Weird issues with A4000

[shovel]

I have a 4000/040 desktop that (apart from some minor configuration issues when first I got it) have been working just fine for many years.
At some point this week, something happened.

It started with workbench drawer windows freezing, and then freezing the OS completely. The system could be restarted by keyboard, but everything froze again when I opened any disk/partition window.

I was thinking that maybe there was something loose inside, IDE-connector, CF-card or such. So I opened the case and checked everything. I reseated a few connectors but couldn't really find anything distinctive.

I started the system again and could actually open disks, drawers and files. But suddenly the monitor went black.

Fast forward an hour and I came to the conclusion that the VGA output no longer works, and the audio output level is very low and heavily distorted. I can get video from the large video connector, connected to a TV via SCART, but the image is distorted with lots of horizontal lines. See photo.

I have tried taking every expansion card out (VGA, NIC and SCSI), but it makes no difference. I'm no expert on Amiga hardware and I'm clueless right now.

What happened here and are there anything I can do about it?

[shovel]

The battery was removed when I first got it, probably about 10 years ago. The remaining mess from the battery was later neutralized/cleaned up in 2015.

The capacitors were replaced in 2015, on both the main and CPU board. The CPU board also had some of them reversed, if I recall correctly. I think there were some CIA chips that got replaced too.


I still have the original PSU in original condition. I just measured the voltages at the PSU connector and they seem ok, with 12v being a little low at 11.9.

[shovel]

I can't determine what the SMD caps are but the thru-hole ones says nichicon.

The guy who did it wrote:

I use professional tools and supplies, and brand capacitors (Panasonic, Nippon Chemicon, Rubycon etc.).

[shovel]

Thanks for the information, I'll have a look at what was suggested above but I don't think I will be able to do any repairs myself.

The bottom case may have been slightly warped, a workshop had it some time ago to make some modifications and they weren't very careful. I will loosen all the screws and see if it makes any difference.

Not sure if this is one of the boards I've worked on previously or not, but either way, feel free to contact me for repair options if you can't figure it out.

http://amiga.serveftp.net

It was a guy in Denmark that did the previous work.
Where are you located?

[shovel]

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?)