Amiga 4000 boots and works on RTG but black screen on AGA

[Boing-ball]

What connection are you using for the native Amiga screen mode? (AGA). RGB 23pin connector? Or are you using a Scandoubler/Flickerfixer connected to the Lisa chip?

I do know the ZZ9000 with the video adapter port board should display a standard native Amiga display.
Has the Mainboard been recapped?

[Boing-ball]

So from what you describe. I’m thinking it’s something to do with the video side of things. I wouldn’t think it’s Kickstart or RAM or even CPU. Why? As you describe things seem to be working in the background, such a floppy disk appears to be installing workbench.

Have you tried completely stripping down the A4000 to just the Mainboard only? Even taking out the Daughterboard/zorro 3 board?

Then just plugging in a RGB to SCaRT to see if you get the kickstart screen.

[Boing-ball]

Any of the chips in sockets? If so try pushing down on them or lift out clean with contact cleaner or similar and then replace. Could be as simple as that.

[Boing-ball]

I see you are asking the same questions over here as well:

https://eab.abime.net/showthread.php?t=116568

What you have failed to mention on this thread you are getting AGA now and again. This to me looks to be a connection fault on the board. Possibly a broken trace or a faulty component with a dry solder joint.

I have come across when boards have been fitted in the A4K case, where if the board flexes or it’s grounding on metal where it shouldn’t, where these issues can occur.

As a tip. Ignore kin_hell as he hasn’t a clue…