, but unfortunately I tried and it didn't change anything...

Iron Man · Answer

Hello,

To start, test your power supply as shown here http://www.teaser.fr/~abrea/cncnet/trucs.phtml,
if it works, try the following trick:
Remove the processor, the graphics card, and all other cards, and then turn on your machine. If nothing happens, also check the contact points between the power supply and the motherboard; otherwise (like in programming) (if it works) gradually reinsert the cards, turning on each time you add a card and finally the processor.
Also remember to unplug the CD, DVD, burner drives, etc.
A little clarification regarding computer power supplies:

A computer power supply is a switching power supply, to understand the operating principle search for what's in bold on Google and educate yourself. When one of the output pins is overloaded, the entire power supply goes into safety mode, hence the method I propose (it's not unique but incorporates many others).

See you later!

Iron Man · Answer

Remove the overload causing it.

In reality, your power supply sees your motherboard and everything connected to it as a single "resistor" (so to speak, it’s better to say load); each output section of your power supply can only provide a certain power. Beyond that power, that section protects itself, and since it’s part of the power supply, it cuts off all its output voltages, everything in the central unit shuts down except for the power supply fan (personal experience with a motherboard I call trash board, meaning it can fail, I’m not suffering).

To check that it’s your power supply going into safety mode, reconnect it to the central unit and disconnect your CD drive, then test the voltage between the red wire and the black wire and between the yellow wire and the black wire with a multimeter set to voltmeter mode (every computer technician should have one, whether they are a maintainer or not). You should find +5v and +12v respectively if you respect the polarities. If these voltages vary too much, for example, if +5v drops to 2 or 1 v or 0v, it means your power supply is going into safety mode.

As you can see, the overload could come from one of the peripherals, such as the drive or hard disk, or even the motherboard, in which case a motherboard replacement is necessary (if it’s the motherboard). I have indeed sometimes repaired motherboards since 2003 that still work without issues today, but it’s better to change it if you’re not an electronics technician like me.

@+

meikyo · Answer

Thank you Ironman, I want to try to test all this, but I remind you that I am currently testing with only the processor and its fan plugged in.

What surprises me the most is that all this started because I only unplugged the power cord. It's still weird... and I don't understand the logic behind it.

meikyo · Answer

Well, I'm starting to feel desperate... I still haven't found a solution to my problem, and yet I feel like my motherboard isn't fried.

After unplugging and replugging it (I think I've played with the switch several times...), and doing everything you told me, I managed to get it to restart: the power supply turns on and the CPU fan lights up.

So I cut the power once again, and here we go again, it's impossible to restart it.

Conclusion: every time we cut the power, something happens, and it's impossible to know what the manipulation is to get everything restarted.

Thank you PLEASE for your help, as I am convinced that nothing is fried. For your information, I have an MSI 865PE Neo2-P motherboard.

le druide · Answer

To return to your problem that starts to unfold, have you tried booting with the minimum hardware connected to the motherboard, for example: without the CD drive, burner, hard drive, sound card, modem, and all external peripherals connected to the tower as well as all the devices plugged into the power strip if that’s the case.
--
the druid without the potion.

meikyo · Answer

I perform all my tests using only the CPU, the CPU fan, and one stick of RAM.

le druide · Answer

and you only have one stick? -- the druid without the potion.

meikyo · Answer

yes, I only have one... but even without that, it doesn’t change anything, it should at least try to start.

What's weird is that earlier it started again, but as soon as I turn off the power, I can't restart it, and I don't know how I got it to start earlier.

It's frustrating....

meikyo · Answer

both: either by unplugging the power supply from the outlet or by using the button at the back.  Do you have any idea?

le druide · Answer

Does the power come back on when you plug in the cord or when you press the button at the back + the Power button at the front? -- the druid without the potion.

meikyo · Answer

the problem is that the power supply never restarts ... I can only start it by short-circuiting the green wire and the black wire. But if I connect it to the motherboard, nothing starts.

le druide · Answer

Well here it is!  The power button, the one that turns on the PC, does the wire go to the power supply or to the motherboard? -- The druid without the potion.

meikyo · Answer

Thank you for your answers, my friend The Druid, but I'm not sure I understood the last one ...

Here's how I'm testing:

I tested my power supply separately (green and black wire in short circuit) => OK
Then I have the CPU, one RAM stick, and CPU fan on the motherboard
Then I connected the power supply to the motherboard

And there I tried a bunch of things:

- connecting the case power connector to the motherboard (PowerSwitch) => NO GO
- touching the two PowerSwitch pins on the motherboard with a screwdriver => NO GO

And all that while playing with the switch on the power supply located at the back, unplugging and replugging, etc ...

And once it did start, so I'm sure my motherboard is not dead, but something must be causing the power supply to go into safety mode

PS: when I say NO GO, I mean nothing happens, the PC power supply, the CPU power supply do not turn on

Thanks again if you can find a solution for me because I'm losing hope

le druide · Answer

It's very clear here!

I give a 8/10 on the power supply.

In order to proceed by elimination, if you are not using a power strip with or without an on/off button to power your equipment, I would test your tower directly on another outlet to make sure there are no issues with the electrical installation. Also check with another power supply cord for the tower. If nothing works after that, your power supply has issues either with the component soldering or a capacitor that has weaknesses. Finally, get another power supply and that way you'll know for sure.

The druid without the potion.

meikyo · Answer

I've already tried all that without success... I went to a friend's house and tested with his cable, his power supply, and his outlet... to no avail!

By the way, it's at his place that I somehow managed to restart everything, but as soon as I turned off the power, I couldn't get it to restart again.

There has to be a solution and an explanation because I'm convinced that nothing is burned out.

clementfo · Answer

Hear ye, hear ye, same problem, but despite the number of solutions available in your responses, none work :( I'm despairing.

Specifications just in case:
Intel Core i5 6500 processor.
NVIDIA GeForce GTX 1070.
Kingston DIMM DDR4 2x8gb.
MSI B150M BAZOOKA PLUS motherboard
Kingston HyperX Fury SSD - 240 Go.
Seagate Desktop HDD - 1000 Go.
Seasonic M12II Evo power supply - 520 Watts.
5 fans are connected.

PC won't restart after power outage

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