Found the solution. The monitor seems to be very similar to the MAG DJ70.
Thanks to the repair tips at
http://www.e-repair.co.uk/tipsmon.htm !
The resistor R335 (220KOhm) near by the R318(220K) and Q302 in the power section
was defect. Replaced R335 - Monitor is alive again.
Bye and a happy new year 2005.