Question PC won't power on

[Vybz]

Not sure this is the right place for this question.

My PC is alittle dated and is now not even powering on. After running through quite a few troubleshooting steps I narrowed down the issue to the 4x4 pin power cable for the CPU. If I unplug it the system powers on but once plugged in it does not come on. It comes on with everything else plugged in.

I have tried to take out the CPU clean it and reinstall it with new thermal paste, but that has not worked. What else can I try? Is the issue the CPU? here's the build:

CPU: Intel Core i5-8400
Motherboard: ASRock Z87 Extreme3
Ram: Team DDR3 1600 16GB
SSD/HDD: Crucal M500 240GB, WD Blue 1TB
GPU: MSI GAMING GeForce GTX 1060 6GB GDRR5
PSU: Seasonic FOCUS Plus Series SSR-650FX 650W 80+ Gold
Chassis: Corsair Obsidian 550D
OS: Windows
Monitor: dual dell monitors

 

[Tech Junky]

Well, the 4-pin lead is or OC'ing for additional power. The lead might just need to be replaced. If it's not the lead then it could be the jack it plugs into and that would mean a new MOBO but, you won't lose any performance by not using it.

 

[WilliamM2]

Well, the 4-pin lead is or OC'ing for additional power. The lead might just need to be replaced. If it's not the lead then it could be the jack it plugs into and that would mean a new MOBO but, you won't lose any performance by not using it.

The 4 pin is not for overclocking, it powers the CPU and IS required. In my experience, with the cable unplugged the system will power on, but it won't initialize and boot.

OP wasn't clear on what he meant by "powers on".

 

[Tech Junky]

Might be a different case with older PSU / MOBO / CPU since more recent ATX setups have a 8-pin + 4-pin. CPU only needs the 8-pin to run not the 4-pin since it's just additional power if needed for boost / turbo / OC.

ATX (and PCI-E) Power Supply Connector Guide

sparks.gogo.co.nz

 

[C1]

A scenario that fits what is happening is that the PSU thinks it is seeing a "short" when the 4-pin connector is plugged in, so, for protection, the PSU does not energize.

In an attempt to test such theory, first check to ensure that your MB doesnt have an EZ_PLUG option. If so, try that, otherwise purchase a suitable molex to 4-pin adapter then try that combination.

 

[Vybz]

Well, the 4-pin lead is or OC'ing for additional power. The lead might just need to be replaced. If it's not the lead then it could be the jack it plugs into and that would mean a new MOBO but, you won't lose any performance by not using it.

Its not a 4 pin. its 8 but you use a 4x4 plug. see the plug in the picture and its labeled CPU

The 4 pin is not for overclocking, it powers the CPU and IS required. In my experience, with the cable unplugged the system will power on, but it won't initialize and boot.

OP wasn't clear on what he meant by "powers on".

yes it is required and what I mean by power on is that the PC does not turn on at all. so its does not start post becuase it just does not power on unless in plug out that cable. and since its the CPU cable nothing happens.

Might be a different case with older PSU / MOBO / CPU since more recent ATX setups have a 8-pin + 4-pin. CPU only needs the 8-pin to run not the 4-pin since it's just additional power if needed for boost / turbo / OC.

View attachment 61176

ATX (and PCI-E) Power Supply Connector Guide

sparks.gogo.co.nz

see above for the mobo and the plug I mean.

A scenario that fits what is happening is that the PSU thinks it is seeing a "short" when the 4-pin connector is plugged in, so, for protection, the PSU does not energize.

In an attempt to test such theory, first check to ensure that your MB doesnt have an EZ_PLUG option. If so, try that, otherwise purchase a suitable molex to 4-pin adapter then try that combination.

what do you mean where would I plug that molex to 4 pin?

 

[Tech Junky]

Sounds like the easiest is to get another 4+4 or 8-pin lead to replace the one that's not working. Should be relatively simple or just get an entire new PSU if you plan on upgrading in the near term.

https://www.ebay.com/itm/274315242222 - $5

 

[C1]

Presumably you are dealing with the 4+4 pin connector (ie, the 8 - pin 12v CPU ATX PSU supply connector) and not, as you stated, some other 4x4 pin connector (ie, 16 pins).

Look at this thread - hopefully should help:

[SOLVED] - Does it matter which 4 of the 4+4 pin connector I use to power the CPU power 2?

I have Gigabyte P850GM power supply and the motherboard is MSI X570 Tomohawk WiFi. The power supply comes with 2x(4+4 pins). Each its own cord. The motherboard requires an 8 pin connector and a 4 pin connector to power the CPU. I've connected the 8 pin connector. And I'm confused about the 4...

forums.tomshardware.com

 

[lakedude]

you use a 4x4 plug.

I'm sure Vybz means 4+4...

 

[Vybz]

I'm sure Vybz means 4+4...

Yes that's what I meant. that's why I am so confused here. I tried different cables already because I have more than one. so its not the cable. Am I correct in thinking that only the Mobo and CPU could be the problem?

 

[lakedude]

Am I correct in thinking that only the Mobo and CPU could be the problem?

CPUs very rarely go bad. Last bad CPU I can remember was a Cyrix. Maybe an AMD when a heatsink fell off during shipping back before they put thermal sensors in their chips. I mean it could be a bad CPU but that is just so rare.

The PS and MB are the likely suspects. This whole 4+4 plug thing is especially suspicious. Are your PS cables labeled? Don't use the similar looking cable for the video card! Or the +4 from the main 20+4 pin!!

I mean are you 100% sure the cabling is correct?