[SOLVED] power supply of laptop is broken (220vac-20vdc)

[erchiu]

hello everyone.
this morning the power supply of my laptop has stopped to operate.



until to yesterday evening it has operated correctly, while today it is not lit.
i opened the housing of this power supply, but i have not seen nothing burned.
i checked all resistors and capacitors on the board and these are ok.
in to input of the circuit there is an integrated circuit pwm controller FAN 7554 and one FQPF 12N60C (mosfet)
i checked the voltage on the capacitor in to the input and is live .
there are 320 volts.
what other i can check?
can be the fan7554 broken?

thank you so much everyone

 

[kam1787]

after the resistors and capacitors
try testing for obvious faults
the transformers
diodes
and solid-state devices

if it was dropped
check for any broken traces
or if any leads have broken free

 

[jiripolivka]

In many switching power supplies there are fuses similar to a resistor, and varistors (mostly blue) to limit inrush current.
Most of such molded power supplies are not repairable- no schematics or spare parts available. Buy a new one is my advice.

 

[D.A.(Tony)Stewart]

Any unusual V on FAN7554?

 

[Audioguru]

Did you measure inside the power supply to see if its output cable is broken?

 

[erchiu]

Thank you everyone.
I have checked again all resistors and i found one of these broken.
From the datasheet of the fan7554 and i seen that this resistor supply this IC on pin number 7 directly from rectifier bridge
Always on manual of IC, i see that it is from 330k, but on my power supply it is from 200k, and i replaced it with one from 220k. After this replace the power supply have started to operate.
Thank you so much everyone