Philips car 400 radio display?

Hello everybody:
The dash digital display on my 1999 Corsa B won't work while radio (Philips car 400) is on (clock and outside temp Ok).
It works fine when setting the Code and its shows the date when off, but when on...lights out (Clock and temp still work)
What do I have to fiddle? Radio? Display? Wiring?
Anyone else here had the same problem?
Best regards