ASUS ROG GA502D missing 19v

[jeweemiah]

Hello! No schematics available online for this one sadly.

Laptop not turning on, no charging light

I don't understand why my 19v wont show on the output of the first mosfet.

Should I jump wire only the first mosfet or you guys have any suggestions?

Any help is appreciated!

Laptop

[mon2]

Re: ASUS ROG GA502D missing 19v

No. Never bypass the part till all details are known.

What is the history of the unit ? Are you using the proper adapter for this laptop ?

What are the markings of these 2 mosfets ?

You will need to trace the mosfets to the closest IC which will likely be the charger IC.

Post the markings of the charger IC.

[jeweemiah]

Re: ASUS ROG GA502D missing 19v

Laptop has been dead for a year, decided to try to fix cause why not.

Original charger is being used.

1st mosfet is PKCH2BB, 2nd is M3058M

Charger IC is bq24780s (Is this right?)

Voltage in the picture are the only ones that have values.

How can I possibly find the mosfet for the charging IC?
I also attached a picture of the front of the board maybe its here? the charging IC is literally at the back slightly below of the these mosfets.



If you need anything more measured just let me know

[mon2]

Re: ASUS ROG GA502D missing 19v

See attached for the datasheets for each.

The mosfets can be sourced through Aliexpress (most of the time) or you can find a suitable substitute.

The best starting base is to review the reference schematics from the charger IC vendors which in this case is Texas Instruments (TI). They will note a recommended set of parts and most of the logic board designers will copy the proven reference design.

PKCH2BB
https://www.aliexpress.com/wholesale...psort=1&page=1

M3058M
https://www.aliexpress.com/wholesale...psort=1&page=1

bq24780s
https://www.aliexpress.com/item/1005...rch-mainSearch

Suggestions:

When sourcing the mosfets, review each of the mosfet linked to the charger IC and purchase a few of each mosfet. This includes the first 2 mosfet + high side & low side mosfet + battery mosfet - see the reference schematic inside the posted datasheet. Your logic board will offer similar parts.

While not 100% required at this time, also suggest to source a few of the charging IC from TI from the same vendor. This way you will have all of the replacement parts, if required, with a single shipping charge.

Just ask the same shop if they can supply each of the above parts.

If you do not feel comfortable with Aliexpress - can review to find alternatives. Another tech on this forum noted that you have a local electronics market that may stock such parts. There are many options to replace these mosfets as long as they will fit onto the same SMD pads.

[piernov]

Re: ASUS ROG GA502D missing 19v

https://www.badcaps.net/forum/showthread.php?t=90356

[myth77]

Re: ASUS ROG GA502D missing 19v

Did you check resistence to gnd on that blue parts? and short on mosfets?

[jeweemiah]

Re: ASUS ROG GA502D missing 19v

Did you check resistence to gnd on that blue parts? and short on mosfets?

These are the resistance values measured

1st mosfet =
Source: 51.9 kΩ
Gate: 7.5 MΩ
Drain: 52 kΩ
2nd mosfet =
Source: 51.9 kΩ
Gate: 7.4 MΩ
Drain: 0.001 Ω

Measured 0.001 Ω after the resistor with blue mark.

Both mosfet Source are connected, and all the components that are connected to the First mosfet drain has all the same resistance.

also diode mode on the drain side of second mosfet reads 0.00v.

any thoughts?

[jeweemiah]

Re: ASUS ROG GA502D missing 19v

See attached for the datasheets for each.

The mosfets can be sourced through Aliexpress (most of the time) or you can find a suitable substitute.

The best starting base is to review the reference schematics from the charger IC vendors which in this case is Texas Instruments (TI). They will note a recommended set of parts and most of the logic board designers will copy the proven reference design.

PKCH2BB
https://www.aliexpress.com/wholesale...psort=1&page=1

M3058M
https://www.aliexpress.com/wholesale...psort=1&page=1

bq24780s
https://www.aliexpress.com/item/1005...rch-mainSearch

Suggestions:

When sourcing the mosfets, review each of the mosfet linked to the charger IC and purchase a few of each mosfet. This includes the first 2 mosfet + high side & low side mosfet + battery mosfet - see the reference schematic inside the posted datasheet. Your logic board will offer similar parts.

While not 100% required at this time, also suggest to source a few of the charging IC from TI from the same vendor. This way you will have all of the replacement parts, if required, with a single shipping charge.

Just ask the same shop if they can supply each of the above parts.

If you do not feel comfortable with Aliexpress - can review to find alternatives. Another tech on this forum noted that you have a local electronics market that may stock such parts. There are many options to replace these mosfets as long as they will fit onto the same SMD pads.

Thank you brother for the input I already ordered them online surprisingly all of them would be under 25 bucks, I will be getting five of them each. I will update if they have arrived!.

[myth77]

Re: ASUS ROG GA502D missing 19v

as you can see you have a short on main power rail, short to gnd. Thats why your mosfet is not opening...to prevent damage to motherboard.
The problem is that main power rail is a huge rail...powering everything on the motherboad so it is very difficult to find where is the short.
On gaming laptops it is usually the power mosfets on gpu or cpu line...but it could be a capacitor also.
Double check the resistence in milohms on main power rail? is it exactly 0,001 ohm?
also, make a visual inspection on the whole motherboard to see anything burned maybe or cracked.

[mcplslg123]

Re: ASUS ROG GA502D missing 19v

As @myth77 has correctly pointed out, your +19V rail is shorted to GND. You can inject 1V on CLR just after dc-in fets and observe if anything gets hot. Dont inject more then 1V though you can increase amp gradually.

[jeweemiah]

Re: ASUS ROG GA502D missing 19v

as you can see you have a short on main power rail, short to gnd. Thats why your mosfet is not opening...to prevent damage to motherboard.
The problem is that main power rail is a huge rail...powering everything on the motherboad so it is very difficult to find where is the short.
On gaming laptops it is usually the power mosfets on gpu or cpu line...but it could be a capacitor also.
Double check the resistence in milohms on main power rail? is it exactly 0,001 ohm?
also, make a visual inspection on the whole motherboard to see anything burned maybe or cracked.

My bad its actually 0,1 Ω. I can't see any obvious discoloration from passive components to ICs. Tested some sus caps but they are not shorted at all.

[jeweemiah]

Re: ASUS ROG GA502D missing 19v

I have also tested resistance to ground on some coils and found out that these two coils are both under 1Ω.. Can I narrow down that the short is somewhere here or near?

[myth77]

Re: ASUS ROG GA502D missing 19v

My bad its actually 0,1 Ω. I can't see any obvious discoloration from passive components to ICs. Tested some sus caps but they are not shorted at all.

If it is exactly 0,1 ohm thats pure short to gnd...lets hope its capacitor...if its mosfet then with that low resistence it probably shorted cpu or gpu also.
If you have a power supply do what mcplslg123 advised: inject 1V on CLR just after dc-in fets and observe if anything gets hot with your fingers/hand or use isopropyl alcohol. Dont inject more then 1V though you can increase amp gradually.

[jeweemiah]

Re: ASUS ROG GA502D missing 19v

I sadly don't have a power supply . Is there any other options of finding a short? I don't wanna buy a power supply that I will use only one time.

I asked a laptop and phone repair shop around town and they said don't accept those kind of requests especially disassembled ones, they suspected that it came from another repair shop. I also specifically said that I will take full accountability to the laptop even if nothing happens lol and they still refused

[myth77]

Re: ASUS ROG GA502D missing 19v

unfortunately there is no other way. Even if we found boardview for this motherboard it would be like a huge puzzle...you would had to remove/desolder joints and coils and resistors...to narrow things to a possible short area. But because this line is huge...it would take hours and hours of finding and desoldering parts then again soldering... Its near to impossible.

[jeweemiah]

Re: ASUS ROG GA502D missing 19v

Imma go and ask a friend of my mine if they have something, meanwhile I will still be updating on some and unusual values and info about the issue or If I can find something online.

[jeweemiah]

Re: ASUS ROG GA502D missing 19v

Yo guys, am back so firstly I replaced a shorted mosfet and my CLR on the main power rail after the second mosfet is only reading 4.2v

Any thoughts on my next step after?

[mon2]

Re: ASUS ROG GA502D missing 19v

Remove all power. Meter in resistance mode (lowest scale).

Check the resistance to ground of the 2nd mosfet / main power rail. Post the resistance reading.

Also check if the 2nd mosfet is possibly defective - using resistance checks:

source (1-2-3) & drain (5-6-7-8)
source (1-2-3) & gate (4)
gate (4) & drain (5-6-7-8)

Checking for a low resistance across the above pins. If found, the mosfet is defective and needs to be replaced.

Post the resistance readings.

[jeweemiah]

Re: ASUS ROG GA502D missing 19v

All resistances on lowest scale are OL, reading only starts appearing at 200k scale. all values are 100k +.

[mon2]

Re: ASUS ROG GA502D missing 19v

This mosfet appears to be ok.

Do you see 19v at the first mosfet?

What is the voltage after the mosfet?

Post the voltage readings on the source(1-2-3), gate (4), drain (5-6-7-8) pins of each of the first 2 mosfets.

Then, very very carefully, measure and post the voltage readings of each pin on the charger IC.