TN panels usually work in normally white mode (it forms the picture by blocking unwanted colors from the backlight), so when you have a white screen on a monitor with TN panel, it is the panel which doesn`t work. Try checking the T-Con board for the voltages it needs to work(usually 5V); if there is a SMD fuse on the T-Con board, check it too; if the fuse is blown, check for shorted components before replacing it with an equivalent fuse(take care to notice components in parallel, especially the bypass capacitors).