Asus ZenBook 13 UX333F External Short - Fast Battery Drain - Need Help

[jkucukov]

Took literally 5 seconds to get the mosfet removed, my 1st time using the hot air rework station and it was most pleasant experience ever. 380C @ 60L/min with a dab of flux. Didn't have Kapton tape but had plenty of aluminum tape to dissipate heat. Worked like a charm!

[mon2]

Very nice. Now flux and solder coat that region with leaded wire solder and remove access with desolder braid. This coating will make soldering back a fresh mosfet easier due to the low temp solder. For the desolder braid, we use a high temp pencil soldering iron from Weller with a blade tip. Ample heat to make the solder turn to liquid state. The PCB has multiple layers so acts like a heatsink and the braid can get stuck to the board if your soldering iron is not hot enough.

[jkucukov]

With the 2nd mosfet removed, the values of the 1st mosfet (M3056M) from the front side of the MB are as follows:

Source <> drain = 5.88 Mega Ω
Source <> gate = 4.6 Mega Ω
Drain <> gate = 1.34 Mega Ω

Those values look great to me, what do you guys think?

Edit: measuring the removed mosfet shows same low resistance values

[mon2]

Perfect. Replace the defective mosfet.

[jkucukov]

Perfect. Replace the defective mosfet.

Shipping options from Amazon aren't the best:

Ebay tends to have longer lead times as products are all exclusively from china.

You've mentioned Digikey in passing, any other trusted sites?

[jkucukov]

Very nice. Now flux and solder coat that region with leaded wire solder and remove access with desolder braid. This coating will make soldering back a fresh mosfet easier due to the low temp solder. For the desolder braid, we use a high temp pencil soldering iron from Weller with a blade tip. Ample heat to make the solder turn to liquid state. The PCB has multiple layers so acts like a heatsink and the braid can get stuck to the board if your soldering iron is not hot enough.

This is the best I have on hand, some super wick and 3 solder wires:

The no name brand (blue cap RoHS tag): According to the MFG tag its 99.5% Sn and 0.1% Lead

Gray Craftsman Lead Free Rosin Core is Low Melting Aloy 96% Tin and 4% Silver

The roll of Maiyum Rosin Core solder is 63% Sn and 37% Lead

What would you recommend out of the 3 options I have?

[mon2]

Suggest to use 60/40 leaded solder, not lead free solder for rework. Then you will have a lower temp to melt the 60/40 solder.

We buy this stuff in bulk from Amazon:

https://www.amazon.ca/Austor-Activit...s%2C87&sr=8-11


Guessing you will have something similar. Lead free solder will eat away at your solder tips.


Desolder braid is fine.

Let me check the mosfet options and post back. I believe that I linked a few good ones from DK already from Alpha Omega. You do have the metal bottom pads so this is ok for the replacement as well.

[jkucukov]

The Alpha Omega aon3414 was based on a Panasonic mosfet, the mosfet I have is a5 p0903bea from Unikc. I tried searching for an equivalent p0903bea on Digikey with no luck.

[mon2]

Here are some suitable candidates:

https://www.digikey.com/en/products/...ON7528/3603570

https://www.digikey.com/en/products/...ON7418/3061091

https://www.digikey.com/en/products/...ON7428/2353898

[piernov]

The no name brand (blue cap RoHS tag): According to the MFG tag its 99.5% Sn and 0.1% Lead

The roll of Maiyum Rosin Core solder is 63% Sn and 37% Lead

Cheap leaded solder from Aliexpress generally performs worse than lead-free solder. Really suggest sourcing a good spool locally. At the very least check how both flow on another PCB with low iron temperature, but I wouldn't trust that to make good solder joints.

[jkucukov]

Here are some suitable candidates:

https://www.digikey.com/en/products/...ON7528/3603570

https://www.digikey.com/en/products/...ON7418/3061091

https://www.digikey.com/en/products/...ON7428/2353898

Thank you sir, the 1st link is the perfect fit. Didn't think I was getting 10 to make it worth while shipping. Now I need to find some applicable 0805 and 01005 capacitors to go along with the order. Typically are the beige and gray colored MLCC capacitors of a certain capacitance?

[jkucukov]

Cheap leaded solder from Aliexpress generally performs worse than lead-free solder. Really suggest sourcing a good spool locally. At the very least check how both flow on another PCB with low iron temperature, but I wouldn't trust that to make good solder joints.

Found a good one today, non Aliexpress brand.

[jkucukov]

Here are some suitable candidates:

https://www.digikey.com/en/products/...ON7528/3603570

https://www.digikey.com/en/products/...ON7418/3061091

https://www.digikey.com/en/products/...ON7428/2353898

Looking through the datasheet I found a discrepancy on the 1st link with the AON7528 mosfet, the DFN size under the detail description shows as 3x3 while in the Datasheet pdf its shown as 3.3x3.3.

Strangely there seems to be two Datasheets in existence for the AON7528, both carry a version date of May 2012 Rev0. I attached the two I got, one from DigiKey and the other from Octopart. The Datasheet from the Octopart site seems to show the right 3x3 size.

AON7528 (DigiKey).pdf

AON7528 (OCTopart).pdf

[mon2]

The pcb pads will always be larger than the solder legs of the device. The minor dimension difference should not affect the soldering of the replacement parts. However, the use of a 3*3 mm device will be ideal. Also the other devices have the ability for higher current support.

[jkucukov]

The pcb pads will always be larger than the solder legs of the device. The minor dimension difference should not affect the soldering of the replacement parts. However, the use of a 3*3 mm device will be ideal. Also the other devices have the ability for higher current support.

I received Digikey delivery today on the two AON7528 mosfets, at 1st glance the new mosfets were larger than original, but they were still able to fit on the board. I got it soldered in with hot air station no problem, bit crooked.

Assembled the laptop and we have picture, that's crazy!

Battery is charging, orange light is on and everything seems to work.
I'll take it apparat again and show my 1st mosfet install ever, not the cleanest..

[jkucukov]

Here was my makeshift setup for the day