Dear David,
I am glad you are seeing some progress. As best the reports say, shorting the VDD to ground will not necessarily kill the 3.3v switching supply. So hopefully, you don't need a new PCB #2.
So... you were able to load the firmware which means the linear regulator of PCB #2 must be ok, which is connected also to VDD. Otherwise, the processor would not be able to boot. Now that you loaded the firmware, the processor is now trying turn on the switching part of VDD (or at least this is my understanding). But I wonder about your measurement check of VDD. You report 2.5v on VDD and a resistance (without power, of course) of 0.4 ohm. That would be I = V/R or 6.25 Amps. So I wonder about that resistance check and I'm not seeing on the schematic how that would make sense. You can unplug the switching board PCB #2 and measure the resistance again.
Are you possibly using a current limited supply which is not able to provide the current necessary for full boot up? Remember the linear regulator is also connected (but get's disabled at some point in the boot process) so the VDD onto the main board should definitely not measure so low as 0.4 ohm, Otherwise I don't think you would have been able to load the firmware.
73,
Gregg W7GRM
