After wiring everything up, verifying twice against the silkscreen and the manual, verifying that the power supply was 24v, I powered it up. Then the magic blue smoke came out.
The keen eyed reader will be able to spot the hole in the IC up and to the right of the 10 amp fuse.
There is also a crack in D1 on the DC Mode board. I'm not sure if the crack was there before or just a causality.
I contacted Big Tree Tech Support and they identified my error. The SKR 3-DC Mode board will fit in forwards and backwards and installing it backwards will cause catastrophic damage to the mainboard. It is a bit of a design failure that the board can be installed backwards, and that backwards is destructive. In fact, installed the board correctly covers the BOOT button. By simply adding 2 dummy pins to one of the connectors would provide an indicator of the proper orientation without requiring much additional board work.
Isn't it clear in the manual? Well, it is more complex then that. I suffer from Protanopia (red/green colorblindness). While the manual explaining the proper orientation of the board may be quite clear to you folks with normal color vision.
It is quite a bit less clear to those with less than normal color vision. Here is an approximation of what I see:
The board fit so perfectly in backwards I didn't even bother to try to figure out what was written in red on the diagram.
Where does the responsibility lay in a case like this? Should manufactures be required to check that their manuals are clear for that 1% of us that can't see the colors properly? No, that would be silly, I've grown up with this condition, I know better, I have software on my computer to assist, this is not something we need a campaign to resolve.
Should hardware be designed not to explode when a part that fits better backwards than forwards is installed incorrectly, I think that would be nice.
Oh well, I know what went wrong. The problem is all between the chair and the work bench.
I'll be ordering some replacement hardware in the next few weeks and give it another try.