Weird issues with A4000

[Boing-ball]

You haven’t mentioned this but has the following been performed in the mainboard:

1).. Original Varta Barrel battery been removed?

2).. Have the Capacitors been replaced with new ones?

From what you are describing, makes me think you have failing Capacitors or a Leaking Varta Battery causing havoc.

[Boing-ball]

Capacitors replaced with good makes? I.e Japanese ones like, Panasonic etc..?

[Boing-ball]

Yep. Nichicons are a good make.

The only thing is if the corrosion is still present under the board layers and has started to spread causing connection problems.

Failing that, check for any loose chips in there sockets.

There maybe also an issue with board bend. Where the board is not sitting correctly in the case and causing connection issues.

[Boing-ball]

Well, still not sure what is going on. I loosened all screws holding the mainboard and made sure there was no tension in it.
Then I turned on the power and everything seemed normal again, including audio?

I will try to reassemble everything in steps, including all the zorro cards and see at which point the problem comes back, if it does. Like several people mentioned earlier, sounds like it could be some internal connection problem?

Also, what is usually recommended: keeping the original PSU and replace the capacitors or swapping it out for something newer (SFX/ATX?)

Sounds like Board bend and there maybe micro fractures or dry solder joints.I don’t think a PSU is going to sort this….

You can either get the board accessed for the issue. Or go one further and have the chips etc.. Transplanted onto a re-Amiga ACILL 4000 Motherboard.