[SOLVED] PSU - molex RGB issue

[Thoughtful_Yeti]

Hello i have searched as much as i can online for a answer to this problem, i believe i may need to buy a new PSU but would like some confirmation and advice before i look at this.

So i recently bought a new AIO cooler with two fans on the radiator block, both fans and the pump have RGB in them, the Pump and fans are working fine (and so is the RGB i dont think this is a issue with the cooler) it is a 3 pin RGB connection so this one cant go into my motherboard like my other RGB strips can however the kit came with a switch and molex power adaptor so this is how i am powering it.

So i set it all up and booted and everything was fine the RGB's were working at this point, i then realised that i forgot to put my GPU 8 pin power connector back in so i shut down and connected it and i then found the RGB's for the AIO that were connected to the Molex had stopped working. And after some testing if i remove the GPU power they work again, i have tried different molex connections but these RGBs just dont get power when the GPU is connected, i am assuming that this is some kind of issue with the power going to the molex adaptors, the PSU is a Corsair VS650 (i know its not great but is all i could afford at the time) and i have tried unplugging other things from the PSU like two of my 3 hard drives but it is still the same and only seems to work when the GPU is not connected. Can anyone confirm this is a PSU issue? all the calculators online say i only need 400 watts, and i am not experiencing any other problems but i am aware the PSU is not great and i should upgrade it anyway but want to be sure.

Some specs in case they help:
Mobo - MSI X470 Gaming Pro
CPU - Ryzen 7 2700 (not overclocked atm)
2x 8gb DDR4 Corsair Vengeance RAM 3000
GPU - MSI Rx 570 8GB Armor OC
PSU - Corsair VS 650

 

[anotherdrew]

That is very strange. It's easy to assume that the PSU is at fault and it probably is. Only thing I can think is that the 12 Volt rail is not giving quite 12 Volts (like 11.7 or something).

 

[Thoughtful_Yeti]

That is very strange. It's easy to assume that the PSU is at fault and it probably is. Only thing I can think is that the 12 Volt rail is not giving quite 12 Volts (like 11.7 or something).

Thanks for the reply, i know they are not overly accurate but both the Mobo settings and MSI Dragon Centre show that it is giving 12v, appears normal from what i can tell, the PSU is less than 3 years old so i will speak to Corsair and see what they say

 

[Elisis]

That is very strange. It's easy to assume that the PSU is at fault and it probably is. Only thing I can think is that the 12 Volt rail is not giving quite 12 Volts (like 11.7 or something).

And VS is known quite well for doing this, particularly with modern systems, as can be seen in Aris' review: https://www.techpowerup.com/review/corsair-vs650/2.html
I do doubt that such a voltage drop would cause the issues we're seeing here, however.

 

[anotherdrew]

And VS is known quite well for doing this, particularly with modern systems, as can be seen in Aris' review: https://www.techpowerup.com/review/corsair-vs650/2.html
I do doubt that such a voltage drop would cause the issues we're seeing here, however.

100% agree. Even with a 10% drop in voltage on the 12V rail, I would expect LEDs to light up ... just 10% dimmer. It's like there is no power on that cable and that baffles me.

** I have made an assumption here the fan RGBs run on 12V because that is common. They could be running on 5V. If that was the case you would expect things like SATA drives (if you have any) and USB to be affected.

 

[Thoughtful_Yeti]

100% agree. Even with a 10% drop in voltage on the 12V rail, I would expect LEDs to light up ... just 10% dimmer. It's like there is no power on that cable and that baffles me.

** I have made an assumption here the fan RGBs run on 12V because that is common. They could be running on 5V. If that was the case you would expect things like SATA drives (if you have any) and USB to be affected.

Hey, the RGB's are 5v from what i can tell, my Mobo has the headers for the 12v RGB's so connecting them there would have been fine but as they are 5v they use a 3 pin connection which my Mobo does not have, so i used the molex adaptor that comes with the AIO cooler kit, cant the Molex output both depending on which pins are in use? also if it was related to this how come the RGB's would work when i unplug the GPU?

 

[anotherdrew]

Yes, the 4 pin molex provides 12V and 5V (yellow wire is 12V, red is 5V, black is ground) ... Regular RGB is normally a 4 pin with 12V ... Addressable RGB is 3 pin and uses 5V. Your video card PCIe plug is all 12V and ground. I think that is why I was fixating on the 12V rail.

When you connect your GPU, you are pulling a lot more power from the 12V rail. That is really the only difference from a power perspective ( 100 W ish ... but that's really only when your GPU is working hard, so ... yeah, still does not make sense).

 

[Thoughtful_Yeti]

Yes, the 4 pin molex provides 12V and 5V (yellow wire is 12V, red is 5V, black is ground) ... Regular RGB is normally a 4 pin with 12V ... Addressable RGB is 3 pin and uses 5V. Your video card PCIe plug is all 12V and ground. I think that is why I was fixating on the 12V rail.

When you connect your GPU, you are pulling a lot more power from the 12V rail. That is really the only difference from a power perspective ( 100 W ish ... but that's really only when your GPU is working hard, so ... yeah, still does not make sense).

Thank you for your input though nice to have that confirmation, will see what Corsair comes back with as it should still be in warranty.

 

[jonnyguru]

i then realised that i forgot to put my GPU 8 pin power connector back in so i shut down and connected it and i then found the RGB's for the AIO that were connected to the Molex had stopped working. And after some testing if i remove the GPU power they work again, i have tried different molex connections but these RGBs just dont get power when the GPU is connected,

What are you using to power your GPU? Your VS650's PCIe power connectors or are you using an adapter to adapt a Molex to a PCIe power connector?

 

[jonnyguru]

And VS is known quite well for doing this, particularly with modern systems, as can be seen in Aris' review: https://www.techpowerup.com/review/corsair-vs650/2.html
I do doubt that such a voltage drop would cause the issues we're seeing here, however.

You do realize that spec is +/- 5%, right? The +12V in Aris's review only dropped 2.1% when he OVERLOADED the PSU to over 700W. And the actual drop below nominal +12V was < 1%.

 

[Elisis]

You do realize that spec is +/- 5%, right? The +12V in Aris's review only dropped 2.1% when he OVERLOADED the PSU to over 700W. And the actual drop below nominal +12V was < 1%.

Ah, my mistake. Sorry.

 

[Thoughtful_Yeti]

What are you using to power your GPU? Your VS650's PCIe power connectors or are you using an adapter to adapt a Molex to a PCIe power connector?

Hey, i am using the PCI-e 8 pin connector direct from the PSU, there are two of these both on the same cable, i have tried both but as expected this made no difference, i thought about testing a Molex to PCI-e adaptor but even if this did work i dont see it as a viable solution as there would still be a problem with the unit.

 

[jonnyguru]

Hey, i am using the PCI-e 8 pin connector direct from the PSU, there are two of these both on the same cable, i have tried both but as expected this made no difference, i thought about testing a Molex to PCI-e adaptor but even if this did work i dont see it as a viable solution as there would still be a problem with the unit.

It won't work. I was making sure you were NOT using a Molex adapter because, if the RGB LEDs are using +12V, all of the Molexes are soldered down to the same point inside the PSU and the load from the graphics card could be causing the LEDs to not get enough power.

So I'm still a little confused... did you ever determine if your LEDs use +12V or +5V?

And which VS do you have? The old one (orange "VS" letters) or the new one (black letters on gray background)?

 

[Thoughtful_Yeti]

It won't work. I was making sure you were NOT using a Molex adapter because, if the RGB LEDs are using +12V, all of the Molexes are soldered down to the same point inside the PSU and the load from the graphics card could be causing the LEDs to not get enough power.

So I'm still a little confused... did you ever determine if your LEDs use +12V or +5V?

And which VS do you have? The old one (orange "VS" letters) or the new one (black letters on gray background)?

I did check they are 5v and it is the older VS650 with the orange.

 

[jonnyguru]

I did check they are 5v and it is the older VS650 with the orange.

Ok. So it doesn't make sense that plugging in a +12V graphics card is causing +5V RGB LEDs to not light up.

Unplug everything and replug everything. You have a loose or wrong connection somewhere.