Re: Lenovo P50 NM-A451 no power



Just ordered two rolls of the Kapton tape from mobilesentrix ($10+shipping) and from eBay ($7+free shipping) respectively for comparison. The 3M High-Temperature Flue tape will leave hard-to-clean glue residue behind. Just tried it on a scrap cell phone logic board....

Re: Lenovo P50 NM-A451 no power



I don't have Kapton tape on my hands, just 3M High-Temperature Flue Tape with heat resistance up to 600F. I'll look for the Kapton tape on mobilesentrix. Thanks for the tip....

Re: Lenovo P50 power-on issue



Sure. I just placed an order of 5 pieces of the PMOSFET from Mouser. I have an air gun. But I need to take some practice on how to remove the PMOSFET without blowing away the little capacitors surrounding the PMOSFET. I am looking for a scrap motherboard for this practice. Will post results here once I can safely remove the PMOSFET....

Re: Lenovo P50 power-on issue



I found the data sheet for the power P-channel MOSFET SI7149ADP-T1-GE3 and it shows that the Vgs threshold is between -1.2V and -2.5V. The PMOSFET will be on if the gate voltage is 1.2 to 2.5 volts lower. My measurement on the Vgs is 0 Volts, the Vgate to ground is the same as the Vsource to ground. So in other word, the gate and the source is connected to each other somehow. The only explanation to this is that the gate oxide on source side is punched through and gate/source connected to each other in some way.

Based...

Re: Lenovo P50 power-on issue



More update:

I measured the resistance across the capacitors PC4 (bottom side) and PC5 (top side) to be 431.7 KOhms and 427.8 KOhms, the capacitance to be 0.30uF for both respectively. In Diode mode, probing across PC4 positive to ground showing 2.27V and negative to ground showing open.

Thanks, Josh...

Re: Lenovo P50 power-on issue



1) Fuse PF1 ok ? DC IN should appear across the fuse on PF1, pin # 2

The continuity test shows the Fuse PF1 is good. DC-IN 20.64V appears on both ends.

2) MOSFET PQ1 - DC IN value should appear on pin # 1-2-3

DC-IN 20.64V on PQ1 pin # 1-2-3

Odd: DC-IN 20.64V on PQ1 pin #4, too

3) MOSFET PQ1 - DC IN value should appear on pin # 5 when powered up / ON.

DC-IN value on Pin # 5 is 0.042 V only.

I have no way to know if it is powered...

Re: Lenovo P50 power-on issue

Great! Here are the posts.

I followed your instruction and loaded ThinkPad P50's boardview file NM-A451 R10-0824.tvw. Let me know if I am doing correct. I need more help here on how to know what the voltage or resistance should be on a node of interest. See attached....

Hi,

My ThinkPad P50 laptops suddenly died on the docking station without any sign of life. I had to buy another P50 motherboard from eBay to get my work done. I just swapped the motherboard out and I am reusing everything including memory sticks, and hard drive, docking station, power supply, and battery pack. Now I have this dead motherboard. It has no LED light near the DC-in power jack with power supply plugged in. I get 19.95V at DCIN. I need this P50 BOARDVIEW to help me go further. I tried to download and install the P50 BOARDVIEW for debug. But the BOARDVIEW application Tebo-IctView.exe...