You can adjust the display contrast by using the
[CURSOR > ] or [CURSOR <] key while holding
down the [MENU] and [ENTER] key simultaneously.
Use the [CURSOR >] key to heighten the contrast.
Use the [CURSOR <] to lower the contrast.
You can reset to the default contrast setting by
pressing the [TIME BASE SELECT] key while holding
down the [MENU] and [ENTER] key simultaneously.
I quote from p28 of the User Manual. If this has no effect then the window is "shot".