Hello brunoaduarte,
You need to remove the white glue from the solder side of the PCB so you
can see what's underneath it all.
Also, you need to check for cracks on the PCB tracks, especially around
the chopper transformer and switching MOSFET. The one connected to the
heatsink.
If you have a magnifying glass or an inspection lamp, use that to look for
any cracks, as there may even be micro-fractures.
Check very closely at the SMD components for fractures also. You can do
rough checks on your multimeter to ensure none of them are broken.
Check your 19V output lead for any wire breaks within it. A low ohms
continuity check would be best. (This is an unlikely problem, but would be
good to check regardless).
Please let us know how you get on... Good luck!!!
Regards,
Relayer
EDIT: It seems I didn't check the solder side of your
PCB close enough. Have a look at your revised picture, and you should see a
cracked solder joint. This may be the real culprit.
View attachment 141796
P.S. I have to say it, but it just shows how poorly the Chinese make devices
for themselves or contracts for other companies. How good is the toroidal
coil wound? It looks like a 5 year old wound it. :???: