thank you a lot for that information, orx65. you give me a hope.
is it really necessary to desolder the diodes first before measuring them?
i did the measurement already - you can see the values on the picture i got from all the diodes (more or less same values).
do all diodes have to show the exact same value? or is it not a problem when one diode shows 0,619 and other one 0,625?