Burnt mosfet on power supply

[debi]

Hi guys,

i do have a problem with a PCB coming from a LG tv. I have a blown 5a fuse on the bottom right corner directly after plugging the power cable. After few test with my multimeter i found a burnt 24N60M2 mosfet... i tested almost all the components on the card unless the PFC/PWM controller IC. I saw somewhere it could be shorted as well.

My electronic skils are limited so im sorry for this stupid question but could someone explain me how to test the PFC/PWM controller IC or any component that could be linked to the dead mosfet ? I found the datasheet of this IC but for me it s like reading chinese (ref 3BR4765JZ) : "Off-Line SMPS Current Mode Controller". (http://www.datasheetcafe.com/3br4765jz-datasheet-smps-controller/)

I ordered the mosfet and id be really happy if replacing it would fix my LG TV but electronic is full of surprises.

Thanks for your help

[PKTKS]

Don't just replace the MOSFET and hope for the best.

Usually the MOSFET shorted BECAUSE something else...

You should replace the MOSFET and PRIOR to turning
things on again checking all caps related to that MOSFET

YOU ARE REQUIRED TO USE A VARIAC WITH DIM BULBS
to prevent another short...  This will save you time and money

SMPS - in particular modern integrated and PFC models are
not  trivial just  replace and go ...

You should also check 2 SMPS typical problems
- LOAD SHORTs
- SOFT START failures.

This model in particular uses a 431 feedback loop which
requires some thinking on the load/start procedure.

NOT trivial .. random things will just be lucky shots. or not

Paul

[aqibi2000]

And check diodes for shorts

[debi]

Thanks guys for your messages

The diodes are ok and caps too

A simple Dim bulb tester without variac could do the job ?

im looking forward building this tester i never heard about it looks really useful.

[wraper]

Usually the MOSFET shorted BECAUSE something else...

Usually MOSFET dies by itself. However often it also damages PWM controller and anything other connected to it's gate in the process.

[PKTKS]

(..)
A simple Dim bulb tester without variac could do the job ?

im looking forward building this tester i never heard about it looks really useful.

Yes. Probably will salvage the MOSFET front end to toast
in the first try. 

Ideally the VARIAC would raise it safely.

The BULB *SHOULD*  do the bottom line trick

Paul