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Seems like there are a lot of occasions where it turns out that the MPU is fried. I've encountered it what, two or three times?

The MPU had to be working to put in the boot loader; what could subsequently damage the MPU in a normal turn-on? Is it always over-voltage on VDD, or is it exposing some other connection to the MPU to over-voltage?

And I suppose importantly: are there design changes that would better protect the MPU? (Not critiquing Hans' design, he's done more than I would've!)

73, Paul -- AI7JR

Hello Ken,

I suggest you separate all the boards and measure the resistance on the Vdd line of the main board.? If that is zero, you can do little other than check for shorts.? In my case, it was the MPU that shorted out.? The chip needs the QRP-Labs boot loader program to work, so replacing the chip is not yet an option, even if you can replace a large SMD device.

If the mainboard Vdd is not shorted, Check the other boards to see which one is the culprit.? I hope this is your case, as those are repairable.

73
Evan
AC9TU

-- 
Paul -- AI7JR