The sympthom: no sign of life by a 40d.
Repair: as the single fuse, which is in a 40d was ok, I’ve changed the DC-DC panel (unfortunatelly I had one from a dead body). After this, the body worked perfect.
I was very upset about this DC-DC panel, so I decided to investigate the bad part on the pcb. I opened the metallic shield – nothing to see.
A few weeks ago I’ve purcesed a small 10x/20x stereo micrscope – very good for soldering or to check a pcb. So I “scanned” the whole surface.
Do You see the problem? Between two pins of a tiny smd transistor (or what it is) there is a small tin-ball – produced by somebody who repaired the camera before. The ball was “glued” to it – or rather was welded to the pins.
Be careful by soldering a pcb!
And buy a good microscope (it was only 80 USD).