Laptop Ac adapter faulty ...

Thread Starter

battery.13v

Joined Dec 20, 2015
13
hey everyone i have a problem with this laptop ac power adapter, its original problem was that when there is too much load on it it will cycle on and off ... like from 19V to 10V to 19V to 10V every 1 second
so i open it up and i did not found anything visually .. i tested the main capacitor (100uf) and it measured 60uf so i changed it ... and while testing i accidentally made a short between the resistors that are attached between the main capacitor and the ground
after that it stopped working .. after some test i found that the mosfet was dead and i changed also the pwm ic and still not working ... after that i found this two shorted transistors that i dont know what is their role so if someone could explain to me what are they doing and how could i replace them cause they dont have any indications ...thx everyone
i attached a visual explanation ...
 

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Dodgydave

Joined Jun 22, 2012
11,284
Your circuit looks like it has two Npns driving a Mosfet.. You have marked pin 8 wrong, it's pin 5,,,

Better photo of the pcb side would be good..
 

Thread Starter

battery.13v

Joined Dec 20, 2015
13
Your circuit looks like it has two Npns driving a Mosfet.. You have marked pin 8 wrong, it's pin 5,,,

Better photo of the pcb side would be good..
ya sorry for that mistake ... will try to take another one ... and i will try to change them by normal npn transistors maybe ot will work
 
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