This is a common problem on Amiga 3000 computers. The cause is battery leakage damaging the traces, corosion in the Denise or Amber IC sockets. The larger caps around the video circuitry could be going bad, or the Commodore Custom Video chip (near Amber) may be bad. I do not recommend installing boards in an Amiga 3000 computer, because the stock power supply is only 135 watts. Even though an Amiga 3000 has expansion slots, it was never really designed to be expanded. Commodore designed the Amiga 3000D as a graphics workstation. At the time, it had the most popular expansions as part of the motherboard- a proccessor board, a memory expansion board, a SCSI controller board, and a FF/SD board all on the motherboard. Commodore never intended for people to actually expand the computer further. When you do, you start having all kinds of problems. I have NEVER had any problems with a STOCK Amiga 3000. Add a graphics board and you will start having problems. BTW, most Amiga software does not need a graphics board, and many people install one because of pure ego.
I couldn't resist replying to this. That is the most ridiculous thing i have ever heard.. you must be doomy. 135W psu is plenty for quite a few expansions cards.The point that it DOES have expansion slots is why it is meant to be expanded. I have run many 3000's loaded with cards for many years with no troubles. as long as you keep it at a reasonable temperature its fine.
If anything many 3000's came with buster 7' chips which didnt support working zorro3 (you need buster9 or 11).
Ego? are you serious. gfx cards were useful for 24 bit stuff, many people wanted to see 24bit pics,surf the net in 24bit. It was a great improvement over slow ecs.
You can't really believe this silly nonsense you spread!
Mech