Lenovo Z570 directfet culprit

[lezsimply]

Hello everyone. Just want to ask if its possible to replace a directfet with an ordinary one? Can't seem to find locally on my area. This is for Lenovo Z570 with board code LZ57. Laptop is shorted on dcbatout which led me to this directFet PU4313 on vcc_core. When removed, short is gone. I will attach schematic and image.Thanks everyone.

[Sephir0th]

Re: Lenovo Z570 directfet culprit

Maybe It's possible, but it is Always the Better way to replace Mosfets in switching Power supplies with equal ones and additionally replace Always both (High- and LowSide) of them at the Same time.

This is a High-Side mosfet of VCORE and It's never good, If this one fails. Are your Sure you have No more short on Source-, Drain- or Gate-Pins onboard?

Greetings

[mcplslg123]

Re: Lenovo Z570 directfet culprit

This is a common issue in LZ57 mb. You need to replace both HIGH & LOW side fet plus the pwm for core. I dont know about any alternatives but they are available online. Some russian sites advocate replacing the 4 mosfets at one go for all the phases along with pwm.

[lezsimply]

Re: Lenovo Z570 directfet culprit

Thanks for the reply. In source to drain I get 0.079 vice versa in diode mode. On gate pin I get 0.995. I found short on PL4301 0.004 same diode mode.

[Sephir0th]

Re: Lenovo Z570 directfet culprit

Readings from PL4301 to ground in Ohms Please

I Hope, i'm Not right with my guess...

[lezsimply]

Re: Lenovo Z570 directfet culprit

Good day. I got a reading of 6.4 ohms with respect to ground

[Sephir0th]

Re: Lenovo Z570 directfet culprit

This should be acceptable for +VCC_CORE and means, this is NOT a short. So do as advised from mcplslg123.

[lezsimply]

Re: Lenovo Z570 directfet culprit

I also found out that PTC4303, PTC4306 and PTC4307 is shorted to ground. These 3 tantalums measures 7.2, 7.4 and 8.8 ohms outside board. now PL4301 measures 22.60k ohms.

I'm a little worried because I still have 111.8ohms on pu4313 drain side which could still indicate a short on dcbatout. Thanks again.

[mcplslg123]

Re: Lenovo Z570 directfet culprit

Have you removed the core pwm?? Its also likely to be bad.

[lezsimply]

Re: Lenovo Z570 directfet culprit

I apologize for not updating as I have been busy.

@mcplslg123 yes I removed all 3 pwms still short is still there.

Heres what I did for the past few weeks:

I removed all 3 pwms and all 3 irf6721, and short still there. Injected voltage on PR4004 right side based on schematic. I found out pu4003 is getting hot. replaced it with new one now short is gone.

Now I manage to salvage 3 used irf6721 which is good and replace all 3 just to make sure. Injected voltage again on PR4004 until 12v, and nothing is getting hot.

Now I returned resistor on PR4004 and inserted charger and boom. DCBATOUT is shorted again. but this time all ic that I replaced were not damaged.

I'm having trouble finding the short because I traced all DCBATOUT rail and none seems to be at fault. I don't know where to check anymore. I may have missed something. Any inputs? Much appriciated. Thanks.

[lezsimply]

Re: Lenovo Z570 directfet culprit

Further test revealed, PU4103 (dc5v,3.3v) of page 41 is getting warm on 19.25v and 0.004 amps. I already removed PU4101, PU4104 and all capacitor on pin no.16 VIN and its still getting warmer. I wonder where this ic draw its power to make it warm. The last thing I wanna do is remove this ic but I have no replacement for this as of now.

PS. It is warm because I can still touch the ic with my finger even for more than 5 mins.