Help me repair this UX305 motherboard please

[Clinteastwood1]

Hi,

I'd like to repair my laptop's motherboard (UX305 i7 cpu). The laptop turned off abruptly when I was working on it and now it won't turn on again.
The charger is working fine (tested) and when I plug it nothing happens, no charging led, the laptop only vibrates slightly when I put my hand on it as usual meaning the current is passing through it. The laptop seems like dead though.

I tried:
- removing the battery and press the start button during one minute to drain out any current from the MB. No start up
- I tested the charger it's fine.
- I tested the charging connector it's fine.

The MB is faulty.

I've seen many videos and almost everytime the 2 mosfets which are near the charging connector and which play a safety role, are often the culprits

So I am planing to replace both. I don't know how to measure them to see if they are working or not (on the videos I've watched, it's not very clear to me) so nevermind I'll replace them straight away and hope I'll get lucky.

My question :
Could you please tell me if these 2 safety mosfets are the ones I circled in blue, or the ones in red? To be sure...
And can someone tell me the type/brand/model to buy as replacement.

Thank you very much for your help.
Best regards

[Stevedb]

Re: Help me repair this motherboard please

You can remove them and measure D-G , S-G , D-S ON resistance mode 200 ohms and the should be all Ol or 1depends on the multimeter. First you must decharge the mosfet with touching your finger to each pin.

Good luck

Best regards

Steve

[Clinteastwood1]

Re: Help me repair this motherboard please

Thank you much for your help Steve.
Do you know a way to test them without removing them please?
I'm rather sure it's one of these 2 mosfets that is faulty, many videos I've watched almost all conclude the same.
Do you know if they are specific to my laptop or these are standard parts? What's their exact name, so I can buy them ? Thanks again

[JJR]

Re: Help me repair this motherboard please

On the two nearest the dc jack you should have 19v in and 19v out.

[Clinteastwood1]

Re: Help me repair this UX305 motherboard please

At any pin?

[Clinteastwood1]

Re: Help me repair this UX305 motherboard please

Here are the best pics I can take with my phone I hope it helps to identify the mosfets

[Techtiger]

Re: Help me repair this UX305 motherboard please

Hi,

I'd like to repair my laptop's motherboard (UX305 i7 cpu). The laptop turned off abruptly when I was working on it and now it won't turn on again.
The charger is working fine (tested) and when I plug it nothing happens, no charging led, the laptop only vibrates slightly when I put my hand on it as usual meaning the current is passing through it. The laptop seems like dead though.

I tried:
- removing the battery and press the start button during one minute to drain out any current from the MB. No start up
- I tested the charger it's fine.
- I tested the charging connector it's fine.

The MB is faulty.

I've seen many videos and almost everytime the 2 mosfets which are near the charging connector and which play a safety role, are often the culprits

So I am planing to replace both. I don't know how to measure them to see if they are working or not (on the videos I've watched, it's not very clear to me) so nevermind I'll replace them straight away and hope I'll get lucky.

My question :
Could you please tell me if these 2 safety mosfets are the ones I circled in blue, or the ones in red? To be sure...
And can someone tell me the type/brand/model to buy as replacement.

Thank you very much for your help.
Best regards

don't remove components unless you are not sure by doing this you will tamper MBD first check +19V is switching the 2Fets are N-Channel MOSFETS check the voltage on both of them S D G if the Voltage on the Gate is less than +20V it will not gate pass this voltage comes from CHARGE MANAGE IC SN2867RUYR pin 4 ACDRV (22-28V) find out PR8906 it's other side of the MBD what is the Voltage ?

[Clinteastwood1]

Re: Help me repair this UX305 motherboard please

Hello techtiger and thank you much for your help.
I'd like to test what you suggest but it sounds like chinese to me
I can't locate where are the gate/drain/source on the mosfets since I'm not electronics savvy... But I'm going to search on Google if I can find a tuto for this.

Concerning SN2867RUYR and PR8906 I am afraid I can't find these. Here are pics of the back of my MB:

[mcplslg123]

Re: Help me repair this UX305 motherboard please

Ok, i try to make it simple for you.
D=Drain-pin5-6-7-8
S=Source=Pin1-2-3
G=Gate-Pin4

Both are N channel fets. So there should be 19V on D and S Pins. The gate should be higher, say 25V approx.

[Sametbey]

Re: Help me repair this UX305 motherboard please

see the measuring points in the picture. These are the ACIN entrance mosfets. their feet should not be short circuited.

https://www.badcaps.net/forum/attach...2&d=1523561177

[Clinteastwood1]

Re: Help me repair this UX305 motherboard please

Thank you very much guys that's very kind to help me.
I took some mosfets measures before I read your messages, with the multimeter in diode position.
If needed I can take more measures according to your instructions.
The measures indicating "1" mean the mosfet is faulty, right?
Thanks for the doc sametbey, I have an ux305ua it's slightly different from this one, but it could help too

[Sametbey]

Re: Help me repair this UX305 motherboard please

As shown in Picture 1, some MOSFETs may show low resistance on the circuit. The picture2 must first provide 19V ACIN sys to the motherboard. then standby 3.3V and 5V come into play.

[Sametbey]

Re: Help me repair this UX305 motherboard please

As I followed from Boardview, 1 and 2 mosfets are ACIN. 2 Mosfet short circuit, should not be 1oHm.

[Clinteastwood1]

Re: Help me repair this UX305 motherboard please

sametbey those schematics are hieroglyphs for me
In fact the ones indicating "1" in diode mode should be in short circuit, because when I use the multimeter in ohmmeter mode it indicates huge resistances for those mosfets (if I understand correctly the "1" in diode mode does not equals to 1 ohm it's a convention to say there is no continuity in the component, meaning huge resistance, at least my multimeter works like that I guess it's a basic one).

[Clinteastwood1]

Re: Help me repair this UX305 motherboard please

Mcplslg123 I made the measures for the mosfets I circled in red in my initial post here is what I get on the first pic below.
Sametbey I made the measures in ohms (caliber 200k) in blue on the second pic. Values at 1 mean infinite resistance.

[Sametbey]

Re: Help me repair this UX305 motherboard please

Stndby voltages, can you check. After that, there may be an IO chip problem.

[Clinteastwood1]

Re: Help me repair this UX305 motherboard please

Stndby voltages, can you check. After that, there may be an IO chip problem.

I get 0V for both when my charger is plugged in

[Techtiger]

Re: Help me repair this UX305 motherboard please

Hello techtiger and thank you much for your help.
I'd like to test what you suggest but it sounds like chinese to me
I can't locate where are the gate/drain/source on the mosfets since I'm not electronics savvy... But I'm going to search on Google if I can find a tuto for this.

Concerning SN2867RUYR and PR8906 I am afraid I can't find these. Here are pics of the back of my MB:

now you have correctly given the voltage measurements with the help of the Mcplslg123 suppose +19V line is ok you can move forward
MBD needs 3/5ALWS Sametbey have request Standby Voltage the 2 Gragy Coils middle of the Bord with 4 Fets take down the Voltage
after in the keybord connector find out the Voltage in pin 5 this is your power BTWN voltage in the keybord it shoud be 3.3V
find out WINBOND W25Q64 IC this your BIOS CHIP (near CPU) voltage on pin 1 and 8 ? and for the last RTC section for this you need the ASUS UX305 Bordview

[Techtiger]

Re: Help me repair this UX305 motherboard please

you need to downlode Bord Viewer software to open this

[Clinteastwood1]

Re: Help me repair this UX305 motherboard please

now you have correctly given the voltage measurements with the help of the Mcplslg123 suppose +19V line is ok you can move forward
MBD needs 3/5ALWS Sametbey have request Standby Voltage the 2 Gragy Coils middle of the Bord with 4 Fets take down the Voltage
after in the keybord connector find out the Voltage in pin 5 this is your power BTWN voltage in the keybord it shoud be 3.3V
find out WINBOND W25Q64 IC this your BIOS CHIP (near CPU) voltage on pin 1 and 8 ? and for the last RTC section for this you need the ASUS UX305 Bordview

Thanks techtiger for coming back helping me.

- Keyboard pin 5 = 3.3v

- WINBOND : pin 1 : 0.11v, pin 8 : 0.28v

- the 2 Gragy Coils middle of the Bord : 0v

you need to downlode Bord Viewer software to open this

Ok will do but I don't have any laptop to open the software (since my laptop is this one and is faulty) I am on my smartphone. Btw I have a ux305UA

Edit : I checked again all the mosfets for continuity (multimeter in ohmmeter mode) and I finally found there is always a pair of pins where I can find continuty in all of them. So I guess they are all good