you are brave to have done this but looks as if you may have found a good match
you may be able to counter the low contrast by a number of routes,
first use the RGB option in the menu to adjust each colour gain and cut off
i think there is a factory menu option but i can't remember how to access this on the 9400,it will be a combination of two buttons on the remote board-this will allow you to get a wider range of adjustment on the contrast etc
the issue could be a mismatch on the heater current,there is a adjustment pot that is sealed on the main chassis-this may sort out the issue but i have never adjusted this pot before so i do not know what will happen