Question PC won't start or POST no matter what.

[Unwo]

Hi everyone,
I'm posting here since im kind of desperate at this point and I don't understand what is happening.

Basically a week ago my pc suddenly died. There is no light on the mobo, it does no sound, the fans do not start, and if I try to attach some USB to the ports always active for charging they don't work. PSU Fans also do not start. Turns out my PSU is fine, and I even tried to start up the PC with another brand new one PSU, with the same results.

Then I had to be away from home for some days. When I came back home I unplugged everything, every cable and component, and built from scratch again. It magically worked perfectly. That was yesterday. I even used it for some hours with no problem at all.

Today I came back from work and PC doesn't turn on, showing exactly the same symptoms from a week ago. I tried unplugging everything and building from scratch again but with no results.

At this point I dont understand what it could be since I guess hardware failure is out of the question. If some hardware was faulty PC should not have started yesterday at all.
I really don't know what to do anymore or what to try. And some researches online got me no results.

Anyone has some tips? Happened to someone else here?

Parts List

MOBO: MSI MAG Z390 Tomahawk - Bought new in 2019, never had problems with it.

CPU: i5-9600k 3.7GHz - Bought new in 2019. Had some problems and got a new one with warranty in 2020.

CPU Cooler: Corsair Hydro H110i - Bought new in 2019, never had problems with it.

GPU: Gigabyte Nvidia 2070 - Bought new in 2019, never had problems with it.

RAM: Corsair Vengeance LPX 3000MHz 16GB (2x8gb) - Bought new in 2019, never had problems with it.

PSU: Corsair RM850x 80 Plus Gold 850 Watt - Bought new in 2019, never had problems with it. (Tried even a new PSU, PC problems still persist.

Case: Antec P110 Luce

Storage: WD Black SSD NVMe 500gb (Used for OS, one game and some programs, about half full)
Seagate Barracuda 1tb SATA (Used for photos/videos/music, about 600 free gb)
Crucial BX500 1tb SATA (Used for games, about 700 free gb).

 

[Ralston18]

Update your post to include full system hardware specs and OS information.

Include PSU(s): make, model, wattage, age, condition (original to build, new, refurbished, used)?

Disk drive(s): make, model, capacity, how full?

Someone may identify a particular component as problematic with similar symptoms.

Try installing a new CMOS battery as a matter of elimination.

However, my thought is that there is a loose or broken connection that arbitarily connects (PC boots) or does not connect (PC fails to boot). Connection being determined by temperature, vibrations, or gremlins of some sort or another.

Plug or port most likely but there could be break in some cable.

Take a very close look at all of them using a bright flashlight and even a magnifying glass. Daisy chained connectors and cables tend to be flimsy.

Include all connections from motherboard to the case front panel.

Look for cracks, bare conductor showing, melting, loose or missing screws. Be sure to pay attention to the area around the I/O port inside and out. Also check around all of the motherboard standoffs. Could be a short somewhere.

Take your time. Examine with the power off and PSU unplugged so you can freely wiggle connections and components.

 

[Unwo]

Update your post to include full system hardware specs and OS information.

Include PSU(s): make, model, wattage, age, condition (original to build, new, refurbished, used)?

Disk drive(s): make, model, capacity, how full?

Someone may identify a particular component as problematic with similar symptoms.

Try installing a new CMOS battery as a matter of elimination.

However, my thought is that there is a loose or broken connection that arbitarily connects (PC boots) or does not connect (PC fails to boot). Connection being determined by temperature, vibrations, or gremlins of some sort or another.

Plug or port most likely but there could be break in some cable.

Take a very close look at all of them using a bright flashlight and even a magnifying glass. Daisy chained connectors and cables tend to be flimsy.

Include all connections from motherboard to the case front panel.

Look for cracks, bare conductor showing, melting, loose or missing screws. Be sure to pay attention to the area around the I/O port inside and out. Also check around all of the motherboard standoffs. Could be a short somewhere.

Take your time. Examine with the power off and PSU unplugged so you can freely wiggle connections and components.

My bad forgot part list. Edited now.
I checked all connection while rebuilding an none is faulty.

I was thinking about CMOS too, but I read online that when CMOS is faulty usually at least leds on motherboard light up when booting the PC.
Could CMOS still cause my type of issue?

 

[Ralston18]

Going back and re-reading:

"There is no light on the mobo, it does no sound, the fans do not start, and if I try to attach some USB to the ports always active for charging they don't work. PSU Fans also do not start"

Is it certain that wall outlet or any other interim devices (surge protector, power bar, extension cords, etc.) serving the computer are working correctly? No electrical system problems.....

As for CMOS - FYI:

https://www.technewstoday.com/motherboard-cmos-battery-dead/

https://techmindy.com/what-happens-when-cmos-battery-dies/

The described symptoms are not a clear match for a battery problem. However, swapping in a new battery is straight-forward and inexpensive.

My thoughts are leaning towards an electrical problem in the wall outlet or even the electrical circuit serving the computer.

Are there problems with other devices using/sharing the outlet and sockets? Or on the same circuit as a whole?

 

[Unwo]

Going back and re-reading:

"There is no light on the mobo, it does no sound, the fans do not start, and if I try to attach some USB to the ports always active for charging they don't work. PSU Fans also do not start"

Is it certain that wall outlet or any other interim devices (surge protector, power bar, extension cords, etc.) serving the computer are working correctly? No electrical system problems.....

As for CMOS - FYI:

https://www.technewstoday.com/motherboard-cmos-battery-dead/

https://techmindy.com/what-happens-when-cmos-battery-dies/

The described symptoms are not a clear match for a battery problem. However, swapping in a new battery is straight-forward and inexpensive.

My thoughts are leaning towards an electrical problem in the wall outlet or even the electrical circuit serving the computer.

Are there problems with other devices using/sharing the outlet and sockets? Or on the same circuit as a whole?

There are no problems with other devices using the power strip connected to the outlet (I have a surge protector in which I plugged my PC, one monitor, a lamp, and a router). I would also add that I am in this house since 6 months and never had problems using the same outlet with the same surge protector.
But can it have a problem only with the PC since it has a bigger wattage requirements?

What do you mean with "electrical circuit serving the computer" ? Sorry, english is not my main language so sometimes I miss some terms.

 

[DaleH]

The PS_ON signal on the 24pin ATX connector is what turns the power on. One needs a voltmeter to check it. It should go from 5V to 0Vdc when the power button is pushed. This will tell you if power is getting to the motherboard.

 

[Ralston18]

"Electrical circuit" first.

(Note: And your English is fine. )

Most electrical systems are divided into "circuits". Each circuit serving different areas within a given home or residence. Some circuits are simply lights and outlets. Other circuits provide power to appliances that on their own demand significant power. Refrigerators, ovens, air conditioners for example.

Circuits use "breakers" (switches) and fuses to guard against too much power going through a circuit. When that happens the resulting heat can cause melting, sparks, smoke, and fire. Circuit breakers trip (open up a switch) when unsafe conditions exist to stop the current flow. Fuses "melt" breaking the circuit to again stop current flow.

Hopefully before a fire can start.

Your residence probably has some central panel containing breakers or fuses. Depends on local electrical codes (rules) and standards. Often ignored and/or not enforced in some places.

"Surge Protector", second.

Does the surge protector have its' own On/Off button? The button could be the problem.

Does the surge protector have a reset button? The reset button is a small breaker and it may be malfunctioning in some manner. Plus surge protectors are rated in Joules with respect to how much energy they can absorb before failure. The value is cumulative and a surge protector can lose its' protective value by one large power hit or a series of small hits adding up.

Even without a breaker the surge protector could be the problem.

Could well be that there is a problem within the surge protector outlet serving the PC. A loose wire there.

Try another known working surge protector and find other ways to provide power to the computer that do not include the existing wall outlet, the surge protector etc..

You may be able to discover the culprit just by some methodical swapping and testing.

 

[Unwo]

"Electrical circuit" first.

(Note: And your English is fine. )

Most electrical systems are divided into "circuits". Each circuit serving different areas within a given home or residence. Some circuits are simply lights and outlets. Other circuits provide power to appliances that on their own demand significant power. Refrigerators, ovens, air conditioners for example.

Circuits use "breakers" (switches) and fuses to guard against too much power going through a circuit. When that happens the resulting heat can cause melting, sparks, smoke, and fire. Circuit breakers trip (open up a switch) when unsafe conditions exist to stop the current flow. Fuses "melt" breaking the circuit to again stop current flow.

Hopefully before a fire can start.

Your residence probably has some central panel containing breakers or fuses. Depends on local electrical codes (rules) and standards. Often ignored and/or not enforced in some places.

"Surge Protector", second.

Does the surge protector have its' own On/Off button? The button could be the problem.

Does the surge protector have a reset button? The reset button is a small breaker and it may be malfunctioning in some manner. Plus surge protectors are rated in Joules with respect to how much energy they can absorb before failure. The value is cumulative and a surge protector can lose its' protective value by one large power hit or a series of small hits adding up.

Even without a breaker the surge protector could be the problem.

Could well be that there is a problem within the surge protector outlet serving the PC. A loose wire there.

Try another known working surge protector and find other ways to provide power to the computer that do not include the existing wall outlet, the surge protector etc..

You may be able to discover the culprit just by some methodical swapping and testing.

First of all thanks for all the info you're providing, you are a godsend.

Yes, the surge protector has its own on\off button. Idk if it has a reset button, I will check once I will go home (at work atm). I will try another surge protector and check if mine has a reset button. Other than that I will try plugging the PSU directly in another outlet (not the one I have the surge protector in).

So could it be that the surge protector or the outlet causes problem only to the PC since it requires higher wattage, while causing zero problems to others devices such as monitors etc. ?

This would potentially rule out MOBO fault, I guess?

 

[Ralston18]

I would like to say that the motherboard could be ruled out.

And there is the fact that the problem first occurred and appeared resolved after you redid the cables.

Then the problem reappeared again.

The initial recovery may have facilitated another more damaging surge - through no fault of yours.

Not necessarily a matter of wattage. The killer is the current and many components will fail when too much current passes through the component. "Too much" simply meaning current (amps) beyond what the component is designed to use and tolerate.

Unfortunately, electrical problems are notorious for zapping or frying components while other components are unaffected. Lightning strikes, for example, can take out all wired devices no matter what wires are being used - audio, network, telephone. The current finds a path to ground (earth) and any component along that path may suffer accordingly. Some components more than others. The others may go with a second strike.

I have seen lighting arc through a room over a bed where I was laying. The spark came in via telephone jack and exited via a wall electrical outlet. Telephone jack was burned a bit. No damage to outlet.

Quite possibly the surge protector may be ok (or partially ok) but some electrical surge got through just enough to damage the motherboard. Motherboard worked until another surge took out what protection remained in the surge protector and finished off the motherboard.

The surge may have taken some roundabout path. Electrical outlet to monitor to video cable to motherboard/GPU etc..

Very much comes down to finding ways to test each component individually and discovering which components work and which do not work.

Hazard being that a bad component may in turn, cause damage some known good component in the process.

Most likely you have changed flashlight batteries only to have the light bulb then blow....

 

[Karadjgne]

Follow the dots. But, must know which dots to follow. A psu that is getting power, and the switch in the rear is set | is On. Always. It's never off. It will always supply power to the mobo, usb etc. That's called standby mode. Off mode is physically disconnected from the wall or the switch in back is 0 not |.

When you push the button, you effectively ground the power-on lead, that sends main power to the mobo. But in standby mode, there's generally at least 1 led on the mobo that's lit up.

So if you push the button and nothing, even with a verified good psu, it's got nothing to do with cmos failure, there's a breakdown prior to the 24pin connection.

Check your wall outlets, remove any extra connections like cheap surge protectors, may even require electrical intervention if other outlets on the chain are the issue.

 

[Unwo]

So, I've tested starting the PC on every outlet of the house and it presents the same problem. PSU with paperclip test has energy with every outlet I tested.
Idk what to do anymore, sadly I dont have spare PC/Components to test them individually.

 

[Ralston18]

Energy is one thing: providing the appropriate energy via the appropriate connections (plugs, sockets, pins) is another thing. PSUs supply three different voltages (3, 5, 12) to various system components. So sometimes the PSU can appear to be working but is actually not fully functional.

Do you know anyone who has a multi-meter and knows how to safely use it?

PSUs can be tested to some extent. Not a full test because the PSU is not underload. However, any voltage(s) out of tolerance would make the PSU a likely culprit.

And all other cables, cords etc. can be tested for continuity while disconnected. Twist, wiggle, gently pull, and so forth to determine if continuity is lost or regained.

FYI:

https://www.lifewire.com/how-to-manually-test-a-power-supply-with-a-multimeter-2626158

Check both PSUs. The old and the new. Plus the cables.

Be thorough and methodical.