Lenovo G5000 no power missing 3.3v always and 5v always

[mnciks11]

Hello guys

I have a Lenovo G5000 with no power, not charger the laptop, no lights …

I do have the 19v all over the board but I'm missing 3.3v and 5v always, the two power rails are generated by different IC's , 3.3v and 5v…I checked for a short to ground, resistance and more but they seem to be okay, what may causes this board to have to 3.3v and 5v if they are generated by different chips

Both IC's do receive the 19v but both not generating any volts , is there an enable chip separate that should turn on both 3.3 and 5v…

Please I need a clarification on this brothers

[mon2]

Re: Lenovo G5000 no power missing 3.3v always and 5v always

The LDO rails are enabled by pin #3 on each ic.

Post the voltage reading for pin #3 on each regulator.

Better if you post the voltage reading of both chips and if every pin. Meter in DC mode.

Do so carefully as the pin contacts are small. You can, for now, measure the outside parts that eventually will connect to the IC.

[mnciks11]

Re: Lenovo G5000 no power missing 3.3v always and 5v always

3.3v and 5v regulator IC’s pinout

Pin 1 = 0v
Pin 2 = 0v
Pin 3 = 0v
Pin 4 = 0v
Pin 5 = 0v
Pin 6 = 0v
Pin 7 = 0v
Pin 8 = 19.5v
Pin 9 = Ground


One of the above pins has 5v on both IC‘s but enable pin has 0v on both IC’s
Pin

[mon2]

Re: Lenovo G5000 no power missing 3.3v always and 5v always

Voltage on resistor, PR402 pin #1 ?

Voltage on resistor, PR402 pin #2 ?

[mon2]

Re: Lenovo G5000 no power missing 3.3v always and 5v always

Voltage on resistor, PR402 pin #1 ?

Voltage on resistor, PR402 pin #2 ?

This is the 499k resistor shown in the top right of your schematic. This resistor acts like a voltage divider.

Pin #1 should be +B = 19v0 (same as the +B) to the regulator IC.

Then pin #2 of the resistor must be a lower voltage if all is well but you have measured 0V for the enable pin. This is incorrect for a proper turn on enable voltage. Something is wrong in this region of the logic board.