How to use UltraSlim power supply with W520
The W520 is shipped with a 170W power supply. But if you measure the power that is pulled out of the 230V wall socket it's less than 90W in many situations. So you might want to use the 90W UltraSlim power supply. You can do this, but whenever the W520 is switched on, it tells you that the power supply does not deliver enough power, and the power supply is not used at all.
So let's see how the W520 knows that you are using the 170W power supply.
The power supply plug of the W520 has three contacts.
1. outside: ground 2. inside: power 3. middle pin: signal
The resistance between the the signal pin and the ground pin is ?? Ω. (You can measure this with a standard multimeter).
Now you can open the tip of the UltraSlim power supply. There the middle pin is not connected at all. But there is a place for a resistor on the pcb, which is not mounted. What you have to do is connect the middle pin to the pcb and place a ?? Ω resistor at the right place.
If you now use the UltraSlim powersupply the W520 thinks that it is a 170W power supply and uses it. But be carefull! Do not consume more than 90W!