5V Rail low voltage - bad motherboard?

[wele]

Hey guys,

 

System specs as follows:

R5 2600 @4.05Ghz @1.32V~

Asus Prime B450m-a mATX

3200C16 @3200C14 with tight timings @1.4V (CJR)

Vega 56 Sapphire Pulse

RX580 Nitro+ (old GPU, OC@1500/1875Mhz)

Seasonic Focus GX750 Gold (2 days old)

Seasonic Sii12 620W (old PSU)

 

So 2 days ago I bought a Vega 56 and tested it. PC had issues posting and I thought it was my PSU or a bad cable plugged, eventually managed to boot into Windows, play for a bit and went to bed.

Yesterday I got home from work and turned on the PC which failed to boot and post looped for about 5 times until I could boot into Windows. 

Manually rebooted the PC and went into Bios and was greeted with a red 5V voltage (4.3 to 4.4V). Confirmed this reading via HWInfo as well.

I've tried to:

Use my old PSU, same result.

Switch to wall outlet, same result.
Switch to a different wall outlet, same result.

Switch the Vega to a GTX660, same result.

Unplug everything except a monitor, same result.

Unplug drives, same result.

Plug everything outside the case and short the on button on the board, same result.

 

Considering the behaviour persists through PSU changed, I'm inclined to believe the board is the culprit. I'm going to buy an MSI B450 Tomahawk Max unless you recommend something else in this price range (115-130€).
If I confirm the board is the culprit i'll RMA it if not, I'll just straight up RMA the CPU.

Thoughts?
 

 

 

[mariushm]

A video card is powered only with 3.3v (up to 10 watts) and 12v (in theory up to 65w from slot) and 12v from pci-e slots. 

5v should not be affected by video card.

 

My advice would be to buy a digital multimeter, even the crap 2-3$ ones would be fine for some basic tests. It's a very useful tool to have around the house.

 

You can unplug all cables of the power supply (the 24pin, the 8 pin from cpu, the sata/molex to drives, the video card)

You can force the power supply to start by connecting a wire between two pins in the 24 pin connector ... connect a wire between PS_ON (green in picture) and any GROUND pin

Now psu is started, so you can put your multimeter in DC mode (20v or higher if you have to set range manually) and put one probe (black usually) in any ground pin, and the other on the other pins. Put on any yellow pins to measure 12v (should get 11.7..12.3v) , red ones should give you 5v +/-5% , orange ones should measure 3.3v +/- 0.1v

The 5vSB is important (5v standby)... it should be 4.8v..5.3v ... if it's less than that, then that could explain system not starting... 5vSB is used by chipset to initialize motherboard and everything.

 

You can also gradually connect the components... for example connect just motherboard and cpu (24pin and 8 pin).

Leave the video card disconnected.

Connect the multimeter probes to a molex connector (ground and red wires in molex are ground and 5v).

See if the voltage is still less than around 4.8v when you start the pc just with motherboard and cpu connected.

If it's all good, add video card and see again.

It may be that something on the motherboard shorted out and consumes a lot of power from 5v, which forces the power supply to lower the voltage on 5v (because it's not capable of producing so much power on 5v)

It could also be your hard drive or something else that's shorted and preventing power supply from starting though it's less likely.

 

[Vejnemojnen]

@wele Location? You might want to check either MSI B450 Gaming Plus MAX or (if mikroATX is fine) B450m Mortar MAX. (your current mobo is mATX!)

[wele]

13 minutes ago, Vejnemojnen said:

@wele Location? You might want to check either MSI B450 Gaming Plus MAX or (if mikroATX is fine) B450m Mortar MAX. (your current mobo is mATX!)

I'm from Portugal and due to the urgency, I will be buying from a local store:

https://www.globaldata.pt/componentes/motherboards/amd

or

https://www.pcdiga.com/catalogo-pcdiga/componentes/motherboards/motherboards-amd

 

or

https://www.novoatalho.pt/pt-PT/produtos/11211/Motherboards-AMD.html

I have a Zalman Z9 so either mATX or ATX is fine I guess since it supports both form factors. 

[wele]

19 minutes ago, mariushm said:

A video card is powered only with 3.3v (up to 10 watts) and 12v (in theory up to 65w from slot) and 12v from pci-e slots. 

5v should not be affected by video card.

 

My advice would be to buy a digital multimeter, even the crap 2-3$ ones would be fine for some basic tests. It's a very useful tool to have around the house.

 

You can unplug all cables of the power supply (the 24pin, the 8 pin from cpu, the sata/molex to drives, the video card)

You can force the power supply to start by connecting a wire between two pins in the 24 pin connector ... connect a wire between PS_ON (green in picture) and any GROUND pin

Now psu is started, so you can put your multimeter in DC mode (20v or higher if you have to set range manually) and put one probe (black usually) in any ground pin, and the other on the other pins. Put on any yellow pins to measure 12v (should get 11.7..12.3v) , red ones should give you 5v +/-5% , orange ones should measure 3.3v +/- 0.1v

The 5vSB is important (5v standby)... it should be 4.8v..5.3v ... if it's less than that, then that could explain system not starting... 5vSB is used by chipset to initialize motherboard and everything.

 

You can also gradually connect the components... for example connect just motherboard and cpu (24pin and 8 pin).

Leave the video card disconnected.

Connect the multimeter probes to a molex connector (ground and red wires in molex are ground and 5v).

See if the voltage is still less than around 4.8v when you start the pc just with motherboard and cpu connected.

If it's all good, add video card and see again.

It may be that something on the motherboard shorted out and consumes a lot of power from 5v, which forces the power supply to lower the voltage on 5v (because it's not capable of producing so much power on 5v)

It could also be your hard drive or something else that's shorted and preventing power supply from starting though it's less likely.

 

Thanks for the short yet detailed explanation.

Given the fact that I've tested 2 PSUs and the result was the same, would you say the board is the culprit? I cannot test a different CPU which should also affect 5V readings or not?
 

[GoldenLag]

Software reading. Generally inaccurate. As such i wouldnt rrally be worried about it. If it was an issue UVP would kick in. 

[wele]

2 minutes ago, GoldenLag said:

Software reading. Generally inaccurate. As such i wouldnt rrally be worried about it. If it was an issue UVP would kick in. 

Did you even read?

Computer shuts down and fails to boot/post properly due to low 5V voltage.

[GoldenLag]

43 minutes ago, wele said:

Did you even read?

Computer shuts down and fails to boot/post properly due to low 5V voltage.

I did, tho i did miss the part in regards to the bootloop. 

 

My bad. 

[wele]

10 minutes ago, GoldenLag said:

I did, tho i did miss the part in regards to the bootloop. 

 

My bad. 

No problem.
I'm just making sure I'm doing a good accessment of the situation so I want as much feedback as possible.

[wele]

Issue fixed with new board.