Lenovo Z50-75

[Jane]

The laptop Lenovo Z50-75 was dead. There was the first input mosfet (marked 4407) shorted. I replaced it; now, when I push On/Off button, CPU cooling fan starts for about a second and stops. Current( checking on power supply) goes to almost 0A.

What should I check next ?How to continue with the repair?
Thank you for help

[Sephir0th]

Re: Lenovo Z50-75

The board has a number you did not share and for Lenovo's there a often schematics available. You did not share any picture, any designation or measurement so far, so it is impossible to confirm from our side you've actually worked on where you assume you worked on.

Right now we have almost nothing to work with, except a mosfet model without any relation.

Regards

[Jane]

Re: Lenovo Z50-75

it is aclu7/aclu8 nm-a291 mainboard.
Picture enclosed

[Sephir0th]

Re: Lenovo Z50-75

I thought I made clear what we need to begin with proper troubleshooting. Do you have replaced PQ6? And if so, with which part (make/model)?

[Jane]

Re: Lenovo Z50-75

Yes, I replaced PQ6 with the same mosfet (4407).
When I connect mainboard to power supply ,RAM inserted, it takes about 28mA. ( without pressing power button).
When pressing power button ( by connecting pins on mainboard on GP2 connector),
current goes up to about 190mA and stays there as long as I am pressing the power button. As soon as I release it, the current drops to those 28mA.

Where can be a problem?
Thank you for help

[mcplslg123]

Re: Lenovo Z50-75

PQ6,pin4 voltage after replacing it? Standby consumption at 28mA seems bit high.

[Jane]

Re: Lenovo Z50-75

Pin 4(gateway) of PQ6 is 4.77V