lenovo y50-70 VIN mosfets gets hot & possible short

[swammyw]

looking help on lenovo y50-70 mboard: la-b111p zivy2

laptop had shorted capacitor on B+ battery rail and was dead, CHG_B+ PC305

i replaced cap with same healthy cap and laptop started working, i noticed
input mosfest got hot when i start laptop, but when battery is connected vin mosfets get insanely hot but laptop charges and works with battery

-i can hear small spark sound when charger is connected
something draws lots of current but i cant figure out what component it is
-BATT+ mosfet PQ303 gets also pretty hot but when i charge battery it gets insanely hot and it is next to cap i changed
-PU301 battery charge ic is not getting hot
-also pch gets warm / sometimes hot
-PL302 CHG measuring 88 kohm to ground

[mon2]

Re: lenovo y50-70 VIN mosfets gets hot & possible short

Laptop should not be used as a micro furnace.

Remove all power.

Meter in resistance mode.

Check the resistance for each mosfet as follows:

Source and drain
Source and gate
Gate and drain

Post the values.

Checking for low resistance = shorted mosfet.

[ktmmotocross]

Re: lenovo y50-70 VIN mosfets gets hot & possible short

replace mosfet. its burned and have higher resistance. your vin voltage should be lower because of it

[mcplslg123]

Re: lenovo y50-70 VIN mosfets gets hot & possible short

replace mosfet. its burned and have higher resistance. your vin voltage should be lower because of it

Maybe but may not be also. Lets wait for the measurements. Heating up could be for other reasons as well.

[swammyw]

Re: lenovo y50-70 VIN mosfets gets hot & possible short

mosfets get insanely hot even laptop is off and i charge battery only


battery charge mosfets

PQ303

BATT+, B+ = 3.5Ω (short?)
BATT+, DISCHG_G = 187Ω
B+, DISCHG_G = 187Ω

PQ310

CHG_B+, gate =1200Ω
CHG_B+, LX_CHG =53.5Ω
gate, LX_CHG =1185Ω

PQ312

LX_CHG, DL_CHG = 1584Ω
LX_CHG, GND = 226Ω
GND, DL_CHG =431Ω


PQ501

1.35V_B+, SW_1.35V = 1.73kΩ
1.35V_B+, DH_1.35V = 1.75kΩ
DH_1.35V, SW_1.35V = 5.3Ω (short?)

PQ502

SW_1.35V, GND = 247Ω
SW_1.35V, DL_1.35V = 890Ω
DL_1.35V, GND = 110Ω

input vin mosfets

PQ301

VIN, P2 = 70kΩ
VIN, P2-1 = 71kΩ
P2-1, P2 = 150Ω

PQ302

P3, P2 = 1.8Ω (short?)
P3, P2-1 = 152Ω
P2-1, P2 = 152Ω

[mcplslg123]

Re: lenovo y50-70 VIN mosfets gets hot & possible short

Take PQ301/302/303 out of circuit and measure resistance between

Pin1 to pin4
Pin4 to pin5
pin1 to pin5

Repeat the same on pcb after removing the mosfets and draw your own conclusion.

[swammyw]

Re: lenovo y50-70 VIN mosfets gets hot & possible short

can i change ao4455 to ao4433, some values are diffrent a little

[mcplslg123]

Re: lenovo y50-70 VIN mosfets gets hot & possible short

No, there is huge difference in pulsed drain current. 4433 Will instantly burn out.

[swammyw]

Re: lenovo y50-70 VIN mosfets gets hot & possible short

ok thanks