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PSU 12V rails jumps from 12.0 to 12.25V under load - is this fine?

GER_T4IGA
By GER_T4IGA
in Power Supplies
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I read ATX Spec is +-5% voltage wise. My PC has been crashing lately and I wonder if the following could be the issue

Ilde I measure 12V at Molex connector but under MSI Kombustor load that jumps to more than 12,10 volts. Saw 12.25 at some point.

is this fine?

http://linustechtips.com/main/topic/334934-unofficial-ltt-beginners-guide/ (by Minibois) and a few things that will make our community interaction more pleasent:
1. FOLLOW your own topics                                                                                2.Try to QUOTE people so we can read through things easier
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3 minutes ago, GER_T4IGA said:

I read ATX Spec is +-5% voltage wise. My PC has been crashing lately and I wonder if the following could be the issue

Ilde I measure 12V at Molex connector but under MSI Kombustor load that jumps to more than 12,10 volts. Saw 12.25 at some point.

is this fine?

What PSU?  The Molex is otherwise unloaded, right?

 

Could be that the +12V sense is detecting a drop AT A LOAD and is compensating to bring the voltage up to +12V.  But at a connector without a load, it will read higher.

 

That's Ohm's law.

 

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13 minutes ago, jonnyGURU said:

What PSU?  The Molex is otherwise unloaded, right?

 

Could be that the +12V sense is detecting a drop AT A LOAD and is compensating to bring the voltage up to +12V.  But at a connector without a load, it will read higher.

 

That's Ohm's law.

 

Sounds like it
Corsair SF750

I switched from daisy chained GPU power to separate cables now and now the voltage only fluctuates between 11,98 and 12,01

Could daisy cables cause crashing?

 

 

 

http://linustechtips.com/main/topic/334934-unofficial-ltt-beginners-guide/ (by Minibois) and a few things that will make our community interaction more pleasent:
1. FOLLOW your own topics                                                                                2.Try to QUOTE people so we can read through things easier
3.Use PCPARTPICKER.COM - easy and most importantly approved here        4.Mark your topics SOLVED if they are                                Don't change a running system

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No, that's not the cause of your issues.

Quote me to see my reply!

SPECS:

CPU: Ryzen 7 3700X Motherboard: MSI B450-A Pro Max RAM: 32GB I forget GPU: MSI Vega 56 Storage: 256GB NVMe boot, 512GB Samsung 850 Pro, 1TB WD Blue SSD, 1TB WD Blue HDD PSU: Inwin P85 850w Case: Fractal Design Define C Cooling: Stock for CPU, be quiet! case fans, Morpheus Vega w/ be quiet! Pure Wings 2 for GPU Monitor: 3x Thinkvision P24Q on a Steelcase Eyesite triple monitor stand Mouse: Logitech MX Master 3 Keyboard: Focus FK-9000 (heavily modded) Mousepad: Aliexpress cat special Headphones:  Sennheiser HD598SE and Sony Linkbuds

 

🏳️‍🌈

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1 hour ago, GER_T4IGA said:

 

Could daisy cables cause crashing?

 

 

 

Yes.  Again... That's Ohm's law.  😉

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6 hours ago, jonnyGURU said:

Yes.  Again... That's Ohm's law.  😉

So U=R×I

To much resistance in the cable causes the voltage to rise to deliver the necessary power to the GPU? Is that how it works. 

 

Also I forgot to state, that that Molex is loaded with an Aquacomputer Quadro with <5W of Fans and ~10W of LEDs as well as a DDC pump running at very low speed. 

I didn't change the LEDs or the fans from one test to the next. And the power on voltage before the LEDs came on wasn't any different then when the come on so i suspect they have a little to no effect. 

 

 

Also I love this place. I can ask a question about my stupid PSU problems and the real JohnnyGURU will answer my question. 

I read a LOT of your PSU reviews in the past 🙂 but maybe not enough yet 😉

http://linustechtips.com/main/topic/334934-unofficial-ltt-beginners-guide/ (by Minibois) and a few things that will make our community interaction more pleasent:
1. FOLLOW your own topics                                                                                2.Try to QUOTE people so we can read through things easier
3.Use PCPARTPICKER.COM - easy and most importantly approved here        4.Mark your topics SOLVED if they are                                Don't change a running system

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14 hours ago, jonnyGURU said:

But at a connector without a load, it will read higher.

I just realised i was unclear.

This is why I was so puzzled by my measurements: the Voltage doesn't drop, in increases under load of the GPU, although I measured at the Molex.

http://linustechtips.com/main/topic/334934-unofficial-ltt-beginners-guide/ (by Minibois) and a few things that will make our community interaction more pleasent:
1. FOLLOW your own topics                                                                                2.Try to QUOTE people so we can read through things easier
3.Use PCPARTPICKER.COM - easy and most importantly approved here        4.Mark your topics SOLVED if they are                                Don't change a running system

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1 hour ago, GER_T4IGA said:

I just realised i was unclear.

This is why I was so puzzled by my measurements: the Voltage doesn't drop, in increases under load of the GPU, although I measured at the Molex.

Right.  Resistance causes the voltage to drop.  The PSU "sees" that and increases the voltage.  But then you measure the voltage on a wire with no load, so it's higher.  The difference you're seeing is what the PSU is increasing by to compensate for the load.

 

Outside of the PSU, you only have sense wires on the 24-pin, but inside the PSU, there are multiple voltage sensors.

 

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