PowerBook 867 15 inch


Have a problem with an PowerBook 867 upon turning on it starts with a normal screen for a few seconds and reverts to a dark screen and continues to load as normal except for dark screen if I can find the curser I can change resolutions and the screen will return to normal for a second then revert, have tried everything but nothing works , have tried reseting (button under keyboard, removing battery holding down option and control with R P keys etc) but nothing fixes, I have noticed this has happened to others on this forum but I cannot seem to find the answer can anybody help?? Thanks tcharles