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I believe all can be repaired thus far. I see no PCB damage.

I've purchased a handful of slightly under-rated fuses (20%). It was a matter of what was available more than anything.

Still waiting on the FETs to come in. At this point, the failure matches the blog suggested before (Q5/Q6 - with Q5 failing and not Q6).

I do not expect to get as lucky and have my debug end at this stage. I still suspect more issues.

From my initial measurements - I thought the voltage readings on the ICs were out of spec. However, ground reference changes (is not always chassis) - so absolute voltages based off of chassis ground are suspect. For ICs - better I measure GND pin to VCC rather than chassis to VCC.

That said, I plan on testing the ICs out of circuit. Will bread-board up a test circuit and verify function. Although I'm looking at bench supplies (w/var current limit and voltage) - those will take a while to purchase so I'll use a wall-wart and v-divs.

I'll also map out what I can for cascaded rails and try to lift all but the rails involved in 400V regulation. I need to isolate 400V and at least get that working without having to worry about failures down the chain.

At least once 400V is back up I can add the rest one by one until I blow a fuse (or not).

Of course, this process would seem more efficient if I stopped "blogging" about each step. I could edit out the messy parts. However, I believe it's instructive/useful to at least one future debugger to leave the warts in.