330S-15IKB Components to replace along with shorted power MOSFET

[Shuasmith14]

Hello. I'm currently working on a Lenovo Ideapad 330S-15IKB that has no power, no power light, dead. I found the schematics and I'm seeing proper voltage at the drain of the first DC IN MOSFET and nothing after. After doing some research and finding the power supply troubleshooting guide in this forum. I tested the second DC IN MOSFET and it's shorted from drain to source. My main question is since I'm new to doing this, I thought I heard somewhere that any time a MOSFET goes, you're supposed to replace the controller as well. That may not be right but I want to check if there's anything else I would need to replace with it. I don't want to just replace the MOSFET only for it to blow again. I can upload the schematics I'm using if I need to, or if there's other info you need let me know.

[Sametbey]

Re: Components to replace along with shorted power MOSFET

We also encounter different models. When the second mosfet is short-circuited, it is enough to change it.

[Th3_uN1Qu3]

Re: Components to replace along with shorted power MOSFET

^^ +1 on that. Most designs 2012 or later use very high value resistors on the gates of the mosfets in the DC-in circuit so unless there is liquid damage, the charging IC will be fine 95% of the time and replacing the shorted mosfet is the only repair required.

[Shuasmith14]

Re: Components to replace along with shorted power MOSFET

^^ +1 on that. Most designs 2012 or later use very high value resistors on the gates of the mosfets in the DC-in circuit so unless there is liquid damage, the charging IC will be fine 95% of the time and replacing the shorted mosfet is the only repair required.

Ok, great. I see from the schematic I'm using the gate and source have a 4.02k ohm resistor on each of the pins to the charging IC. So basically if there weren't resistors between the MOSFETS and the IC then that would need replaced too?

[Th3_uN1Qu3]

Re: Components to replace along with shorted power MOSFET

When the mosfet goes completely short, it usually takes out the gate driver as well if IT is coupled directly or via a low value resistor (less than 50 ohms). Most dc/dc converters use no or very low gate resistors because they need to switch the mosfets very fast. The DC-in circuit only needs the mosfets as on/off switches, therefore it doesn't particularly care how fast they act, hence the use of large value resistors on the gates.

[Shuasmith14]

Re: Components to replace along with shorted power MOSFET

When the mosfet goes completely short, it usually takes out the gate driver as well if IT is coupled directly or via a low value resistor (less than 50 ohms). Most dc/dc converters use no or very low gate resistors because they need to switch the mosfets very fast. The DC-in circuit only needs the mosfets as on/off switches, therefore it doesn't particularly care how fast they act, hence the use of large value resistors on the gates.

Ok, that makes sense. Appreciate the in-depth response.

[TheAnswer305]

Re: Components to replace along with shorted power MOSFET

When the mosfet goes completely short, it usually takes out the gate driver as well if IT is coupled directly or via a low value resistor (less than 50 ohms). Most dc/dc converters use no or very low gate resistors because they need to switch the mosfets very fast. The DC-in circuit only needs the mosfets as on/off switches, therefore it doesn't particularly care how fast they act, hence the use of large value resistors on the gates.

Great explanation! Thanks