Asus X550LD Fan spining non stop

[lapfix]

Re: Asus X550LD Fan spining non stop

RN7521, pin #1 = VGA_SMB1_CLK. = 0.056v

[mon2]

Re: Asus X550LD Fan spining non stop

What is the voltage on RN7521, pin # 2?

Next, remove all power -> measure the resistance between RN7521 - pins # 1 & # 2.

While the power is removed, check the resistance to GROUND of pin # 1 (RN7521).

[lapfix]

Re: Asus X550LD Fan spining non stop

Always with Q7502 removed , RN7521 pin2,3and 4 = 3v

resistance to GROUND of pin # 1 (RN7521). = 37ohm...with another board more than 50.00K ohm...a graphic chip issue !!

[mon2]

Re: Asus X550LD Fan spining non stop

Remove RN7521 and confirm that PCB pad # 1 of RN7521 is indeed 37 ohms still.

Then - Yup. Appears to be that it is U7001 that is pulling down the SCL line and causing the fan to spin non-stop.

If you are left with no choice, you can try a reflow of this device but wait on others to comment but now we know the root cause. Perhaps corrosion related.

If you place back the IO side mosfet, the SCL line should still be a normal 3v.

[lapfix]

Re: Asus X550LD Fan spining non stop

RN7521 Removed = OL
may be i will try a small reflow at the area ob i2cs-scl of U7001

[mon2]

Re: Asus X550LD Fan spining non stop

RN7521 Removed = OL

Really? Double check and if correct, then the fault is with RN7521.

Apply lots of flux and apply RN7521 back onto the board.

Does the resistance become super low after RN7521 is on the board ?

Review the traces and pads nearby RN7521 - do not see a reason why the pin will be a low resistance to ground since none of the pins on RN7521 are mated to a local ground.

In this case, DO NOT worry about the GPU IC - just review RN7521 for now.

[lapfix]

Re: Asus X550LD Fan spining non stop

Hello my friend
Try another RN7521 without Q7502 = resistance pin 1 = 19K ohm..try it i got my 3v at pin 1 and RN2802 pin 1 too.

add another Q7502 and power on , got 3v too , fan spin and my 3v dissappear again...power off ...pin 1 RN7521 = 97 ohm

power again no 3v ..remove Q7502 same and notice : RN2802 pin 1 = 3v...fan spin non stop but without noise