In addition to the other good advice presented, have you tried a different video output? (IIRC the A500 has 23-pin and RF only??)
TjLaZer wrote:
The green LED is the newer A500's, usually for ECS machines, ie 1MB Chip RAM capable, 2.04 Kickstarts, etc...
Yeah, I picked up one of these NIB a while back, green LED and the newer style "A500" sticker. (They seem to be a bit more rare here in the States.) It has v1.3 ROM installed, yet I do wonder if it has an ECS Denise or Agnus. Figured it wasn't worth breaking the warranty seals to find out.