[SOLVED] RGB 5pin mystery with select STRIX GPUs

Hardware GPU
1

Need some help here as there is no documentation online of this.

On the STRIX 1080 11Gbps I have, the fan shroud RGB leds use a 5 pin pinout to drive the LEDs, they’re labeled like this:

TOP

  • +GB
  • +R
  • R
  • G
  • B

BOTTOM

But there is no documentation on the side that goes into the PCB.

The wire managed to break off during maintenance and I do not want to solder it back on incorrectly so that it blows up the LEDs.

GPUs that also use this weird 5 pin layout include the STRIX RX 580, and STRIX GTX 1070 Ti. All RTX STRIX GPUs use 4 pins for the RGB on the fan shroud.

How do you measure with a multimeter which one is which? There’s no pre-existing data on what you should expect so without that info, people repairing old STRIX GPUs with this shroud could very well blow up their LEDs.

2

I would set it to (255,0,0) then run a voltage check for all, grounding out to the case. Repeat for (0,255,0) and (0,0,255)

I’m not an EE though, so someone else might have a better recommendation.

I’m assuming you’ve got a common ground in there and one lead for R, G, B, W. With that said, you’ll probably need to voltage test against (255,255,255) as well.

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3

Not possible to control the RGB where I’m going that has soldering equipment. More likely what will happen is it will be left in a default state of breathing.

4

I’d pick up a multimeter from your local hardware store. They’re not super expensive and really helpful to have on hand. If you can do this in your PC, at your workstation, that’s the best solution

Oh, in regards to what you should expect, I’d expect either 3.3V or 5V when a line is on. It’s probably pulse width modulation.

5

The place that has the soldering equipment should have a multimeter, but with no baseline info, it’s going into it completely blind anyways.

Here’s the board for the 4 pin variant:

Aura%20sync%20hack%202
Aura sync hack 2.jpg1062×1683 498 KB

Unlike the 5 pin, the 4 pin is clearly a 12V RGB header.

6

That’s why I’m recommending you test it at home so you can go in knowing what’s up.

7

Here’s the board for the 5 pin variant:

IMG_20191127_154022
IMG_20191127_154022.jpg2592×1944 961 KB

The 4 pin variant uses what looks like shunts on the 12V line to drive the LEDs, the 5 pin variant is completely bare with no shunts.

8

Here’s the best theory I have to go on right now:

Green and Blue are 5V, Red is 12V.

This means the 4 pin PCB is converting the 12V down to 5V for the Green and Blue LEDs.

The R, G, and B, pins are standard RGB PWM.

Using a HDMI output as a 5V rail, only blue and green lit up.

9

Confirmed. With 12V the Red LED lights up.

So this is the best guess:

  • +GB (5V) (GPU PCB Pin 5)
  • +R (12V) (GPU PCB Pin 4)
  • R (Red PWM) (GPU PCB Pin 3)
  • G (Green PWM) (GPU PCB Pin 2)
  • B (Blue PWM) (GPU PCB Pin 1)

For pin numbering, it’s with the notch side up, going left to right.

Also, it seems the +GB is a victim of a PCB trace lining directly up with the vertical part of the plus, wearing out the vertical line in the + making it look like -.

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10

To anyone encountering this thread replacing their 5-pin LED shroud with a 4 pin one, do not fret. Get a 5 pin connector and only populate pins 1-4 going left to right, notch side up. The shroud will work exactly as intended because the shunts on the PCB for the 4 pin variant convert the 12V to 5V for you, so there is no need for a 5V rail.

Same goes if you want to use your card’s fan shroud RGB header if you lack a dedicated 4 pin 12V RGB one. Use a +12V from your PSU, then use pins 1-3 of your 5 pin to control the RGB PWM of your 12V RGB strip. This is how you get a STRIX 1080, STRIX RX 580 and STRIX 1070 TI to have RGB without the dedicated RGB header.

So to wire it up:

12V from PSU ------------> * 12V+

* Pin 1 (B)  --\  /------> * Green (GPU PCB Pin 2)
                \/
* Pin 2 (G)  ---/\/------> * Red   (GPU PCB Pin 3)
                 /\
* Pin 3 (R)  ---/  \-----> * Blue  (GPU PCB Pin 1)

* Pin 4 (12V+)

* Pin 5 (5V+)

Hopefully this gives you the right info to get 12V RGB strips to use the RGB from your STRIX GPU without the dedicated RGB header.

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