Well, I figured it out...? ?
I was pulling power off the 12v connector on the top of the board.? The only place to get a ground off the DC jack is on the side but it turns out that is not a real negative lead, it is open once you plug something into the DC jack.? So, my buck converter powering my nano was getting a ground backward, through the band pads, through the uC on the QDX, and through the Nano I was using for band switching my LPF kit.? I just killed my other (good) QDX.??
I figured it out by disconnecting my band wires from X6 and plugging in my LPF switching circuit alone.? It did not power up.? So I touched a band wire to a X6 pad and the circuit was powered.? I guess I'm putting in another order with Hans.
P.S.? I just noticed I called the microcontroller on the QDX an Atmel and it isn't; it's an STM.
Joshua
Joshua KJ7LVZ