not turning on with PSU - Tested PSU and Jack

PSU 19.5v. Removed the jack plug from mother board and verified I was getting 19.5v there as well. Also plug the jack back into the motherboard and test for voltage by back pinning the plug when connected to the header. I was getting 19.5v and red to chassis I was also getting 19.5v. I then removed the battery and see if I was getting voltage on the battery terminals I getting 3v.

When running on battery when I remove the PSU the screen goes bright for a split second.