[G4] Black Display/Sleep mode problem

[Roxylee]

Before taking my display to a repair shop, I thought I'd ask for  
advice here. I was given a 2002 DP MDD G4 running 10.5. pumped up  
processor and RAM, with an Apple LCD display. I ran the Apple software  
update  to 10.5.4. Everything was fine for a few days, then the  
battery started going, so I reset the time and date manually. The  
computer wouldn't connect to the internet until I reset time and date,  
then rebooted. This went on for a few days. I put it in sleep mode to  
avoid rebooting, and I think the display might be stuck in sleep mode,  
because while the power and brightness lights are on, (dimmed) the  
screen stays black. Unfortunately, the monitor on the kids computer  
has a different connection, so I can't hook it up to mine to test the  
computer. I tried the Apple LCD on theirs, with the same results. I  
have ordered a new battery, but have no idea if that will resolve the  
sleep mode problem, or even if that is the problem with the display.

  I tried various recommended key combinations and  the wake button on  
the keyboard, I unplugged everything overnight,  checked all  
connections, changed outlets in the surge protector, pressed the CUDa  
button for a second,  the cards are seated firmly. The display power  
button comes on and the screen remains totally black. When pressed  
again, the display power button won't power down the computer. Has  
anyone ever encountered this problem or does anyone have any ideas to  
try? Thank you in advance.:-)