Asus X99-a II Short-circuit

[petrosssss]

Hi all,

I have an Asus X99-a II board that has been my main computer for a few years now and I would like to continue using it as I cannot afford to move to a newer platform and it still serves me well.

Here's what happened. I had a leak in my house a few weeks ago, and my guess is that a few drops of water fell on the chassis and found their way to the motherboard, either that, or the board just decided to die on me now but the coinsidence is too high to be ignored. I had used it prior to the leak and it worked just fine, then I turned it on last week and the following happens since:

The board will light up for a second or two, code 00, then switch off. Every few seconds it will try to turn on again, same results.

I removed everything, tried with/without memory sticks, CPU, GPU, same result.

I inspected every cm of the board, there is nothing visibly wrong in it.

There is an 8 pin IC that sits between the X99 chipset and the right-hand DIMM slots that gets very warm, almost too warm to touch, its marking is 29 3G U1V(photos included).

I know it's a long shot, but is anyone familiar with this or can guide me on how to solve it?

Thanks!

[piernov]

Re: Asus X99-a II Short-circuit

Richtek RT8065ZQW
https://www.badcaps.net/forum/showpo...84&postcount=2

[petrosssss]

Re: Asus X99-a II Short-circuit

Thanks a lot for your reply, I'm sure this will be useful for many things in the future

I went through all the Richtek PDFs found in that post, but found none with a 29 marking code.

I put 29 in the cross-reference tab at Richtek's site, got nothing, as it needs at least 3 digits. I added a 3(the first digit from the rest of the code on the IC which should be the date and therefore should not be used) and got LM2936 as a result which at least is an 8 pin IC but definitely wrong. I desoldered the IC and it has an exposed pad where GND is, none of the side pins are GND btw.

Any ideas how else I can look it up?

Thanks again.

[piernov]

Re: Asus X99-a II Short-circuit

Google:

"29 YM" "Richtek"

[petrosssss]

Re: Asus X99-a II Short-circuit

Fantastic

May I ask how you figured out the YM bit?

I ordered a few from Aliexpress, in a month I'll know if that was the only issue. Thanks again!

[piernov]

Re: Asus X99-a II Short-circuit

"YM" is the placeholder used in Richtek marking information for datecode "Year Month".

[mgregor]

Did you replace that chip? Did you repair your MoBo? I have the same problem with the same chip and bootloop.

[petrosssss]

Hi,

I did just yesterday, but unfortunately the problem persists, it seems to be some other part of the motherboard(

If you do find a solution let me know!

[mgregor]

Maybe somewhere near that chip there is short circuited capacitor or other component. Did you checked them with mutimeter?

[petrosssss]

There is a possibility that the 2 capacitors in the photo need to be replaced, but I have no way of knowing their value(don't have a capacitance meter, Ohm meter shows they are open). If you can get your hands on a schematic(couldn't find anything) and get their values I'd be happy to replace them and see what happens. The rest of the components are so tiny that I'd never be able to replace.

[harp]

The caps is Cin 10uF and Cout 22uF, but if you measure it open then they are probably good.
When you replaced ic, is it still heating up or not? Have you check for shorts with multimeter while is ic out?
What is voltage on pin 3, 4 and 5 of ic, does it work now?

[petrosssss]

IC is not heating anymore.

Everything was properly cleaned after removing but I didn't check for shorts...

3 goes to 3.4V when powered on
4 is always at 5.1V
5 is at .615V at all times. Can it be that this IC is fried as well? I have another 2 so I will replace it again and this time will check for shorts.

[petrosssss]

The caps is Cin 10uF and Cout 22uF, but if you measure it open then they are probably good.
When you replaced ic, is it still heating up or not? Have you check for shorts with multimeter while is ic out?
What is voltage on pin 3, 4 and 5 of ic, does it work now?

With the new IC I'm getting 1v on pin 5 when turned on.

For a very brief moment the board tried to boot(QCode stayed at 00, memory led turned on). I put a RAM stick and proc, tried again, got again memory led. Then it went back to the on/off cycle. I don't know what else to check, about to give up.

[harp]

Disconect from power and wait few minutes to discharge. On multimeter set resistance mode and measure resistance between ic pin#5 and ground.

If you trace R1 and R2 divider from schematic, you can determine output voltage from included table and see or calculate if 1v is correct output.

[petrosssss]

Disconect from power and wait few minutes to discharge. On multimeter set resistance mode and measure resistance between ic pin#5 and ground.

2.4k

[harp]

Found this topic
https://www.badcaps.net/forum/troubl...nstead-of-1-05

So, check voltage after coil, on pch side, have picture on link. If is nothing suspicious, and if you checked all coil that not have short, and your psu is apsolute ok, I dont know how to proceed next...

[petrosssss]

Coils in the vicinity are not shorted and are at 1.05-1.06V.

Board now stays on but doesn't get past qcode 00, dram led on as well. I've spent too much time on a board and architecture that is getting old. Time to upgrade

Thanks a lot for the help, it's been informative in many ways!