this week I received my cheap aliexpress usb to ttl converter..it did not work..
Then i found this video about using a arduino as usb to ttl converter.
https://www.youtube.com/watch?v=qqSLwK1DP8Q
Fortunately i had an old Arduino laying around

It works perfectly!
Notice that you have to connect the TXD>1 from the arduino to the TXD on your Toon
and the RXD<0 from the arduino to the RXD on your Toon.
(Arduino has a strange way to show where it's TXD and RXD sits on the board..)
Rooting my Toon went perfectly this way!
Thank you all for the great and usefull information on this forum.
Bart