Thanks for the new 10K trim potentiometer
I've fond finally some time to solder it.
I measured the old en new before i soldered the new one.
They gave the same result on the meter.
So , as i thought no better result, still at one point i've got visabillity, a hair too the right or left gives you a black or too bright screen.
I've looked at the site http://www.ladyada.net/make/monochron/newclock.html
they are all so bright and crisp on the screen, even your foto.
I can't get it so neat
I am eager to hear and try the next possible solution