I just bought myself a nice condition PB 520c which was said to be working.

When I powered it on, it only showed white picture, so I guessed that the contrast must be off or something. I perhaps saw a very very faint picture in the background of the Mac OS loading screen. The contrast control doesn't react when pressed.

As I recently also got a PB 165 with similar problem (it needed new caps on the LCD panel), I was wondering if the 520c was also affected by this.

What should I try before opening it?