FX505DD REV 2 blowing MOSFETS

[Proserot]

Hi all,

first of all: Sorry, im kinda new to board repairs. Ive managed to do some repairs before, yet I consider them quite easy (obviously).

A friend of mine had his tuf FX505 spilled with coke. It wasnt used anymore anyway so he gave it to me.

Ive cleaned the board, removed 2 MOSFETS at the CPU PSUs causing shorts all over the board. After I couldnt identify any more shorts, I felt confident in plugging the charger and see how far the juice comes. For a second i couldve sworn I saw smoke...

Then i saw the MOSFET at the Battery connector PSUs fail (5v and 3.3v PSU?). It now has a burned in hole.

What else should and could I check besides shorts? IIRC, measuring resistors while soldered onto the board wont help me a lot.

What could have caused this MOSFET to blow?

Thanks for any input!

(If somebody has the boardview for FX505DD REV. 2.0, I'd be very happy about it! The 505GE etc differs alot)

[Techtiger]

Re: FX505DD REV 2 blowing MOSFETS

If you didn’t replace 2 or 4 ( CPU section) Fets and plug the charger set dead , never do this in CPU section

[Proserot]

Re: FX505DD REV 2 blowing MOSFETS

Im aware of this not being a very good Idea but do you mind elaborating?

The power shouldnt come very far when turned off as only the 3.3 power rail should be powered, isnt it?

[myth77]

Re: FX505DD REV 2 blowing MOSFETS

On asus laptop boards when you remove bios battery and connnect charger it will try to start automaticly.

[Proserot]

Re: FX505DD REV 2 blowing MOSFETS

Oh. Thanks for this information!
I cant help but think thats a stupid design but robably has its reasons. Just gotta know about it. Even tho I couldnt measure any voltage besides 20,5 and 3.3 on the coils