Lenovo Ideapad S440 Turns on then straight off (Short)

[74kieran]

Hi,

I currently have a Lenovo ideapad S440 which turns on and then straight off. The light flashes red.

I have checked over the motherboard and can here a quiet ticking sound when plugged in. I have tested and noticed that PQ902 is shorted as I have tested pin 2 and 3 to 6 and 7 and I am getting continuity. And if I test the ohms I am getting 0. I have checked the same mosfet which is next to it and that one is correct and showing ohms.

I have attached a image below but I can't seem to find the mosfet replacement I need. All I can work out is "6508". Would this be the version I need? Or is there a specific one I need?

Thanks
(Newish to motherboard repairs)

[mon2]

Re: Lenovo Ideapad S440 Turns on then straight off (Short)

Hi. No it can be replaced. From where do you prefer to purchase your parts ?

Do you deal with Mouser / Digikey / Arrow ? Aliexpress is always a good source but you can sub this other devices.

Datasheet for the original mosfet is attached.

[74kieran]

Re: Lenovo Ideapad S440 Turns on then straight off (Short)

Great Thanks I will take a look. I will look for a UK company just so it isn't a long wait for delivery. Can I just bypass the mosfet for the moment to test it or is it best to not do that?

[mon2]

Re: Lenovo Ideapad S440 Turns on then straight off (Short)

NO NO NO - never bypass the mosfet. It is too risky. Let me check my records - pretty sure that TI has some very good and suitable replacements for the mosfet.

See attached. This is a suitable replacement and is available from Digikey as of this writing. The AON device is EOL but I am sure that Aliexpress will have it in stock.

[74kieran]

Re: Lenovo Ideapad S440 Turns on then straight off (Short)

Amazing! Thanks for your help

[74kieran]

Re: Lenovo Ideapad S440 Turns on then straight off (Short)

Hi,

I have taken the mosfet off and was still shorted. I have now tested the mosfet by the battery and it is measuring the correct voltage. But then there is a fuse ( I think) PF201 with a 12 on which is getting warm. And there is no voltage going through it and there is continuity on it.

Would this be the fuse? Or would a fuse be like this?

Thanks

[74kieran]

Re: Lenovo Ideapad S440 Turns on then straight off (Short)

Here is it PF201

[74kieran]

Re: Lenovo Ideapad S440 Turns on then straight off (Short)

Ignore previous messages

I have been trying to locate a clicking sound on the mobo but so far no good.

[rediii]

Re: Lenovo Ideapad S440 Turns on then straight off (Short)

Ignore previous messages

I have been trying to locate a clicking sound on the mobo but so far no good.

clicking sound? mostly it's cpu/pch or gpu (because of all the transistors cutting down due to power loss or power cycle). it does not mean it's dead though...