I have the Acer Laptop F5-571t. I have tried every 19V power supply I own for a series of other Acer products and none of them work. I even ordered a bag of DC 5.5x2.1mm Female to 5.5x1.7mm DC Plug Adapters to attempt to get a connector that exactly fits this F5 but all the laptop will do is detect the charger just as the plug goes in for a split second (brightening display) and then once the plug is seated, it goes to dim again and is no longer charging. Now the original power supply works and from what I have seen the plug size Acer is using on this laptop is 5.5mm x 1.7mm. I know I could order a backup power supply from Acer but I already have three 19V power supplies with the 5.5mm x 2.1mm for other Acer laptops that I no longer own, and I would like to use these old power supplies on the F5-571t