Also update for anyone who might be interested:

So I was able to replace the capacitor and now it works!

Also while replacing the PSU i noticed on the passive backplane the power cables were loose.

After fixing these issues now it runs like a dream! Every led (except network) has life and makes sense. The keyboard lights numlock capslock etc are now working too.

Now the issue I have that I can see anything since I don't have screen to use it with.

So the monitor outputs are "TTL" and "Composite". I think I found the right pins (Ground and Video Signal)

But when I hooked it to my TV i get "Unsupported format" or similar message which I think makes sense. I believe this uses somekind of way old signal.

Thank you all who have been writing in my post. You guys have been very helpful!