Laptop PSU not having primary voltage .

[SM-Piyes90]

Hi again everyone .


I have in hands a 90W 19Vdc 4.5A PSU that got shorted main cables, using power factor correction via transformer and L6561 IC .

So to make the story short i have opened the case , recovered the burned cables , and powered it , and i see no voltage at the Filter cap , so i checked the primary side and i found a small SOT23 ( WB (2A perpendicularly))
semiconductor that is not working , and i just can't find the exact datasheet for it .

PWM IC is ON NCP1203
Current/voltage controller is : M101AC


Here are some pictures :

[SM-Piyes90]

Re: Laptop PSU not having primary voltage .

I have just tried my luck with a bc547 as a replacement , reattached a detached self leg and it worked , but there is still a noise around the self ( the one between red caps)

[tom66]

Re: Laptop PSU not having primary voltage .

What is the mains voltage in your part of Morocco? 230V? You should have primary cap voltage even if PFC isn't working, about 1.4 x AC voltage so with 230V mains it will be around 320V DC and 115V gives 160V DC. If you are not getting this check the fuse, bridge rectifier, NTC thermistor (in-rush limiting), solder joints, and plug are OK.

[SM-Piyes90]

Re: Laptop PSU not having primary voltage .

What is the mains voltage in your part of Morocco? 230V? You should have primary cap voltage even if PFC isn't working, about 1.4 x AC voltage so with 230V mains it will be around 320V DC and 115V gives 160V DC. If you are not getting this check the fuse, bridge rectifier, NTC thermistor (in-rush limiting), solder joints, and plug are OK.

Yes the mains are 230 VAC

I guess the detached self leg was causing the mains voltage to not reach the filter cap ; Or maybe the transistor that i have replaced ? i wonder what was that transistor driving ?