Sony G500 brightness problem

I have a Sony CPD-G500 monitor which was, unfortunately, dropped on the
floor (!). This blew the power supply, which has been replaced at the cost
of many $$$$. However, now the picture looks as if I turned the screen
control (there isn't one, by the way) all the way up, with raster lines and
all. There is a picture when hooked up to a computer, however.
The power supply is a new one from Sony.

Any help?
Thanks!
e @edsamail.com.sg