@Sir Alex: On my USB to Serial Converter the pin power supplies are hardwired, so I can not supply directly. Nevertheless my levelshiter is a proven solution, so I do not expect any problems with it.
My problem is that I am not able draw 2mA from the 1.8V pin and that there is no acitity on the pins at all during boot or later. As I expland in my first posting I checked with an osziloscope.
So there is no need to acitvate something. hmm, I will check it again.