Canon 300d will not power up

Well there is a few things to try first I think.
The camera is like a microwave owen, There is some switches that have to be closed properly. If only one of them fail to signal that it is closed the whole chain will be broken. Almost like an emergency stop on an machine.

Battery compartment switch, SD compartment switch and so on.
When you find one of these small switches try to "exercise it" (They are tiny).

Clean the lens contacts on both lens and camera with a "topz" (cottonstick) , gently do not rub.

Take out the battery..for an hour or 2 (Why not charge it full while waiting)

Start the camera up with the newly charged battery. Try to factory reset (not soft reset). (some canon cameras have a small "pinhole where you put something like a paperclip in to reset)

Try to update to the latest firmware if the camera will comunicate.

I guess there is a few more things to do before taking a walk to the reparshop.. but I can't remember it now.

This problem is not exactly unusual..
Totally dead and that the shutter quit working (black screen and pics) Seems to bee quite a problem all over the planet.

Have canon ever commented on this ?
Specially the 5x00 series seems to have the shutter problem going on.

Sorry for my bad English hope it's understanable anyway..

Stefan (Sweden)

No single fix im afraid, there are several fuses on the dc/dc converter that are worth checking, moisture on the flash board can fry them badly resulting in a dead camera.
basicly a dead eos is an eos with problems that wont allow the cpu to start, be it too much current being drawn somewhere, software issues or damaged ribbon cables.. risky business.

Best of luck