Pc doesnt start (motherboard or switch problem?)

August 9, 2017 at 01:53:42
Specs: Windows 10 pro x64, Core i3 2120 / 2x4gb ddr3
My pc was randomly turning off then on until yesterday when it happened alot and failed to start after that
I opened the case and used screwdrive to turn it on and it worked then i connected the reset button to power pins and it worked
Then i closed the case and tried to turn it on but nothing happened
I then opened the case and tried the screwdriver and strangely it didnt work
Then i removed all power supply cables and reconnected them and the screwdriver worked but the reset button didnt
I want to know what might be the cause of this and iam afraid that i may damage the motherboard by doing these things alot

See More: Pc doesnt start (motherboard or switch problem?)

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August 9, 2017 at 02:21:09
Probably needs a new PSU. Try changing that first and see how you go from there.

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August 9, 2017 at 02:27:37
I dont think its the psu
I bought it last month and beside that i managed somedays to keep the pc on for up to 10 hours running heavy games like mafia 3 and battle field 1
I also did burn in test in furmark which should give a crash if there is a problem in the psu but nothing happened
The random turn on and off wasnt regular it happened some days and some days not until pc failed to start

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August 9, 2017 at 06:01:07
Might pay to check carefully inside the case (with all power removed) to se if there are any short cts. present - as in anything touching the case where it shouldn't be; and also that all connections from the psu are sound...

As you seem to come back to a reset button - possibly that is faulty. They are very simple and cheaply made; and known to fail... If you take an insulated wire with two crocodile clips (one at each end and ideally each insulated) and connect it across the switch terminals and then re-apply power, possibly it will confirm the state of the switch? Ensure that whilst you are connecting the crocodile clips - there is NO power attached...

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August 9, 2017 at 11:07:57
If you think it's the case switch, the test is easy enough. Just remove it and see. You can simulate a button press by touching the two switch pins on the MB with something conductive. I use a screwdriver, myself.

If the crashes keep happening with the switch disconnected, I'd suspect the PSU, and recommend you verify voltages coming from the PSU. Do so by back probing the connectors with a multimeter when the system is on. Pin outs are available with a Google search.

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August 9, 2017 at 11:46:24
It seems my english is bad
There is as strange thing which is that i tocuhed the two switch pins while the case was open and it turned on then i used the reset button instead of power button and it worked
I opened the case after that and tried the screwdriver but the pc didnt turn on and then reapllied all of the psu connections and tried the srewdriver and it did turn on
What does that seem to be? Why the screwdriver turned it on at first then failed and after reapplying the psu cables it worked again? It made me so afraid the mb is damaged
For the psu there is alot of extra cables which i dont know where to put and some of them may tocuh the case from inside. Can that be a reason for anything?
(Iam very sorry for my bad english)

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August 9, 2017 at 13:17:06
"I dont think its the psu
I bought it last month"

Power buttons rarely go bad. As the others have said, it's sounds like a power supply issue. You didn't tell us the make/model or wattage of the PSU you just bought, but I suspect it's not a good one. Post the PSU info & we'll let you know if you made a good choice or not.

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August 9, 2017 at 13:35:56
Have to disagree re'
power buttons failing - especially if they are mechanical type. The simple rocker mechanism can fail at any time. I have known them to go intermittent and/or simply fail. The jumper wire with insulated clips is a simple and safe way to test; either with the switch in place in which situation when power is applied the system will power ok - thus confirming the switch is faulty; and if the system doesn't power up then the psu or connections to the motherboard are faulty. Testing the switch removed from the system and with a meter in ohms setting will likewise show if the switch is ok or not.

If the switch is not mechanical then again it can be faulty, and the jumper wire test as above will confirm its condition.

I know of nearly new mains radios with non mechanical on/off switches which have failed. A lot of press (non mechanical) switches are prone to fail, and do so more than is realised.

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August 9, 2017 at 13:46:13
Power buttons on PCs are momentary switches, like a doorbell button, there's very little mechanics to them. Press to make contact & then release. There's no much that can go wrong with them.

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August 9, 2017 at 14:40:22
Again I have to disagree; and for the reason I gave above re' a main/portable radio series. That radio has such a switch and the model has history of repeated failures with that switch; as do several others (and not just that particular manufacture). Incidentally more than a few dvd units have had similar issues at times. And in broadcast kit the worst thing to to have is momentary on/off button.. - again for the reasons already given; generally they try to avoid such "never fail' items - as invariably they will... and at the wrong moment and in the most unfriendly situations...

I think one may find that some of the on/off problems (actually will not turn on) with some Nikon cameras are similar...

The radio model to which I refer can be "encouraged" to to power on (and then again similarly off) if one presses a few times, or holds the "button", or even in effect wiggles the pressure about as one press it.. All manner of approaches seem to work at times; but nothing conceals the fact that the switch (a momentary press/contact type) hath failed... The cost of the "switch' is peanuts; but to have it replaced if not under warranty is almost as much as a new radio - or whatever piece of kit...

The brand name in question (the stuff is made in China..) has lost a good deal of customer credit and recognition as a result of such poor kit (switches); and the brand name is now no-longer considered as high as once was - when it was a company in its own right (manufactured its own kit) and not simply an acquired brand name for whomever to exploit.

Also I sem to recall that some HP (or was it Lenovo - or both) laptops have had similar problems with their "never fail" on/off buttons...

Tests as above will ascertain if the "never fail" switch is in fact ok - or not...

message edited by trvlr

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August 9, 2017 at 14:53:44
Well, as much as I like a good digression, response #5 says the issue continues when the switch is removed from the setup.

Which just leaves the PSU, the MB, and the CPU. This still sounds like a bad capacitor in the PSU, but you should be able to test it by waiting until it acts up, and while leaving the MB connections in place, use a piece of wire to connect the green wire to a black wire through the back of the MB connector. That should turn the PSU on, regardless of what the MB wants. If the power rails are there, it's probably either the MB/CPU. If you're getting 0 volts, and you're sure the green wire has made contact with a black wire, it's probably the PSU.

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August 9, 2017 at 15:29:38
mmm - re' the switch being removed from the equation - at least what appears to be the case? I wasn't entirely sure that was what was happening... But presuming it is out of the equation completely then yes a psu problem is possible ; and leaky/failed capacitors - even a duff/faulty/dead... rectifier may be the problem?

If we can get the poster to try the jumper routine with the case open and also with the system closed up... we might truly eliminate the switch from the list; which at present I don't think it is?.

The olde use a screwdriver across the switch terminals to short out the switch is OK - as long as one doesn't inadvertently as in - (by accident...) short out the volts across it to wherever. And this may be what's happened?

However... when I read the original post again - more carefully I njote this:

I opened the case and used screwdrive to turn it on and it worked then i connected the reset button to power pins and it worked

Where was the screwdriver applied; and was the reset switch fully removed or disconnected?

Is the reset switch also the actual power on/off switch (usually at the front on most desktops) or is there a separate on/off switch (be it mechanical or simple press briefly type) and also a reset button. And if both where are they located in the system.?

Any details on the make and model of the computer in question?

I am wondering if one of the mains connections is actually intermittent... - presuming they go directly to the reset switch (which is actually the on/off switch too)? With that in mind it may still be the psu as the system was turning off randomly to start with; and that does sound like a psu issue?

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August 9, 2017 at 17:06:21
If the psu is faulty can it handle heavy load when the pc is stressed? Iam pretty sure the random turn off/on wasnt related to pc load
Some days it didnt happened at all some days it did

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August 9, 2017 at 17:06:48
The psu is cooler master watt 500 watt

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August 9, 2017 at 17:10:07
In the front of the case there are 2 buttons one for turning on and the other is for reset or restarting the pc

I tried connecting the wire coming from the reset buttons to the power sw pins on the motherboard and pressee it the pc turned on

But after that the reset button didnt work at all

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August 9, 2017 at 17:12:18
I should also note that the case is pretty old i got it nearly in 2009 and ever then i changed hardware inside but never changed the case
My gpu : msi gaming x gtx 1050 ti

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August 9, 2017 at 19:19:06
I also noticed that when i first used the screwdriver to turn it on it urned on normally without any issue or restarting repeatedly as it did before it failed to turn on

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August 9, 2017 at 22:13:51
Intermittent faults are always hard to find.
Does the system start in cold/cooled-off condition?
No loose CPU fan?
If there is an onboard GPU, does it make any difference without the MSI-GPU present?
Run the system with one memory sick.
Perhaps other (not essential) peripherals disconnected. Try to run with bare minimum.

It can be a time consuming activity to locate the culprit.
The last thing is the motherboard or CPU.

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August 9, 2017 at 22:40:09
I dont understand what you mean by cold or cooled off condition
The gpu doesnt make any difference
When i turned it on by using screwdriver i stressed it doing heavy benchmarks and kept it running for nearly 4 hours and no issues appeared

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August 9, 2017 at 22:42:00
I also checked the pc health status in bios settings the voltages, fans and temp were normal
Every time it did restarting it self i checled the pc health status and all voltages were normal

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August 10, 2017 at 06:10:36
Just to remove my konphusion here as to which switch does what...; or at least (being a little pedantic) clarifying the switch/reset items.

Yours has an on/off switch and a reset switch; which is not uncommon on some desktop systems; generally both are not present as such on laptops - which have in effect a reset button integrated into the on/off button.

The reset requires main in be present - and in effect trigger a cold boot in its effects.

A bit of history...

On modern and ATX and other boards (but not the older AT style boards) unless one kills the power in - by removing the power cord from the mains supply, or by a dedicated power on/off switch (which does in effect remove all mains power into the system) there are volts running around the motherboard. This fact is often overlooked by many the unwary, those not aware of it. It is the reason why when inserting RAM, or making any changes inside a PC using such boards, one does ensure that the mains power is removed completely - first. This has been the situation since 1998 at least.

Your reset switch only works when there are volts incoming from somewhere – and it’s not physical on/off switch.

My recollection is that some of these simple press only (reset in your case) switches are not totally passive; but do actually require a voltage present to function - and it's not mains level. They are usually fairly bulky compared to the simple “passive” version; because they include a wee bit of electronics. Some are a simple passive device - much as riider commented; you press and it makes or mimics a brief closure, and the circuits it its terminals control then lock up and maintain power supplies around the system - until you hit the reset button again... The second press (the first enabling power on) triggers the bi-stable to change state and disconnect power to wherever...

So in your system what that reset button is likely controlling a simple flip-flop chip; which in turn enables power to the motherboard - from the psu outputs. Press the reset once and power goes on to wherever; press it again and the power is disabled/disconnected (but there are still standby volts running around as mentioned earlier). The reset button/switch is nothing more than a simple open/close control path to a chip which is a bi stable/simple flip-flop integrated circuit. That chip can hold either of two states - one is it switches on a control voltage to other items, the other is disables it. It's a bit like a gate keeper (all be it in reveres in the analogy). It opens a gate to allow the volts to flow wherever, or closes the gate and thus stops the volts/current flowing...

With this I mind I suspect that the reset cct. itself is faulty; in that the chip that reset button controls either has totally failed, or at least is intermittent.

Applying mains to the reset button directly many not have been the best option; as I recall they usually require a very low voltage (5 volts dc typically) to operate (and this is derived from the psu output...).

You may be able to locate the chip - trace out the wiring etc.? Equally a circuit diagram for the motherboard may (ought to) show it Whether or or not you can get a replacement and then actually remove the original and fit the new - depends on how the original/current one is installed. If it's soldered directly to the motherboard that is not always a simple procedure to replace. One needs patience, the correct soldering iron - and again patience (and expertise...) If per chance it's a physically sitting off the motherboard then possibly you can replace it?

Why you have the problems as ddescribe4d earlier – depending on case being open/closed etc… ? This being an old case… could be some insulation on some wiring somewhere isn’t all as good as it might be; and thus a conductor itself is momentarily touching the case and triggering the resets etc.

I’d be inclined to carefully – with all power removed – inspect all wiring and check that no=n of its touching the cases etc. anywhere it shouldn’t. Also look for possible wee small objects that may be causing a short ct.s somewhere between the case and the motherboard; and pay special attention to any “standoffs” between the motherboard and the case. They are the insulated (or used to be) mounting points and possibly one of those is playing up…? It may be that the motherboard has shifted slightly on its mountings and thus there is connection intermittently so) between a track on the motherboard and a mounting point?

Even opening and moving bits around, and then closing the case – even repeating that – can cause things to move slightly as and produce the above effects.

So I suspect you have two areas to consider the reset switch itself and/or the power supply feeding it with (presumably) 5 volts. General wiring etc. around the psu and the case in general. And possibly even a third, that being something shorting between the motherboard and case – a foreign body; something small and metallic/conductive; or loose mounting points as mentioned above?

Presumably the system will boot OK initially even if the reset no longer works?

Thee first links may be useful reading; and the Youtube videos more than helpful… if you have to replace the reset button/switch?






And if you simply google for:

reset switches in computer

you'l get all of the above and some images (many) of what they look like etc.. and their associated wiring connections.

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August 10, 2017 at 08:10:52
Is it possible to change the buttons with their wires or the whole case must be changed?

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August 10, 2017 at 09:11:13
Not having done it myself, but based on my researches via google I'd be inclined to say it's relatively simple in many cases; simply remove the present reset button/switch, install a new one and plug it into the motherboard? Wise to check that a possible replacement will fit of course into the hole in the case?

If you repeat my search as suggested at the end of my previous above (and using the same search words) you'll see a host of images showing the nature/style of switches. They all appear to be simply plugin connections to the motherboard? Also the Youtube videos will be a useful study guide?

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August 10, 2017 at 20:51:39
You should be able to purchase any momentary contact button and install it either in the same location in the case or if necessary, in a new hole that you drill that does not get in the way of anything else. You would then connect the old leads to the new button so it plugs into the motherboard.
As mentioned, examine all wires for internal breaks which can cause all kinds of intermittent problems and bare spots in the insulation which can cause shorts. Look for wires caught under components, under screws, too close to fans, pinched under and around the power supply, even under the motherboard.

You have to be a little bit crazy to keep you from going insane.

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